Bulletin of the Global Volcanism Network

All reports of volcanic activity published by the Smithsonian since 1968 are available through a monthly table of contents or by searching for a specific volcano. Until 1975, reports were issued for individual volcanoes as information became available; these have been organized by month for convenience. Later publications were done in a monthly newsletter format. Links go to the profile page for each volcano with the Bulletin tab open.

Information contained in these reports is preliminary at time of publication and subject to change.

 Bulletin of the Global Volcanism Network - Volume 39, Number 05 (May 2014)

Managing Editor: Richard Wunderman

Kilauea (United States)

During 2013, a summit lava lake and lava flows on slopes and into ocean

Nabro (Eritrea)

Thermal alerts ended mid-2012; revised 2011 plume heights; uplift mechanisms debated

Pacaya (Guatemala)

Sudden, bomb-laden explosions of 27-28 May 2010; extra-crater lava flows


United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local

During 2013, a summit lava lake and lava flows on slopes and into ocean

This report summarizes observations and monitoring data from Kilauea during January-December 2013; activity during 2010-12 was covered in BGVN 38:05. The primary reporting source was the U.S. Geological Survey-Hawaiian Volcano Observatory (HVO) which provided monitoring and communication resources for the Hawaiian volcanoes, namely Kilauea, Mauna Loa, Mauna Kea, Hualalai, and Lo`ihi.

2013 Overview. During 2013, Kilauea's summit lava lake persisted , and lava flows erupted from Pu'u 'O'o. Two minor ocean entries were visible during the year until mid-July; both were branches of the Peace Day flow while, later in the year, two lava flows (Kahauale'a 1 and Kahauale'a 2) extended N-NE from Pu'u 'O'o. Both lava flows crossed into the nearby forest, causing fires and significant smoke along their margins. Petrology of the summit tephra and East Rift Zone (ERZ) did not show significant changes during the year. SO2 emissions from both, the summit and the active ERZ were closely monitored by HVO and those observations led to new innovations in quantifying the flux. HVO reported that SO2 and also CO2 fluxes were relatively low but still above safe levels as established by the Centers for Disease Control and Prevention. Flank deformation and seismic monitoring determined that, although variable conditions were detected, very little accumulated change had occurred at Kilauea.

Due to the Federal shutdown during 1-16 October 2013, HVO focused on only the most critical operations. Activities that were not directly related to critical operations were postponed, including research and outreach.

One such outreach opportunity that became curtailed was the first Great ShakeOut for Hawai`i which took place on 17 October 2013 and included almost 16,000 participants across all of the islands. This was a large-scale earthquake drill that followed in the tradition of The Great Southern California ShakeOut, which took place in 2008. HVO partnered with the State and County Civil Defense, Center for the Study of Active Volcanoes (CSAV), National Oceanic and Atmospheric Administration (NOAA), University of Hawai`i (UH-Hilo), American Red Cross, and FEMA. HVO staff generated a significant amount of information for the media including several press releases and web content; they also attended preparedness fairs and gave public talks.

Persistent thermal anomalies during 2013. More than 200 alerts per month were released by the MODVOLC program during 2013 for the Big Island of Hawai`i (figure 211). These alerts came from sites around the island that exhibited elevated radiance and were dominated by Pu'u 'O'o and the Kilauea summit. One exceptional thermal anomaly was a site along the Mamalahoa Highway (Highway 190) in the NW sector of the island. News sources reported that, during 25-26 November 2013, a significant brushfire burned 300 acres in South Kohala. The burn site was near the highway mile marker 14 and caused segments of the highway to close while emergency crews contained the fire.

Figure 211. More than 200 thermal alerts were posted each month in 2013 by the MODVOLC program for the island of Hawai`i. This image captures the thermal alerts registered during January-December 2013. Note the concentration of red-to-yellow thermal alert pixels at the summit of Kilauea and at the Pu'u 'O'o vent along the E rift that also reached the sea. The anomalous pixel located N of Hualalai (green box) was attributed to a fire that burned near Highway 190 during 25-26 November 2013. Courtesy of MODVOLC.

Summit lava lake activity. "Now in its sixth year, the current summit eruption harks back to the persistent lava lake in Halema`uma`u during the 1800s and early 1900s, suggesting that it has the potential to last for many years" (Patrick and others, 2013). Based on Hawai`i's written record, one earlier summit lava lake occupied Halema`uma`u during 1823-1924.

During 2013, the summit lava lake within the Overlook crater, a nested crater within Halema`uma`u, fluctuated in height, by tens of meters, resulting in perched lava deposits (bathtub rings) and collapse of the crater walls. The crater englarged slightly as a result.

Also, observers frequently noted nighttime incandescence (figure 212). Local webcameras (infrared and visible-light) captured images of the lava lake from the Halema`uma`u Overlook site as well as from the highest point of the HVO facility.

Figure 212. During 2008-2013, an active lava lake resided within the Overlook crater, a feature within Halema`uma`u crater at Kilauea's summit. A) This shaded relief map indicates where HVO installed a thermal camera (HT cam) to view the entire surface of the lava lake. HVO and the summit tiltmeter (UWE) are 1.9-2.0 km from the lava lake. B) This oblique view is an aerial photo of the SE crater rim of Halema`uma`u. Modified from Patrick and others (2014).

The HT infrared camera occasionally documented crater rim collapse events in 2013. These events were relatively small-sized and tended to occur more frequently when the lava lake level was relatively deep within the Overlook crater (for example, a small collapse occurred when the lava lake was at a depth of ~75 m during 25-26 July 2013). When the lava lake was high, however, the interior walls were subjected to heating and cracking and HVO scientists concluded that collapse events could be triggered during these conditions as well. One collapse event, on 15 November 2013, was likely triggered by slumping due to heavy rain; several Park Rangers observed the event and the collapse was heard by an HVO scientist standing at the Jaggar Overlook (the same location shared with HVO on the crater rim).

A crust of lava had formed an inner rim within the Overlook crater and, on 25 July at 2033, a portion of that rim collapsed into the lava lake (figure 213). The main event was followed by smaller collapses of the deep inner ledge during the following day. Based on webcamera images, explosive events were not triggered by the collapse. HVO reported that, since the formation of the lava lake (March 2008), the largest gas-and-ash emissions from the summit were triggered by gravitational collapses along the crater rim; when rockfalls hit the convecting lava's surface, violent gas release could occur.

Figure 213. These two thermal images were taken before (25 July 2013) and after (30 July 2013) the collapse of the inner rim of Kilauea's Overlook crater. The inner rim had been constructed during high lake levels in October 2012 (~22 m below the Halema`uma`u crater floor). The webcam (HT cam) was located on rim of Halema`uma`u crater and it captured a new image every ~15 minutes; the temperature scale is in degrees Celsius up to a maximum of 500°C and it automatically scaled based on the maximum and minimum temperatures within the frame. At the time of these photos, the surface of the lava lake was ~75 m below the Overlook crater rim. Courtesy of HVO.

According to HVO, the lava lake level within the Overlook crater generally fluctuated 30-60 m below the rim during 2013. A laser rangefinder was used to obtain regular measurements during the year. Lava was closest to the rim and flooded part of the inner ledge of the crater in January 2013 (an event that also occurred in October 2012). Lava at the flooded lake's margin chilled and reinforced the bathtub-like ring that persisted above the active lava surface (note the "inner rim" in figure 213). In daily online reports, HVO noted: "The lake level responds to summit tilt changes with the lake generally receding during deflation and rising during inflation."

Starting in 2009, HVO scientists noted rise/fall events and determined that the pattern began with decreasing tremor from the summit at a time when lava rose within the lake, spattering would decrease or completely stop, and summit tilt would also decrease. "After a period of minutes to hours, the lava will abruptly drain back to its previous level amidst resumed vigorous spattering, seismic tremor amplitude will increase for a short time (a seismic tremor burst) before resuming background levels, and summit tilt will return to its previous level. Gas emissions decrease significantly during the high lava stand (the plume gets wispy), and resume during its draining phase. Taken together, the geophysical characteristics suggest that, during the high lava stand, lava is puffed up with gas trapped under the lava lake crust."

During 2013, explosive events at the summit rarely occurred; intermittent spattering and degassing dominated summit activity. The plume from the vent continued to deposit variable amounts of ash, spatter, and Pele's hair onto nearby areas, particularly downwind of the crater (figure 214). The Overlook crater diameter was 35 m in March 2008 and, by the end of 2013, the dimensions had increased to 160 x 215 m. The size increase followed minor explosions and rockfalls from the interior crater walls.

Figure 214. Pele's hair (fine strands of natural glass) continued to accumulate downwind of Kilauea's active summit crater. A) This photograph from 3 May 2012 was taken looking along the curb of the Halema`uma`u parking lot (closed to the public since the onset of summit activity in 2008), and shows a mat of Pele's hair accumulated on the windward side of the parking curb. Courtesy of Matthew Patrick, USGS. B) On 9 December 2013, a continuous carpet of Pele's hair was observed shining like gold near the Halema`uma`u Overlook trail next to the parking lot. Courtesy of Ben Gaddis, USGS.

Kilauea's Overlook crater lava lake produced a small explosion during 2148-2149 on 23 August 2013 (figure 215). A portion of the overhanging SE crater rim collapsed and struck the surface of the lava lake. The debris had fallen into an area where nearly persistent spattering had previously been observed. The ensuing explosion generated a plume containing ash, lapilli, bombs (up to 34 cm in diameter), and lithics (ash, lapilli, and blocks up to 10 cm in diameter). The plume deposited material across the Overlook area. The level of the lava lake had been measured as ~38 m below the rim of Halema`uma`u crater earlier that day. Normal conditions prevailed after visibility returned within the camera's field of view at ~2149.

Figure 215. Images captured between 2148 and 2149 on 23 August 2013 by the HT camera (see figure 212 for location) during a small explosion from Kilauea's lava lake. The thermal images A-D highlight the incandescence that persisted from the lake's surface as well as the hot spatter and debris that exploded after a portion of the inner crater rim fell into the lava lake. Courtesy of HVO.

Pu'u 'O'o and East Rift Zone lava flows. The Pu'u 'O'o eruption consisted of three lava flows during 2013: the Peace Day, Kahauale'a, and Kahauale'a 2 flows (figure 216). The Kahauale'a flows were unique in that they traveled N of the rift zone, unlike the numerous other lava flows that have spread generally toward the ocean (including the Peace Day flow) (figure 217). This activity was considered the continuation of Episode 61, which began on 20 August 2011 and continued through the end of this reporting period (December 2013).

Figure 216. The "spillway"—Pu`u `O`o's eastern flank—has been buried by flows fed mostly from a spatter cone on the NE side of the crater floor. Most of the dark-colored lava in the foreground is new lava that has resurfaced the spillway during the past year. The fume to the left is the trace of the Peace Day tube which carried lava to the coast and had been covered by lava flows from the crater . The tube carrying lava to the NE is inconspicuous, but extends toward the lower right side of the photo. Photo taken on 25 February 2013. Courtesy of HVO.
Figure 217. Geologic map of Kilauea's East Rift Zone and lava flows from the active vent, Pu`u `O`o. The distribution of lava flows emplaced during 2013 is shaded red (bright red, pink, and red-orange). The yellow lines extending from Pu`u `O`o represent the general path of lava tubes that directed the flows Peace Day, Kahauale'a 1, and Kahauale'a 2. Changes to the surface area of the Kahauale'a 2 and Peace Day flows are shaded bright red, corresponding to activity during 19 September-26 December and 19 September-2 November 2013 respectively. Note that Kahauale'a 1 was active during 19 January-17 April 2013. Courtesy of HVO.

The morphology of Pu'u 'O'o crater was relatively stable through 2013. The crater remained very shallow and at or near the level of the original E spillway rim (figure 216). There were four spatter cones, all consistently active and often exhibiting incandescent openings at their tops (figure 218). These cones also emitted gas-jetting sounds and occasional, effusive spattering. The main center of activity through the year was the NE spatter cone. This cone often hosted a small lava pond and served as the vent for the Kahauale'a and Kahauale'a 2 flows.

Figure 218. A small lava lake, several meters in diameter, had persisted for nearly a year on the NE side of the Pu`u `O`o crater. The lake was perched several meters above the surrounding crater floor (seen behind the topographic high, shrouded in steam). The feature was near the top of a mound of lava composed of spatter cones and lava lake overflows. Flows from the lake and other nearby spatter cones had inundated the E rim of Pu`u `O`o's crater, which would normally be visible in the background just behind the area seen here. Photo taken on 31 January 2013. Courtesy of HVO.

In late 2012, Pu'u 'O'o crater was slowly infilling, and by the beginning of 2013, lava from the NE spatter cone reached the E spillway rim. A dramatic inflation event in mid-January triggered numerous overflows from the NE spatter cone, and the SE cone spread more lava across the crater floor but also sent flows over the E spillway. On 19 January, an overflow from the NE spatter cone sent lava down the E spillway in what would become the Kahauale'a flow. Over the next month, overflows from the cone covered much of the E spillway. Inflation in late April correlated with abundant venting and more overflows from four cones on the crater floor, with some spilling out toward the E, adding to the recent flows mantling the upper E flank of Pu'u 'O'o (figure 219). After the Kahauale'a flow eventually stalled in April, overflows in early May from the NE spatter cone fed a new flow, following the same course; this became the Kahauale'a 2 flow. Small overflows occurred sporadically from the cones through the remainder of the year, with larger events in mid-August and mid-November.

Figure 219. This thermal image of Pu`u `O`o was captured on 27 November 2013. The SE and NE spatter cones had produced small flows that extended out of the crater, shown clearly here by their warm temperatures. The vent for the Kahauale`a 2 flow is at the NE spatter cone, and the lava tube supplying the Kahauale`a 2 flow is obvious as the line of elevated temperatures extending to the lower right corner of the image. The distance between the black scarps is ~ 300 m. Courtesy of HVO.

Coastal plain lava flows and ocean entries. The Peace Day flow (episode 61b) began on 21 September 2011, and it was active for much of 2013 before ceasing in November 2013. This lava flow reached the sea and generated scattered, branching flows (breakouts) on the coastal plain, as well as several isolated breakouts above the pali (fault scarp).

The ocean entry consisted of two main entry points during 2013, with an E entry at Kupapa`u (just E of the Park boundary) and a smaller, weaker entry immediately to its W (within the Park). These entry points were not vigorous; there were little-to-no-observed littoral explosions; a delta formed that extended several meters out from the sea cliff (figure 220 A).The view from the E margin of the Peace Day flow field on the sea cliff was relatively good, and the ocean entry provided a destination for guide services (not all sanctioned) operating out of Kalapana (numerous, possibly over 100 tourists made the hour-long walk out to the site each evening). As activity on the coastal plain declined in the summer, the W entry shut down in mid-July; the E entry ceased on 21 August.

Figure 220. Thermal images have helped HVO geologists map Kilauea's lava tube system. (A) This thermal image from 27 June 2013 shows Kilauea's E ocean entry (spanning ~ 1 km along the shore) at Kupapa`u Point. Just inland from the entry point a patch of slightly warmer temperatures indicates an area of recent small breakouts. Inland from this warm patch you can see a narrow line of elevated temperatures that traces the path of the lava tube beneath the surface that is supplying lava to this ocean entry. Two plumes of higher temperature water (~50°C in areas close to the ocean entries) spread out from the entry point. Courtesy of HVO. (B) This image shows the Peace Day lava tube coming down the pali in Royal Gardens subdivision on 24 May 2013. The lava tube parallels Ali`i avenue (see figure 217 for the location of Royal Gardens), shown by the straight line of warm temperatures that represent asphalt heated in the sun. This tube feeds lava to the ocean entry and breakouts on the coastal plain. There is no active lava on the surface in this image - the warm surface temperatures are due to heating by the underlying lava tube. Courtesy of HVO.

Most of the Peace Day flow activity during 2013 was constrained to the coastal plain. From January through August, the coastal plain featured episodic of breakouts near the base of the pali in Royal Gardens. Those branches from the main flow slowly migrated toward the ocean before halting on the coastal plain (figure 220 B). Eventually, another breakout occurred at the base of the pali and sent out another flow that presumably drained supply from the previous flow. The new flow reached the location of the stagnating previous flow, and the flows became an indistinguishable mix of small, scattered breakouts in the middle of the coastal plain (figure 221). Minor, scattered breakouts were common on the coastal plain during January-August. Activity levels declined by August, the ocean entry diminished, and the last coastal plain flows ended around 8 September. With no ocean entry or surface flows, the coastal plain (and Kalapana-based lava tourism) became quiet again.

Figure 221. Lava flows from Pu'u 'O'o consisted of only a few scattered breakouts near the shoreline on 18 January 2013, with most of the activity focused on the coastal plain closer to the base of the pali. This pahoehoe lobe (~1 m wide) was active near the E margin of the Peace Day flow field just a few hundred meters from the coastline. Courtesy of HVO.

Lava flow activity above the pali. From mid-January to the end of May 2013, a large amount of lava escaped the Peace Day tube to create a divergent flow above Royal Gardens. It did not advance very far until April, when it crept slowly downslope into the upper reaches of Royal Gardens. This breakout flow ceased on 30 May. As the coastal plain breakouts progressively decreased during September, two small flows appeared above the pali, presumably resulting from the abandonment of the lower Peace Day lava tube. The smaller of the two breakouts was at the top of Royal Gardens, about 6 km from Pu'u 'O'o, and appeared to start between 7 and 14 September but was inactive by mid-October (timing was determined in large part by satellite images as opposed to direct observation). This small breakout flow was visible from the Kalapana lava-viewing area.

The larger of the two breakouts began around 5 September and was about 3 km SE of Pu'u 'O'o, advancing a little over a kilometer before stalling. This breakout was active until 7 November, when it and the rest of the Peace Day flow stalled. This wasn't the end, however, and the Peace Day flow gasped a final breath when a very small, brief breakout occurred on the upper Peace Day lava tube, near Pu'u Halulu, on 15 November. It was probably active for only minutes or hours and marked the end of the Peace Day flow.

The Kahauale'a flow (episode 61c) began as an overflow from the NE spatter cone on 19 January 2013, occurring simultaneously as Kilauea inflated. It advanced down the NE flank of Pu'u 'O'o, N of the Peace Day tube, until it hit flat topography N of the cone where it developed a lava tube and covered early Pu'u 'O'o 'a'a flows. The flow consisted of scattered pahoehoe lobes, and these migrated slowly (~50 m/day) E toward Kahauale'a cone, reaching it in mid-February (figure 222). From there, it followed the N margin of an earlier flow emplaced during the episode 58 flow. The path of this new flow abutted the steep northern slope of the 2007-2008 perched lava channel. This confinement led to a narrowing of the advancing flow front, resulting in increased advance rates (>100 m/day) in early March. As the front passed the perched channel, it became less confined, and advance rates dropped to under 50 m/day. By the first week of April, the flow had reached 4.9 km from the vent on Pu'u 'O'o but ceased on 17 April during a deflation-inflation (DI) event (see figure 199 in Bulletin 38:02 where DI events are illustrated). Due to infrequent overflights by HVO scientists during 2013 (resulting from budget cuts), staff relied heavily on satellite images--particularly EO-1 Advanced Land Imager images--to track the advance of the flow.

Figure 222. Kahauale`a Cone, a local topographic high several hundred meters long, has long been a small oasis of vegetation in the midst of Pu`u `O`o lava. This photo from 19 March 2013 shows new lava from the active Kahauale`a flow surrounding the cone, which has also partly burned. Vent structures (such as episode 58, active from 2007 to 2011), are in the background just behind Kahauale`a. Pu`u `O`o is out of sight to the right. Courtesy of HVO.

HVO noted that the Kahauale'a flow was unusual in that the most recent flows from Pu'u 'O'o traveled S toward the ocean, providing minimal threat to residential areas. The Kahauale'a flow, however, was directed N of the rift zone, along a NE trend. This put the flow on a downslope trajectory that could have threatened residential areas of including Ainaloa and Paradise Park. HVO and Hawai'i County Civil Defense increased their communications through that time period but just a few weeks later, in mid-April, an abrupt change in magma supply occurred at Pu'u 'O'o and the flow ceased.

Inflation at Pu'u 'O'o produced another overflow from the NE spatter cone, which started on 6 May. This became the Kahauale'a 2 flow (episode 61d) and was directed slightly more to the N by the original Kahauale'a flow, reaching the forest boundary ~2 km NW of Pu'u 'O'o in early June. These flows invaded the forest a short distance and created steady forest fires. During July, the flow front took a more northeasterly course, following the N margin of the original Kahauale'a flow (figure 223). Its advance slowed during late July to mid-August, but during September the advance increased when the flow entered the previously mentioned narrow channel along the episode 58 perched lava channel.

Figure 223. (top) A photo taken looking W from a helicopter on 19 September 2013 of the burning forest due to Kilauea's Kahauale`a 2 flow (approximately 7 km long). This lava flow extended from Kilauea's Pu'u 'O'o NE vent. Active breakouts on the Kahauale`a 2 were scattered over a broad area. Here, a breakout near the edge of the forest engulfed trees and burned dead foliage. Courtesy of HVO. (bottom) The flow front of the Kahauale`a 2 flow cut a narrow swath through forest NE of Pu`u `O`o. The narrow lobe at the front was inactive at the time of this photo on 27 November 2013, with the main area of surface flows about 2 km behind the end of this lobe. Some of these surface flows slowly expanded N into the forest, igniting fires. Pu`u `O`o is in the upper left, ~7 km SW. Courtesy of HVO.

By mid-October, Kahauale'a 2's narrow flow front had reached the distant forest boundary and surpassed the length of the original Kahauale'a flow. A narrow finger of lava forming the flow front advanced into the forest in mid-November, reaching just over 7 km distance from Pu'u 'O'o, before stalling soon after 20 November. Behind the flow front, branching flows began to migrate along a more northerly direction into the forest, triggering more fires. This area of breakouts soon turned NE, paralleling the narrow finger that had stalled in late November. By 26 December, the active flow front was 6.3 km NE of the vent and persisted into the New Year.

Petrology of the summit (Halema`uma`u) and rift (Pu`u `O`o) lavas. From 2013 to 2014, the juvenile component of Kilauea's summit tephra remained essentially as it had during 2008-2013. The overall temporal variation of summit lava mimicked the MgO systematics of ERZ lava for the 2008-2014 interval, with summit glass compositions overlapping those of contemporaneous bulk ERZ lava but erupting 20° to 25°C hotter than at Pu'u 'O'o. There were no changes in trace-element signatures, which matched those of the East Rift Zone (ERZ) lava. Halema'uma'u vent tephra remained sparsely olivine and spinel phyric with ~2 volume percent of 100-300 μm, subhedral to euhedral olivine phenocrysts (typically with melt inclusions). Olivine in summit glasses was consistently complemented by >0.05 volume percent of chromian-spinel microphenocrysts.

2013 Pu'u 'O'o lava also did not show any significant petrologic changes. It contained a five-phase assemblage: olivine(-spinel)-augite-plagioclase-liquid. The assemblage was interpreted as the result of simultaneous growth and dissolution of phenocrysts, reflecting the modeled values for cooling, fractionation, and mixing in the shallow edifice prior to eruption. This multi-phyric condition (see figure 224 for photomicrograph examples from previous years), which had persisted in the steady-state ERZ lava for most of the last ~15 years, attested to a stable shallow magmatic condition perpetuated by near-continuous recharge and eruption.

Figure 224. Two photomicrographs of Pu'u 'O'o thin sections sampled by HVO scientists from vent (a) and lava tube activity (b) during 1996-1998 (100 μm = 0.1 mm). Both show glass containing olivine phenocrysts with melt inclusions and opaque microphenocrysts of spinel. Image B shows an olivine phenocryst and spinel microphenocrysts in glass with round vesicles (one is located behind "b"). Modified from Roeder and others (2003).

SO2 emission rates. During 2013, HVO reported notable advances in measuring the dense, opaque summit SO2 plume. It was significant to note that the summit SO2 emission rates measured since 2008 represented a minimum constraint on emissions, whereas by the end of 2013 it was possible to determine a more accurate estimate of the amount of gas emitted from the Overlook crater. Because traditional gas measuring techniques are subject to multiple scattering effects from incoming radiation that can contribute to significant errors in the calculated SO2 emission rates, HVO scientists were pursued various approaches to achieve a more accurate emission rate.

HVO scientists addressed the issue of underestimation due to scattered light in two ways: (1) minimize and/or model the effects of scattering on the retrieved results and (2) measure farther away from the emission source where the plume is more dispersed and not as optically thick.

Using HVO's old metric for evaluating SO2 summit emissions, the total SO2 released in 2013 was first calculated as 266,000 metric tons. They had long recognized these value as among those that had persistently understated the true mass of SO2. To account for the summit emission rate underestimation, they used an initial preliminary correction. It was based on early Simulated Radiative Transfer- Differential Optical Absorption Spectroscopy (SRT-DOAS) values. This refinement increased the summit's traditional estimate 3-fold, yielding a summit total SO2 amount of ~800,000 metric tons for the year 2013.

HVO further reported a preliminary calculation of Kilauea's 2013 summit emissions using their available Flyspec array data yielded ~1.0 x 106 metric tons for 2013. This was judged more accurate value for the total summit SO2 release.

East rift zone (ERZ) emissions for 2013 continued at the low level recorded since mid-2012. Early in the year, SO2 emissions increased coincident with the occurrence of the Kahauale'a lava flow, but emissions stabilized several months later and continued at a low level for the balance of the year. Rift emissions were consistently less than those at the summit for 2013 totaled ~113,000 metric tons (using the refined methods mentioned above). This was ~20% less than reported in 2012, and the lowest amount recorded since the ERZ eruption began in 1983. The low SO2 emissions from the ERZ were at least partially due to degassing at the summit.

Summit CO2 emission rates. During 2013, CO2 emission rates remained at the relatively low level measured since approximately 2009 (figure 225). The continued absence of a strong CO2 signature in 2013 confirmed that the current summit activity reflects shallow reservoir processes rather than deeper ones. All CO2 measurements in 2013 were made with the Licor LI-6252 gas analyzer.

Figure 225. Daily average CO2 emissions from the summit of Kilauea, as measured under trade-wind conditions, during 2003-2013. The vertical bars represent standard deviations of all traverses on a single day. The cyan symbols show CO2, calculated using filtered data to more confidently bracket CO2 emission rates. The black squares are raw CO2 area-count averages; these values provide a measure of CO2 independently of the C/S ratio and SO2 emission rates by accounting for the area traversed through the plume and integrating that area by gas concentration magnitudes (this method also takes into account the plume direction and speed). CO2 values were calculated without any correction to underestimated SO2 emission rates. Courtesy of HVO.

Quantifying summit and rift plume characteristics. In addition to emission-rate studies, HVO continued to monitor the summit and rift plumes using a variety of techniques, including multi-species sensor-based time-series measurements and open-path FTIR. In 2013, FTIR measurements of the summit plume reconfirmed the shallow nature of the degassing source, with plume chemistry characterized by low CO2, high SO2, high H2O, and significant HCl and HF (table 9). Measurements of the summit and rift plumes yielded similar chemistry, suggesting a common source for these gases. Also reconfirmed in 2013 were the previously observed short-term changes in gas chemistry correlating with behavior in Overlook crater.

Table 9. The composition of Kilauea's summit plume for 2013 reported in moles and mole%. Courtesy of HVO.

Gas species moles mole%
H2O 1,117.98 88.23
SO2 81.46 6.43
CO2 64.69 5.11
HCl 1 0.08
HF 1.17 0.09
CO 0.84 0.07
total moles 1,267.14 100

Gas hazards. In 2013, the maximum ambient concentration of SO2 measured near the summit along Crater Rim Drive during traverses made with a car was 150 ppm, a value well above the IDLH (Immediately Dangerous to Life and Health) threshold. Concentrations measured inside the vehicle reached a maximum of 12 ppm. The inside-car levels were measured with all air-handling turned off, the operating conditions that minimize SO2 penetration into the vehicle. Fumarole sampling at the two locations on the rim of Halema'uma'u were subsequently paused during 2013 while shifting to alternative, less-hazardous measurement techniques.

HVO continued to operate the low-resolution SO2 sensor and rain collector network on Kapapala Ranch in 2013 (within 23 km SW of the summit). In general, maximum SO2 concentrations on the Ranch in 2013 were lower than in 2012. During the early years of the activity at the Overlook vent, the Ranch's livestock exhibited runny eyes, respiratory issues, weight loss, and tooth mottling and degradation (possibly indicating fluorosis). Additionally, fences and other metal infrastructure on the ranch had been deteriorating more rapidly than before the summit eruption began. New data showed SO2 one-minute values for 2013 (a single, one-second measurement per minute) up to 4 ppm. Hazard monitoring and communication with the ranch operators, veterinarians, and public health officials remained ongoing.

Ambient SO2 concentrations measured downwind of Halema'uma'u continued to reach very high levels (~150 ppm) along Crater Rim Drive near the Halema'uma'u parking lot, warranting continued caution along Crater Rim Drive in 2013. HVO scientists maintained communications with community groups and county, state, and federal agencies in order to relay the changing gas-hazard conditions associated with Kilauea's ongoing eruptions.

In 2013, the National Park Service's (NPS) ambient air quality stations located at HVO and behind the Kilauea Visitor Center continued to record periods of hazardous air quality resulting from the ongoing eruptions. The National Park continued to close the highly impacted areas of the park during poor air-quality episodes. Closing of park locations, including Kilauea Visitor Center and Jaggar Museum, were based on the following criteria: a Visitor Center is closed when SO2 concentrations exceed 1 ppm for 6 consecutive 15-minute periods (1.5 hrs), 3 ppm for 3 consecutive 15-minute averages (45 minutes), or 5 ppm for one 15-minute average. NPS high-resolution SO2 analyzers located at the visitor centers operated in the extended 0-10 ppm range.

Flank deformation. The variable-rate inflation of Kilauea that has been ongoing since 2010 continued through 2013. There were periods of slight deflation in March-May, late May, July-August, and September and November. The saw-tooth pattern created by the alternating inflation and deflation is most obvious in the distance change across the Halema'uma'u crater, but can also be seen in the tilt record at summit tiltmeters, such as at station UWE and subtly in the vertical changes at summit GPS sites (figure 226).

Figure 226. (A) Radial tilt measured by borehole instruments at the summit (UWE) and at Pu'u 'O'o (POC) in 2013. Positive change indicating tilt away from the most common magmatic sources, usually indicating inflation, and negative change indicating tilt towards those sources, usually indicating deflation. (B) Changes in distance across Halema'uma'u (UWEV-CRIM) and elevation of GPS stations (HOVL V and OUTL V) from July 2012 through July 2013. Courtesy of HVO.

During 2013, there was a total of almost 10 cm of extension on the approximately 3.5-km baseline between UWEV and CRIM (figure 226 B) and about 10 microradians of inflationary tilt at UWE (figure 226 A). There was very little accumulated vertical change at the summit GPS sites over the year, however. This was also reflected in the lack of appreciable line-of-sight displacement in the interferograms from INSAR spanning 2013. There were 65 deflation-inflation (DI) events in 2013, similar to the rate of occurrence observed since the opening of the summit vent in 2008. Most of these were only weakly detected by the POC tiltmeter at Pu'u 'O'o.

At Pu'u 'O'o, the GPS site on the N rim (PUOC), recorded a fairly steady, slow rate of N-NW motion in 2013, with a slight acceleration in late April-early May. The direction of motion is usually indicative of inflation, but there was no appreciable uplift at the site. There was a net tilt of about 20 microradians to the NW at POC on the N flank, also usually indicative of inflation.

The pattern and velocity of GPS sites on the S flank of Kilauea in 2013 were similar to the patterns and rates that have been observed in the recent past during times free of slow-slip events and ERZ intrusions.

Deformation monitoring equipment. Two continuous GPS sites (LEIA and SPIL) were lost to lava flows from Pu'u 'O'o in early 2013. After a data outage at the Malama Ki (MKI) tilt site on the lower ERZ in April, HVO discovered that thieves had dismantled the gate to the security enclosure and stolen everything except the actual tiltmeter. This had been part of a string of thefts at this site, forcing HVO to eventually abandon it. This was an unfortunate loss to the monitoring network, especially because the only other tiltmeter station on the lower ERZ, near Heiheiahulu (HEI) had also been stolen late during the previous year. In July, HVO installed a new tiltmeter in a less accessible location a few kilometers NW of Heiheiahulu.

Seismicity. In 2013, HVO's seismic network consisted of 57 real-time continuous stations (25 broadband, 21 strong-motion, 7 three-component short-period, and 25 vertical-component short-period instruments) (figure 227). The network coverage was most dense on and around Kilauea. In 2013, HVO upgraded of the seismic network which involved installing the digital stations NAHU (to replace the analog station ESR) and TOUO (to replace analog station KII). They also established three arrays of infrasound sensors in order to better track acoustical waves in the air (infrasound) associated with volcanic processes.

Figure 227. (top) Authoritative region of HVO (black line). Red triangles represent permanent, continuous seismic stations and Netquakes instruments, a new type of digital seismograph that transmits data to USGS via the internet after an earthquake. Stations from the National Strong-Motion Program (NSMP) are excluded here because their high triggering threshold means that they produce data for only a handful of earthquakes a year. (bottom) Map showing both HVO stations (red triangles) and Netquakes (blue triangles). Two boxes indicate regions of special interest for seismic monitoring. Netquakes instruments enable the USGS to achieve a "denser and more uniform spacing of seismographs in select urban areas. … The instruments are designed to be installed in private homes, businesses, public buildings and schools" (USGS, 2013a). Courtesy of HVO.

Seismic activity at Kilauea was generally low in 2013 compared to that of other time periods since the 2008 start of the summit eruption (figure 228). Tremor was a ubiquitous feature of the seismicity near the summit, with discrete very-long-period (VLP) and long-period (LP) events occurring sporadically. Tremor amplitudes appeared to modulate in conjunction with the presence or absence of spattering in the lava lake within Halema'uma'u. In general, increased seismicity in the S caldera and upper ERZ were coincident with rapid increased lava lake level and tilt. None of these swarms were remarkable in number or size compared to previous swarms, especially those in 2011 and 2012.

Figure 228. (A) January-December 2013 earthquake locations, Hawai'i Island, 0-60 km deep, M ≥ 3.0. Earthquake colors are based on depth. The symbol size of the earthquake is based on the preferred magnitude. All plotted earthquakes have been reviewed by an analyst. (B) January-December 2013 earthquake locations, Hawai'i Island, 0-5.0 km deep (shallow), M ≥ 2.0. Earthquake colors are based on time. Symbol sizes are based on the magnitude. Plotted events include both reviewed and automatically determined locations that have horizontal errors < 2 km and vertical errors < 4 km. Courtesy of HVO.

New interactive earthquake webpage launched. In October 2013, HVO launched a new interactive earthquake webpage, informally called Volcweb (USGS, 2013b). The new website used several new technologies that provided a better user-experience and a better compatibility with mobile devices. In addition to providing earthquake location information, the site also creates cross-sections, time-depth plots, cumulative number of earthquake plots, and cumulative magnitude plots for data up to a year old. Webicorders for all stations were available (updated every 10 minutes). The rollout of this website allowed HVO to retire the old "Recent Earthquakes" page.

References. Patrick, M., Orr, T., Sutton, A.J., Elias, T., and Swanson, D., 2013, The first five years of Kilauea's summit eruption in Halema'uma'u crater, 2008-2013. Hawai`i National Park, HI: U.S. Geological Survey, Hawaiian Volcano Observatory, Fact Sheet 2013-3116.

Patrick, M.R., Orr, T., Antolik, L., Lee, L., and Kamibayashi, K., 2014, Continuous monitoring of Hawaiian volcanoes with thermal cameras, Journal of Applied Volcanology, 3:1.

Roeder, P.L., Thornber, C., Poustovetov, A., and Grant, A., 2003, Morphology and composition of spinel in Pu'u 'O'o lava (1996-1998), Kilauea volcano, Hawaii. Journal of Volcanology and Geothermal Research, 123, 245-265.

USGS, 2013a (January). Earthquake Hazards Program, Netquakes: Map of Instruments. Retrieved from http://earthquake.usgs.gov/monitoring/netquakes/map/.

USGS, 2013b (December). Hawaiian Volcano Observatory, Recent Earthquakes in Hawaii. Retrieved from http://hvo.wr.usgs.gov/earthquakes/new.

Geologic Background. Kilauea volcano, which overlaps the east flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions of Kilauea are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai`i National Park, HI 96718, USA (URL: http://hvo.wr.usgs.gov/, Daily updates, http://hvo.wr.usgs.gov/activity/Kilaueastatus.php, and Weekly updates, http://hvo.wr.usgs.gov/volcanowatch/); Hawai`i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai`i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://hotspot.higp.hawaii.edu/); Hawaii 24/7 (URL: http://www.hawaii247.com); Great ShakeOut (URL: http://shakeout.org/hawaii/); and West Hawaii Today (URL: www.westhawaiitoday.com).

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13.37°N, 41.7°E; summit elev. 2218 m

All times are local

Thermal alerts ended mid-2012; revised 2011 plume heights; uplift mechanisms debated

This report shows satellite thermal alerts from the MODVOLC system showing that they continued for 7 months after the end of coverage in our one report on Nabro's June 2011 eruption (BGVN 36:09), with the last alert occurring on 3 June 2012.

What has emerged regarding the 2011 Nabro eruption since our one previous report is a much more detailed eruptive timeline and some substantially taller plume-height estimates. These new and more carefully assessed details came out in at least eight papers and three technical comments (see References below).

The initial Toulouse Volcanic Ash Advisory Center estimates cited in BGVN 36:09 were made in the time-limited operational setting that identifies volcanic ash for aviation safety. Those altitude estimates, which included maximum plume heights on 13 June 2011 in the range of 9.1-13.7 km altitude, have since been reassessed using an array of satellite and ground-based instruments and processing strategies. The revised heights in the subsequent papers often determined plume altitudes above the 16-18 km tropopause and into the stratosphere. Absent in our earlier report but well documented in the papers was evidence of a 16 June 2011 eruptive pulse.

Overall, Nabro erupted a total SO2 mass of at ~1.5 Tg (Clarisse and others, 2012), making the eruption the largest SO2 emitter of the 2002-2012 interval (Bourassa and others, 2013). The various papers and the technical comments have also framed debate on how and when Nabro's plume entered stratosphere.

Thermal alerts. This report does not contain any new in situ observations at Nabro. Table 1 shows MODVOLC thermal alerts during November 2011 and into 2012 on the basis of the number of days with alerts in these months. Those alerts stem from observations made with the MODIS instrument that flies on the Terra and Aqua satellites. Our previous report discussed alerts as late as 5 November 2011, but additional alerts were issued later in the month. For this table, January 2012 was the month with the largest number of days with alerts, 15 days. As of late 2014, the last posted alert was issued on 3 June 2012.

Table 1. MODVOLC thermal alerts recorded for Nabro from November 2012 through September 2014. Courtesy of MODVOLC.

Month Number of days with alerts
November 2011 11
December 2011 08
January 2012 15
February 2012 12
March 2012 07
April 2012 11
May 2012 11
June 2012 01

Although the earlier alerts may signify ongoing eruption, some of the later alerts could stem from ongoing post-eruptive thermal radiance from potentially thick lava flows. Absence of alerts could be the result of clouds masking the volcano, although that is unlikely significant in the terminal alert registered in June 2012. It also bears noting that the alerts are at a fairly high threshold.

References. Bourassa, AE, Robock, A, Randel, WJ, Deshler, T, Rieger, LA, Lloyd, ND, Llewellyn, EJ, and Degenstein, DA, 2012, Large Volcanic Aerosol Load in the Stratosphere Linked to Asian Monsoon Transport. Science 337 (6090):78-81. DOI: 10.1126/science.1219371.

Bourassa, AE, Robock, A, Randel, WJ, Deshler, T, Rieger, LA, Lloyd, ND, Llewellyn, EJ, and Degenstein, DA, 2013, Response to Comments on "Large volcanic aerosol load in the stratosphere linked to Asian Monsoon transport. Science, 339 (6120), 647, DOI: 10.1126/science.1227961.

Clarisse, L., P.-F. Coheur, N. Theys, D. Hurtmans, and C. Clerbaux, 2014, The 2011 Nabro eruption, a SO2 plume height analysis using IASI measurements, Atmos. Chem. Phys., 14, 3095-3111,DOI:10.5194/acp-14-3095-2014.

Clarisse, L., Hurtmans, D., Clerbaux, C., Hadji-Lazaro, J., Ngadi, Y., & Coheur, P. F., 2012, Retrieval of sulphur dioxide from the infrared atmospheric sounding interferometer (IASI). Atmospheric Measurement Techniques Discussions, 4, 7241-7275 [13 March 2012; revised from 2011 version] www.atmos-meas-tech.net/5/581/2012/; DOI:10.5194/amt-5-581-2012.

Fairlie, T. D., Vernier, J.-P., Natarajan, M., and Bedka, K. M., 2014, Dispersion of the Nabro volcanic plume and its relation to the Asian summer monsoon, Atmos. Chem. Phys., 14, 7045-7057, DOI:10.5194/acp-14-7045-2014, 2014.

Fromm, M, Nedoluha, G, and Charvat, Z, 2013, Comment on "Large Volcanic Aerosol Load in the Stratosphere Linked to Asian Monsoon Transport." Science 339 (6120). DOI: 10.1126/science.1228605.

Fromm, M, Kablick, G (III), Nedoluha1, G., Carboni, E., Grainger, R., Campbell, J, and Lewis, J., 2014, Correcting the record of volcanic stratospheric aerosol impact: Nabro and Sarychev Peak, Journal of Geophysical Research. Atmospheres. [Early, online version, accessed August 2014] DOI: 10.1002/2014JD021507

Pan, LL, and Munchak, LA, 2011, Relationship of cloud top to the tropopause and jet structure from CALIPSO data. Journal of Geophysical Research: Atmospheres (1984-2012) 116.D12 (2011).

Penning de Vries, M. J. M., Dörner, S., Pukite, J., Hörmann, C., Fromm, M. D., & Wagner, T. (2014). Characterisation of a stratospheric sulfate plume from the Nabro volcano using a combination of passive satellite measurements in nadir and limb geometry. Atmospheric Chemistry and Physics, 14(15), 8149-8163.

Theys, N., Campion, R., Clarisse, L., Brenot, H., van Gent, J., Dils, B., Corradini, S., Merucci, L., Coheur, P.-F., Van Roozendael, M., Hurtmans, D., Clerbaux, C., Tait, S., and Ferrucci, F.: Volcanic SO2 fluxes derived from satellite data: a survey using OMI, GOME-2, IASI and MODIS, Atmos. Chem. Phys., 13, 5945-5968, doi:10.5194/acp-13-5945-2013, 2013.

Vernier, JP, Thomason, LW, Fairlie, TD, Minnis, P., Palikonda, R, and Bedka, K M, 2013. Comment on "Large Volcanic Aerosol Load in the Stratosphere Linked to Asian Monsoon Transport." Science 339 (6120). DOI: 10.1126/science.1227817.

Geologic Background. The 2218-m-high Nabro stratovolcano is the highest volcano in the Danakil depression of northern Ethiopia and Eritrea. Located at the SE end of the Danakil Alps, Nabro lies in the Danakil horst. Nabro is the most prominent and NE-most of three volcanoes with large summit calderas aligned in a NE-SW direction SW of Dubbi volcano. These three volcanoes, along with Sork Ale volcano, collectively comprise the Bidu volcanic complex. The complex Nabro stratovolcano is truncated by nested calderas, 8 and 5 km in diameter. The larger caldera is widely breached to the SW. Nabro was constructed primarily of trachytic lava flows and pyroclastics. Post-caldera rhyolitic obsidian domes and basaltic lava flows were erupted inside the caldera and on its flanks. Some very recent lava flows were erupted from NNW-trending fissures transverse to the trend of the Nabro volcanic range.

Information Contacts: Hawai'i Institute of Geophysics and Planetology (HIGP) MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI (URL: http://hotspot.higp.hawaii.edu/); and Toulouse Volcanic Ash Advisory Centre (VAAC) (URL: http://www.ssd.noaa.gov/VAAC/OTH/FR/messages.html).

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14.381°N, 90.601°W; summit elev. 2552 m

All times are local

Sudden, bomb-laden explosions of 27-28 May 2010; extra-crater lava flows

Introduction. Pacaya, which in recent years has consistently erupted olivine-bearing high alumina basaltic lavas, erupted with remarkable violence on both 27 and 28 May 2010 with an explosion on the 27th lasting ~45 minutes. This was followed by a smaller explosion the next day that generated a plume assessed from satellite and meteorological data as reaching 13 km altitude. In this report we describe those events as explosions in order to distinguish them from the ongoing, decades-long, and often effusive eruption generally seen at Pacaya. The terms ‘explosion’ and ‘explosive’ appear warranted given such factors as the suddenness of escalation, the ~13 km plume altitude (~10 km over the summit when measured during the weaker explosion on the 28th, the density of projectiles, and the scale of the tephra fall. The term explosion seems consistent with common practice (Sparks, 1986; Fiske and others, 2009).

The following report emphasizes Pacaya’s behavior in 2010, including the 27 and 28 May explosions and impacts continuing into early June 2010. Our last report (BGVN 34:12) discussed behavior into mid-January 2010. Some of the reporting came from reports of Guatemalan agencies (eg. INSIVUMEH and CONRED, acronyms spelled out in the Information contacts section at bottom), newspapers (eg. Prense Libra, 2010a, b), videos and photos, and cited manuscripts and papers. It especially benefited from a draft manuscript prepared by Rüdiger Escobar Wolf (REW, 2014) and graciously provided to Bulletin editors. REW also provided reviews, insights, and numerous tailored graphics but bears no responsibility for possible errors induced by Bulletin editors.

The explosions were preceded months to weeks earlier by extra-crater venting of lava flows on the E and SE flanks. The lava flows covered substantial areas after emerging effusively at two widely spaced vents in atypical extra-crater or crater-margin locations.

Following the Introduction, this report’s subsections address the following topics: (1) the Guatemalan hazard agency CONRED’s reports, (2) a sample of available video and photo documentation of Pacaya’s behavior, (3) events prior to the 27 May explosion, (4) the explosions and some of the impacts, (5) the seismic record showing the pattern of escalation around the time of the explosions, (6) a brief summary of the critical initial aviation reports, and (7) a geotechnical slope stability study that suggests gravitational instability at Pacaya, particularly owing to the cone’s magma pressure and seismic loading.

Pacaya , which has a record of eruptions dating back over 1,600 years, has been erupting the majority of the time since 1961, often emitting rough-surfaced lavas but also occasionally discharging explosions. The centerpiece of the National Park of the same name, it is the most often climbed volcano in Guatemala. There have been 69 prior Smithsonian-published reports describing behavior from 1969 to early January 2010 (CSLP 03-70 to BGVN 34:12). REW (2013) ranked the 27 May explosions as sub-plinean and the associated lava emissions as the largest since similar events in 1961.

Figure 42 shows two simplified regional maps of Guatemala and neighboring countries including Mexico, Belize, Honduras, and El Salvador.

Figure 42. (Top) A map showing Pacaya’s location in Central America. (Bottom) A map emphasizing Pacaya’s location with respect to the central portion of Guatemala City (red square labeled ‘Guatemala’). The larger combined urban area associated with that Capital city stretches well beyond the square symbol and contains ~3.5 million residents. AmatitlÁn was heavily damaged by Pacaya’s May 2010 ashfall and the knock-on effects of Tropical Storm Agnes that arrived two days later. Top map taken from Morgan and others (2012); bottom map revised from a base map found online at Ezilon Maps.

The larger tephra blanket spread N, covering an area of more than 1,000 km2 including the bulk of the Guatemala City metropolitan area, the largest city in Central America, population ~3.5 million. The City’s center lies ~25 km NNE of Pacaya’s summit but a 5-km-wide strip of urban and suburban development now stretches from its older core (red square, figure 42)to ~9 km N of the summit. The tephra shut down La Aurora, the county’s primary international airport and among the region’s busiest, for 5 consecutive days.

The 27 May 2010 explosion destroyed or damaged nearly 800 houses in nearby communities, forcing ~2,000 residents to evacuate and injuring 59 people. A high density of ballistics fell on nearby hamlets and villages, particularly those 2.5-3.5 km N of the MacKenny cone (El Cedro, San Francisco de Sales, and Calderas). The ballistics had sufficient mass and velocity to puncture roofs with a density on the order of one puncture per square meter in some places. Many more smaller ballistics bent but did not penetrate the corrugated sheet metal roofs common in many of the region's dwellings. Some of the ballistics were sufficiently hot to start fires.

Ash caused widespread damage locally, and up to ~8 cm of ash fell on parts of metropolitan Guatemala City, the nation’s capital, centered ~35 km NNW of Pacaya. Up to 20 cm of tephra accumulated at and near Pacaya. According to available census data, the population within 10 km of Pacaya was 57,000 (John Ewert, USGS-CVO, personal communication).

Accounts from Guatemalan meteorological stations reported that detectable ash from the 2010 explosions fell as far away as the Caribbean coast. Brianna Hetland was both a graduate student in volcanology and a US Peace Corps Volunteer in Guatemala during 2010-2012. Hetland noted in a message that she had spoken with another Volunteer who said ash had blanketed his neighborhood near Coban (in Samac, Alta Verapaz) ~180 m N of Pacaya (figure 42, bottom). Hetland documented post-eruptive conditions at Pacaya, composed a blog on the impact and clean up, and gave a talk on those aspects as well as multifaceted monitoring conducted by fellow students and faculty at Michigan Technological University (Hetland, 2012a, b; Walikainen, 2010).

Some of the impacts of the freshly fallen ash were amplified and other impacts were diminished by heavy rains and flooding due to Tropical Storm Agatha that struck the region 2 days later, with some areas receiving 0.9 m of rain. The floodwater run carried ash that dislodged debris, clogged drainage systems, left thick deposits on valley floors, and damaged many bridges. The scale of the combined disasters led to more analysis of hardships, mitigation, and economic impact than usual at many eruptions, as exemplified by the detailed assessments by Wardman and others (2012). Those authors visited in the aftermath from New Zealand in order to study impacts that might be analogous to hazards elsewhere. They found that one moderating impact of the rain was to cee crops, which were washed clean of ash and residual acids. The authors also found that that a prompt and efficient cleanup was initiated by the Capital municipality to remove tephra from the 2,100 km of roads in the Capital. An estimated 11,350,000 m3 of tephra was removed from the city’s roads and rooftops.

Diminishing strombolian activity and lava flows in the crater area continued into at least late June 2010. By this time the emissions had become more like the generally effusive decades-long eruption, which was still ongoing when this was written in late 2014. In addition to the information here, Pacaya’s discharge rates have been summarized for the years 2004-2010 on the basis of infrared satellite images (Morgan and others, 2013). As would be expected, a strong peak in radiance developed in late May 2010.

REW (2013) noted one death attributed to the explosion and tephra fall and 179 deaths attributed to the Tropical Storm. Two people died at Pacaya days prior to the explosion of 27 May 2010. Wardman and others (2013) mentioned two further deaths due to people cleaning tephra from roofs.

Geochemical analysis of material erupted on 27 and 28 May is not yet reported. As background, Matías and others (2012) describe Pacaya’s recent lavas as all high-alumina basalts with SiO2 contents of 50-52.5 weight percent and MgO contents of 3-5 weight percent. Common phynocrysts (visible minerals) included plagioclase, olivine, and opaque minerals (Conway, 1995). There is a slight variation of CaO in this group of lavas, which suggests a phenocryst enrichment or depletion. The lava compositions have remained broadly similar since 1961, and for many previous lavas as well, although some more felsic compositions are represented at older flank eruptions (Eggers, 1971).

CONRED reports. Perspective on the disaster can be gained from the chronology and content of announcements issued by CONRED (the Guatemalan agency for disaster reduction; Coordinadora Nacional para la Reducción de Desastres, table 4). These will be referred to in text by “CONRED” followed by their bulletin number.

Table 4. A summary of key CONRED information bulletins issued relevant to Pacaya’s May 2010 eruption (http://conred.gob.gt/). After Escobar Wolf (2012) in addition to a similar table by Wardman and others (2012). Not all bulletins are included in this table.

Date CONRED Bulletin Summary

10 Feb 2010


Called attention to lavas emitted on the E to S flanks.

17 May 2010


Recommended the National Park restrict access to the lava flows.

26 May 2010


Eruptive activity increased during the day, generating plumes of 1 km above the vent that dispersed fine tephra onto neighboring villages. Recommended closing access to Park. Warned air traffic authorities about risks to aviation.

27 May 2010


Began to mobilize staff to villages near volcano around 1500 on the 27th, to discuss and implement pre-emptive evacuation. Seven shelters were prepared in San Vicente Pacaya to accommodate refugees.

When the paroxysmal phase of eruption started (after 1900), evacuation of villages to the W (El Rodeo and El Patrocinio) was already underway, however, tephra and ballistics were dispersed primarily to the N and the villages of El Cedro, San Francisco de Sales and Calderas were the most severely affected.


28 May 2010




Declared Red Alert. As of 1239 on the 28th over 1600 people had been evacuated from the villages of San Francisco de Sales, El Rodeo, El Patrocinio, El Cedro, Calderas, and Caracolito. They moved to San Vicente Pacaya.

Civil Aviation authorities closed La Aurora International Airport due to tephra fall. The Ministry of Education closed schools in Escuintla, Sacatepequez and Guatemala departments. Access to the National Park remained restricted.

The municipality-level response agency (with a similar name, COMRED, not CONRED) was activated in Villa Canales. It set up shelters in the municipal auditorium, a church, and the municipal hall.

Advised citizens on managing the tephra fall.


28 May 2010


Thus far the eruption had injured 59 people, killed 1, and prompted the evacuation of nearly 2000.


8 May 2010




In the afternoon at 1424 on the 28th, high eruptive vigor resumed and tephra again fell on Guatemala City, but in much smaller quantities than during the previous day.


29 May 2010


By this time, a total of 2635 people were in shelters due to the eruption; ~400 houses had been slightly damaged and 375, severely damaged.

27 May 2011


One year later; a retrospective summary of civil defense responses to the eruption and the larger engulfing disaster, tropical storm Agatha.

Events prior to the energetic 27 May explosion. Figure 43 highlights Pacaya’s vent locations (1961 to 2009 vents as green dots), including the two new E and SE flank vents that emitted lava flows (red areas).

Figure 43. Simplified geological map of Pacaya, based on cited references, INSIVUMEH mapping, and GOES satellite data. The key at right calls attention to features such as the collapse scarp forming the N and E of margin of the main crater and the lava flows of prehistoric age (Eggers, 1969, 1972; Bonis, 1993) through about mid-2010. Migrating vents mapped during 1961-2012 (Matías, 2010; Rose and others, 2012) appear as dark-green dots (many clustered on or near the MacKenney cone’s summit). The red areas on the SE flank and E flank represent lava with the noted age constraints from REW’s analysis of satellite data. The SE flank vent had emitted by mid-2010 a field of lava approaching the size of the 1961 Cachiajinas lava flow (purple). The latter flow both vented and advanced within Pacaya’s collapse scarp. In contrast, the SE flank flow was the first in historical times to vent and flow outboard of the scarp. The cone residing on Pacaya’s NW rim, Cerro Chino, enters discussion frequently in this report. Note the depression (notch or trough) here labeled “New fissure like structure.” Map created and provided by REW.

Changes in eruption behavior preceded the 27-28 May explosions by several months.

From 2004 to around the end of 2009, Pacaya’s eruptive intensity was often low. A clear sign of changes took place in February 2010 when lava flows emerged at vents on the S and SE flanks (table 1). These vents sit well outboard of the usual points of lava emission, which have in recent decades been limited to spots within the central crater, an area bounded by a large engulfing collapse scarp (a Somma rim; Eggers, 1969; figure 43). The two previously mentioned deaths occurred on 18 April when, according to the news, they were hit by a rock avalanched caused by an explosion. By 17 May, SE flank lava flows had reached 1.5 km long and the Park began restricting access (table 1).

The scene on the SE flank appears in figure 44.

Figure 44. Pacaya’s SE flank eruption as seen during the day on 27 May 2010. The ultimate distribution of lavas appears on the preliminary map by REW (2014). Image courtesy of Gustavo Chigna (INSIVUMEH).

Earlier on the 27th (prior to the explosion), INSIVUMEH volcanologist Gustavo Chigna looked out over the crater area and counted at least 16 distinct vents emitting lava. Chigna was surprised, and his’s comment was something like, ‘It looked like water gushing out of a sieve.’ That scale of new extrusive sites helped alert authorities that the volcano’s behavior had escalated well beyond the norm and led to restricting public access to Pacaya.

During the 5 years prior to the 27 May 2010 explosion, sporadic vent openings limited to the MacKenney cone and adjacent areas (particularly the N crater) extruded lava flows (green dots, figure 43). Many of the resulting lava flows were each only active for periods of days to months. INSIVUMEH sometimes reported multiple simultaneous lava flows from distinct vents on the cone, which occurred, for example, during April 2009. Most of the lava was confined to the main crater or portions downslope and W of the E-bounding collapse scarp. The case in 2005 illustrated that the topographic boundary associated with the NE segment of the collapse scarp had diminished in places to the point where lava flows could cross the scarp (BGVN 33:08).

Around January 2010, Gustavo Chigna (INSIVUMEH) indicted the end of mainly lower effusive activity ongoing since 2004. The new upsurge fed several lava flows from vents on Pacaya’s main cone. In harmony with this comment, the video by Crossman (2009) indicates that on 24 December 2009 the volcano emitted considerable lava. Venting was effusive and at both the MacKenney cone’s summit and base. Visible plumes were nearly absent.

Table 5 lists a small sample of available videos taken at Pacaya that aid in documenting its behavior. The table includes videos taken before, during, or shortly after the 27 May explosion, with the two pre-explosion videos capturing behavior relevant to this subsection. The videos from other parts of the table are discussed in appropriate sections below.

Table 5. Some photos and videos that advance understanding of Pacaya behavior during December 2009 to about 2 June 2010 (a week after the explosion). The cases presented are a sample, not an exhaustive list. Compiled by Bulletin editors.

Video (V) or Photo (P) and source Date acquired / Date posted if clearly stated)

Title; Content; URL

How cited in text of this report

V; Patrick R. Crossman

24 Dec 2009 / 24 Dec 2011

Title: “Hiking the Pacaya volcano in Guatemala”

This video chronicles a group visiting Pacaya amid ongoing effusive volcanism in comparatively calm conditions and with people in many scenes. Some parts of the video depict a narrow (1- to 2-m wide), channelized, slowly moving lava flow.  That flow appears to vent near the base of the MacKenney cone, devoid of visible plume, and traverses a region of low incline.  The path of the molten flow is sinuous rather than linear.  The visitors roast marshmallows in radiant heat from the flows.  The video also cuts to scenes at the MacKenney cone’s summit, where a larger flow several meters wide vents in a stable, effusive manner, also devoid of an associated plume.


Cited in text as Crossman, 2011

V & P;

H. Paul Moon (Zen Violence Films, LLC)

1 April 2010 / 24 April

[Date confirmed with Moon and by comparison to his dated still photos]

Title: “Pacaya Volcano, Guatemala [1080p HD]”

Close up views showing copious lava flowing down the E flank from the new vent there.  Accompanies GPS record of hiking track and still photos.   Music accompanies the video.  Dovetails with a Landsat image from about a week earlier, which also documents the E flank lavas.  See text for more discussion.



Associated link shows GPS path on a satellite image

Cited in text as Moon, 2010


RT news channel (original authorship not provided)

-- / 28 May 2010

Title: “Video of Guatemala Pacaya volcano eruption”

Compact, powerful strombolian explosions throwing molten ejecta vertically from multiple vents, or an elongate vent such as a fissure in Pacaya’s crater (see photo below in figure 52).


Cited in text as RT News, 2010a


RT news channel (original authorship not provided)

 --/ 30 May 2010

Title: “Raw video of damage caused by volcano eruptions in Guatemala and Ecuador”;

The video shows, for Pacaya, images of advancing lava flows and some distant views of the volcano in daylight with a moderate plume above it.   There are many scenes of damage, evacuation, and human impact, including ash-loaded corrugated metal roofs that buckled; ash on airliners; brigades of people sweeping and carting off ash from city streets and an airport runway; and children sheltering in a relief center. 



Cited in text as RT News, 2010b



27-31 May / 2 June 2010

Title: “A Rough Week for Guatemala” (in The Big Picture—News Stories in Photographs)

       “In just the past seven days, residents of Guatemala and parts of neighboring Honduras and El Salvador have had to cope with a volcanic eruption and ash fall, a powerful tropical storm, the resulting floods and landslides, and a frightening sinkhole in Guatemala City that swallowed up a small building and an intersection. Pacaya volcano started erupting lava and rocks on May 27th, blanketing Guatemala City with ash, closing the airport, and killing one television reporter who was near the eruption. Two days later, as Guatemalans worked to clear the ash, Tropical Storm Agatha made landfall bringing heavy rains that washed away bridges, filled some villages with mud, and somehow triggered the giant sinkhole--the exact cause is still being studied. (34 photos total).”

(URL: http://www.boston.com/bigpicture/2010/06/a_rough_week_for_guatemala.html)

Cited in text as Boston.com, 2010

V; Tropical-rambler (clear authorship not provided)

31 May 2010 / 31 May 2010

Title: “Erupción Volcán de Pacaya - Pacaya volcano Eruption”

Helicopter views of flight generally towards, and then at, Pacaya, which was still in eruption, with initial views showing Agua volcano and parts of Lake Amatitlán.  Low weather clouds covered extensive areas.  This video captured a decidedly non-vertical, denser black plume from Pacaya feeding a lighter, tan colored more massive plume that appears to drop ash as it  is carried to ten’s of kilometers downwind (directed E-SE-S).   Shots include those of Cerro Chino and antenna towers there, and widespread steaming on the MacKenney cone that coalesced into large steam clouds low over much of the central crater area.


Cited in text as Author unknown, 2010

V; Prensa Libre.com (wwprensalibrecom)

About 2-3 June 2010/ 10 June 2010

Title: “Espectacular erupción en el Pacaya”

(Narration by news reporter referring to explosion as 1 week ago, thus the ‘About 2 -3 June’ date in the previous column.)  According to REW , this video shows lavas emitted at the new SE flank vent.   Remarkable images, some seemingly shot from helicopter and others from the ground, showing copious channelized lava flows moving rapidly downslope to the SE.  At the vent area there are three small vents discharging spatter from coalescing cones with very steep sides.  Their glowing summit craters gave off occasional eruptions as well as occasional puffs of gases, glowing spatter, and possibly flames.  Some shots show incandescent lava flows several kilometers long. Rising plumes sometimes display toroidal motion, rotational behavior reminiscent of dust devils.


Cited in text as Prensa Libre, 2010

Figure 45 shows one of several Landsat views of the E flank in an infrared image acquired on 23 March 2010. It showed high thermal radiance in a narrow linear thermal anomaly headed E outboard of the usual eruptions confined to the crater. The E-flank area is devoid of vegetation, which rules out a local fire there, meaning that the anomaly was due to a lava flow. The number of clear (cloud-free) views of Pacaya available during March through June was limited. REW plotted this anomaly in a KMZ file format (red line, figure 46).

Figure 45. A Landsat 7 thermal image of Pacaya on 23 March 2010 showing high heat flux as red. The small red area is on the MacKenney cone. The larger red area is a lava flow that had extended E. A site visit and video by Moon (2010) on 1 April (8 days later) confirmed lava flows on the order of 2-4 m wide. Black and marginal gray areas are older lava flows; green areas are vegetated with some cultivated or pasture land in shades of brown. This image contains artifacts in the form of gray diagonal stripes. The stripes are due to the failure of the Scan Line Corrector (SLC), which compensates for the satellite’s forward motion. Courtesy of REW.
Figure 46. A Google Earth view of the land surface looking radially outward (E) down Pacaya’s E flank (N is to the left). The red line indicates the location of the lava flow axis from heat flux in Landsat images. The flow’s source was at or very near the collapse scarp. The yellow line indicates the film crew’s 1 April 2010 excursion route recorded with GPS as they approached the lava flow, filmed it at close range, and then headed back towards the trailhead (Moon, 2010). For scale, the lava flow is ~0.3 km long. Graphic files, analysis, and compilation created and provided by REW.

The new E flank (extra-crater) lava flow documented by Landsat on 23 March was the subject of a video by Moon (2010) taken on 1 April (table 1; see their excursion route on figure 46). The footage was shot during daylight hours at high resolution [1080p HD] and later processed to obtain vibrant red, orange, and yellow colors.

The discharges were effusive and few visible emission clouds accompanied the lava flows seen in the video. A dark plume remained above the MacKenney cone’s summit.

As seen in fs 47-50, the lava documented by Moon (2010) in photo and video was several meters wide and passing over irregular terrain. As seen from a distance (eg. figure 47), some sectors of the flow’s channel stood well above the surrounding landscape. In the area visited, the lava remained confined behind jumbled but effective levees as it passed through and over the a’a (rough textured) flow field.

Figure 47. A 1 April 2010 photo of Pacaya’s E flank lava flow seen in the distance as it descends across an a’a flow field. Courtesy of H. Paul Moon (see table 5).
Figure 48. Pacaya’s E-flank lava flow on 1 April 2010 upon closer approach than previous f. After watching the video Moon (2010), REW commented that the flow looked like “a typical channel-levee aa flow developed on a steep slope.” Courtesy of H. Paul Moon (see table 5).
Figure 49.. Pacaya’s E-flank lava flow on 1 April 2010 upon closer approach than previous f. For scale, note exposed portion of ~1.4 m long hiking stick in right foreground. Courtesy of H. Paul Moon (see table 5).
Figure 50. A still closer view of Pacaya’s E-flank lava (taken from just a few meters away), which was moving swiftly. In his YouTube notes on his teams 1 April 2010 visit Moon commented that “the heat was so intense that I could only hold out for brief shots, needing to turn away regularly to avoid getting scorched.” Courtesy of H. Paul Moon (see table 5).

Figure 51 maps the inferred E flank lava flow axis and SE flank fissures on an oblique Google Earth view.

Figure 51. An oblique Google Earth view of Pacaya looking roughly WNW. At left in orange appear the upslope areas of the fissures that fed the SE flank lava flows. Farther NE (to the right) appear another set of fresh black lavas that reside on the upper E flank. The green line traces high heat emissions REW found in Landsat imagery from 23 March 2010, the same lava flow that had been the subject of Moon’s video ~8 days later. Both sets of flows and vents were the first clearly documented to extend E of the collapse scarp in historical times. Analysis, compilation, and topographic files all provided by REW.

On 18 April 2010, according to a news report in the newspaper Prensa Libre, a Venezuelan tourist and her Guatemalan guide died on Pacaya. The news report stated the deceased were in the area of high risk when struck by material released from an explosion. Some of the other 14 people on the scene sustained injuries.

On 17 May 2010, observers saw abundant lava escaping from a new SE-flank vent (CONRED 708). A mound had formed at the vent area. The lava from this vent had by 17 May extended as far as 1.5 km. As seen on figure 43, the SE flank lava flows and their fissures ultimately fed lava flows trending roughly S for ~2.5 km then turning sharply (~90 degrees) to the W and extending in that direction another ~2.5 km.

CONRED 708 made a recommendation to the Pacaya National Park authority to restrict visitor access to the lava flows. The 17 May report noted that Pacaya’s activity was considered to be relatively high, but it left out language suggesting a crisis at this point. According to the press, access to the volcano was restricted following the recommendation.

On 17 May, the newspaper Prensa Libre featured an undated night photo of the MacKenney cone taken from the N, presumably of this stage of Pacaya’s eruption. It showed a dense spray of glowing material thrown from the MacKenney cone’s summit and rising hundreds of meters. The cone’s N rim contained a recently formed V-shaped notch (or trough). Out of that notch poured a broad lava flow. Several hundred meters down the MacKenney cone’s N face, the broad flow split into two flows descending the cone’s steep face on diverging paths. The notch in the cone stands out as a clear morphologic change associated with this time interval (~10 days prior to the 27 May explosion), and as will be seen below, it served as a conspicuous vent site for the fissure emissions documented during the explosions.

The day before the explosion, on 26 May, eruptive and seismic intensity both increased markedly. An eruptive plume reached 1 km above the vent and fine tephra fell on villages around the volcano (CONRED 726 on 26 May, table 1). CONRED recommended fully closing Pacaya National Park, and they warned aviation authorities of airborne ash near Pacaya. No call was yet made to evacuate residents living adjacent Pacaya.

Vigorous explosions starting 27 May 2010. Pacaya’s eruptive vigor increased to the point of strong strombolian eruption, with the initial increase noted on the 27th in a morning report in Prensa Libre. More intense explosions occurred at around 1500 when observers noted explosions discharging about once per second and saw glowing material thrown ~1.5 km above the crater, and taller rising dark clouds carrying finer tephra that dispersed over nearby villages.

The exact start time of the intense 27 May explosion is variously reported, but available visual observations suggested to REW (2014) that it was during the interval 1800-1900. CONRED 729 indicated the climax (the explosion)began at 1900. Seismic data, discussed in a subsection below underwent the highest (RSAM) amplitudes during 1730-1830 local time on the 27th. Aviation reporting of satellite data on eruptive plumes, discussed in a subsection below, was initially ineffectual for the 27th owing to above-lying weather clouds.

What is clear is that the explosion late in the day on the 27th drove forth intense fire fountaining and vigorous ejection of tephra and ballistics.

Figure 52 shows a broad fire fountain frame taken from a Youtube video posted on 28 May—but it lacked an acquisition date (RT news channel, 2010a). REW interprets this video as taken during the major climax (explosion) during the night on the 27th. The eruption was clearly of fissure style at this point but the upper extent of the glowing material was possibly masked by ash clouds. Some of the textures within the glowing region are explained in the f caption and in the text below.

Figure 52. A frame captured from a news video taken at night from Pacaya’s NNW side documenting powerful curtain-style emissions (fire fountains) from the main crater area (which includes the MacKenney cone). The foreground consists of the dark silhouette of Cerro Chino (indicated on figure 43). Some of the tall antenna towers there appear as narrow vertical dark streaks backlit by the brighter orange fire fountains. Many of the towers and radio shacks on the ground near their bases were destroyed. Taken from RT news (see table 5 (RT News, 2010 (a)).

REW described the video source for figure 52 as taken looking at Cerro Chino (indicated on figure 43) from at or near the town of El Cedro, ~3 km to the NNW of the vent. The diffuse zones of near darkness in the midst of the fountains are rising ash clouds locally diminishing the glow. Thus it is clear from the dynamics seen on the video, that the glow of higher reaching clasts in the upper portions of this image could possibly be masked by dense ash plumes.

On the video, the orange streaks from glowing airborne pyroclasts track to points below that suggest emission from multiple vents or an elongate vent with continuous extent, rather than a single point source, a topic returned to below in the context of an elongate trough developed on the MacKenney cone. That said, REW points out that it is hard to get a good idea of the scale from this video and that videos taken from other locations seem to show a wider, and at times two different fountain jets. Available video and photographic data has thus far prohibited estimating the width of the fountain at this stage of the eruption. REW (2013) citing Hetland (personal communication) and CONRED 856 noted that associated with these emissions the major tephra fall began, and it soon spread tens of kilometers to the N.

Early in the explosion on the 27th (exact timing unknown), a news team from a national television station (Notisiete) endured a shower of ballistics. REW (2013) noted that they were in the vicinity of Cerro Chino at probably less than 1 km from the vent, the zone with critical infrastructure most impacted (figure 53). Although most of the news team survived, reporter Anibal Archila’s death was apparently the result of direct impact from a large ballistic. His was the only icially confirmed death caused by the strong explosive phase. During a subsequent eruptive lull, a rescue team spent several dangerous hours in very close proximity to the vent, finding and rescuing missing people, and carrying out Archila’s body.

Figure 53. A truck parked directly N of the Pacaya’s active crater at Cerro Chino as seen in the aftermath of the 27-28 May explosions. Courtesy of Gustavo Chigna (INSIVUMEH).

Ballistics in excess of 0.5 m on their long axis fell at Cerro Chino and elsewhere within ~1 km of the vent area (figure 54). Some bombs on the ground reached sizes of 80 x 50 cm (Hetland personal communication) but part of that extent may have been due to splattering on impact. Farther away, the sizes of ballistics generally diminished with distance from the source. At Cerro Chino ballistic impacts broke concrete roofs, started fires in the radio shacks, and toppled antenna towers (REW, 2014; Wardman and others, 2010).

Figure 54. An example of a large bomb found in the near-source region. Courtesy of Gustavo Chigna (INSIVMEH).

When the intense phase started on the 27th, the evacuation of villages to the W (El Rodeo and El Patrocinio) was already underway. During the hours after the explosion’s onset on the 27th, more than 2,100 people were evacuated from the proximal villages to the town of San Vicente Pacaya (5 km NNW)(see related scenes in RT news, 2010 (b), table 1).

The settlements El Cedro, San Francisco de Sales, and Calderas, towns 2.5-3.5 km to the N, endured both ash as well as a dense barrage of hot ballistic bombs (figure 55). Many of the bombs were below 20 cm in diameter. Some of the ballistics pierced the corrugated (sheet metal or fiber cement) roofing common in Latin America. In some cases the ballistics also ignited fires that consumed most of the combustible contents of the buildings. Some roofs collapsed or buckled due to the load of deposited tephra.

Figure 55. Two photos taken soon after Pacaya’s 27-28 May eruptions illustrate the density of projectile penetrations through roofs of two large buildings in San Francisco de Sales (~3 km N of the MacKenney cone). Taken from REW (2013) with photo credit to Hetland.

The ballistics examined were of low density owing to vesicles larger than 1 mm in diameter. They contained sparse phenocrysts (often larger than 1 mm), most likely plagioclase (Hetland personal communication to REW and Hetland (2010).

REW (2013) noted that, from the observed damage to roofs in these villages, the density per unit area of impacts that pierced through the corrugated roofs averaged as high as on the order of 1 per square meter. Portions of the roofs in near-vent settlements also sustained many dents from bombs that delivered impacts with lower force. Although some communities were partially evacuated when many of the ballistics arrived, REW (2013) concluded that some residents remained within the communities and regions mostly affected.

Reports in Prensa Libre give insights into the scene of the evacuation and the barrage. Many of the residents evacuated on foot following narrow paths across the rugged rural terrain. Other residents remained behind in order to protect their belongings from theft. When the barrage came, those too close used whatever hard and resistant objects they could find to protect themselves, including hiding under furniture and using pots and pans to protect their heads. Some corroded metal roofs were weak prior to the eruption. Some people found refuge in buildings with heavier, concrete-slab roofs, which generally fared better.

Figure 56 shows an individual who clearly received medical attention, stitches, for a laceration on his forehead. According to REW (2013), Pacaya’s 2010 ballistic barrage caused more injuries than any recent eruptions. That said, data remain scanty on injuries rates and kinds, resultant disabilities, accident location, etc., although Wardman and others (2012) compiled some statistics.

Figure 56. Ballistic projectiles presented the most direct hazard from the 2010 explosions at Pacaya. This photo was found on the Boston Globe photo news site Boston.com (table 5). Their caption read, “A man shows the stitches he received after being injured by volcanic rock on the slopes of the Pacaya Volcano on May 28, 2010. (REUTERS/Daniel LeClair).” Courtesy of Boston.com.

The AmatitlÁn geothermal plant, located ~3 km N of the MacKenney cone to the N of San Francisco de Sales received ~20 cm of mostly lapilli-sized tephra. As Wardman and others (2012) noted, “Ballistic bombs and blocks also bombarded the plant, causing extensive damage to the plant’s roof and condenser fans. Fan blades were dented, bent and also suffered damage from abrasion. Minor denting of the intake and outlet pipe cladding was also reported however these impacts were superficial and did not require repair.” A photo showed cladding bearing multiple closely spaced dents on the side of a large pipe; the largest dent, 20 cm across, had ruptured through the sheet metal.

Post-explosion assessment of the MacKenney cone shed new light on the form and significance of the previously mentioned notch across it (a linear NW-trending trough passing through the summit, figure 57).

Figure 57. An annotated photo viewing the N side of the MacKenney cone in calm conditions at an unstated date following the May 2010 explosions. The prominent trough included a deep segment that had developed on the cone’s lower slopes (labeled ‘Possible crater’). During the 27-28 May 2010 eruption the trough appears to have served as an active fissure or series of vents emitting fountains (see figure 52 and related discussion). Courtesy of REW with photo credit to Gustavo Chigna.

The notch formed a prominent depression aligned both with the new SE-flank fissures and Cerro Chino cone on the outer NW crater rim. Portions of the RT video footage taken during vigorous stages of explosion suggests that at a paroxysmal stage of the explosion the trough served as an eruptive fissure emitting a vertically directed fountain as a curtain (table 5). REW (2013) also suggested that the eruptive fissure along the trough may have served as the vent for the ballistics that fell in previously mentioned settlements to the N.

The explosions broadest areal impact came from tephra fall. Figure 58 shows a close up of ash from a sample collected 22 km from the vent. Overall, the grain sizes ranged from sub-millimeter to centimeter size. An abundance of fine suspended particles in the air were not reported during or following the tephra fall.

Figure 58. Close up view looking at Pacaya tephra clasts collected in Guatemala City ~22 km NNE of the source. The smallest increments on ruler are in millimeters; the size range of grains here were mostly below ~ 3 mm diameter but grains under 0.2 mm were scarce to absent. The clasts consisted of black to dark brown vitric (crystal poor) scoria. Taken from REW (2013), who cited R. Cabria (personal communication).

As noted in table 1, in the afternoon on the 28th, high eruptive vigor resumed and tephra again fell on Guatemala City (CONRED 735). The ash fall on this day was lighter than on the 27th. Here aviation data (discussed below) did record the plume via satellite. The Washington Volcanic Ash Advisory Center (VAAC) noted (in their 6th advisory) an eruption in the afternoon on the 28th reaching (based on comparison of plume movement to modeling of winds aloft) ~13 km altitude.

During 29 May and onwards the intensity of volcanic activity decreased, with only relatively small eruptive plumes that occasionally produced minor tephra fall in the communities surrounding the volcano (CONRED 742). CONRED 748 noted that by the 29th, a total of 2,635 people were in shelters due to the eruption, with close to 800 home either damaged or destroyed. In the following days the attention of the emergency managers shifted from the eruption to the Tropical Storm Agatha, which had much broader extent and impact.

In the Pacaya and Guatamala City region, and along drainages carrying ash-charged run, both disasters combined. Lake AmatitlÁn rose, inundating low lying parts of the town with a water-and-ash mix (see photo documentation of impacts at Boston.com). Figure 59 is a photo taken ~12 km downstream of the Lake’s outlet.

Figure 59. The Pacaya tephra fall combined with storm run from Agnes led to swollen rivers in a ‘dual disaster.’ Those rivers formed new deposits along their beds from large amounts of in-swept debris, in this case including large boulders, trees, and a badly battered vehicle in the foreground. This press photograph was taken on 30 May 2010 as the flood water dropped. The location was the municipality of Palin, which sits along the Michatoya river downstream of Lake AmatitlÁn and ~10 km W of Pacaya. Taken from Boston.com with credit to Johan Ordonez/AFP/Getty Images.

Seismic record. INSIVUMEH and REW (2013) suggested a climax on the 27th starting shortly before 1800 local time and lasting ~40 minutes.

The seismic signal (figure 60, upper panel) contained a few scattered high amplitude events during the morning of 27 May 2010. Seismicity rose significantly about 1200 on the 27th, about doubling the RSAM values recorded during the previous 13 hours.

Figure 60. Seismicity recorded at Pacaya during the 2300 of 26 May through 1700 on 28 May (local times). The upper panel shows the seismic record and the lower panel shows the computed RSAM. Station PCG is a short-period seismometer located on Cerro Chino, ~1 km NW of Pacaya’s summit on the MacKenney cone. Courtesy of INSIVUMEH.

The first of about 10 strong peaks (seen on both the upper and lower panels of figure 60) took place around 1230 on the 27th. Those peaks represented a large escalation in seismicity an approximate doubling of the RSAM values. The highest peak on the record took place during 1730 to 1830 on the 27th, a ~6-fold increase in RSAM over the background values acquired earlier on the 27th. During the middle part of the 1800-1900 interval there was a peculiar several-minute-long period with low seismicity conspicuous on the seismic record (upper panel). After that, a series of closely spaced peaks of generally decreasing amplitude followed and then seismicity decreased substantially, particularly around 2300-2400 on the 27th. A second escalation of broadly similar size to the earlier one came on the 28th peaking at 1100 and then dropping.

In a later analysis of seismicity, Mercado and others (2012 correlated waveforms for 5 months before and 9 months after the May 2010 eruption. They noted that “No correlation was found between the events of each day during the five-month period before the eruption, thus, establishing no relationship with the periods of correlation found after the eruption. The post-eruptive sources of seismicity discovered were not active before the eruptive event of May 27, 2010, and therefore these sources must be strictly post-eruptive in nature.”

Aviation. Although there were 48 reports (Volcanic Ash Advisories, VAA’s or simply ‘advisories’) issued by the Washington Volcanic Ash Advisory Center (VAAC) on Pacaya behavior during the interval 27 May to 26 June 2010, weather clouds frequently masked the plume from the key satellite observation platform, the GOES-13 satellite. Where satellite observations of the plume were scarce or lacking, most of the VAA’s conveyed ground-based observations including media reports.

By the 3rd advisory, which was issued on the 28th, considerable ash had fallen at the International airport Aurora. There is some confusion as to the quantity of ash at the airport and over the region in general, but a photo on the 28th shows ash at the airport. Judging from ash load on the aircraft, the f walking just to the right of the aircraft, and adjacent tire tracks, the ash was on the order of ~1-cm thick (figure 61). This is in accord with INSIVUMEH’s summary report that said 5-7 mm of ash had fallen during the entire explosive 27-28 May eruption at the airport. This is also in accord with REW (2014), which discusses the complexities of assessing tephra thicknesses in more detail, and presents a preliminary isopach map that shows the S fringes of the Guatemala City urban area with 10 cm of ash and many parts of the urban area farther N, including the airport, with on the order of 1 cm of ash.

Figure 61. An American Airlines jet sits covered with ash from the Pacaya explosions at the International airport in Guatemala City on 28 May 2010. Runway cleanup took five days. The cleaning of the abrasive ash both destroyed the bituminous runway surface and all markings on it (Wardman and others, 2012). This photo was posted on the Boston Globe news website (Boston.com, see reference in table 5) with the credit to REUTERS/Daniel LeClair.

What follows is a summary of the advisories issued during 27 through 28 May (UTC).

The VAA’s frequently refer to the NAM (North American Mesoscale Model), a numerical model for short-term weather forecasting and in this case wind-velocity estimation. The model is run 4 times a day with 12 km horizontal resolution and with 1 hour temporal resolution, providing finer detail than other operational forecast models. An example of a model with less detail is the model called GFS (Global Forecast System), which predicts weather for many regions of the world, and was sometimes also used by the VAAC analysts.

The VAAC issued their 1st VAA for Pacaya during 2010 on May 27 at 1140 UTC, citing as key information sources GFS winds and INSIVUMEH. Eruption details noted small brief ash emissions near the summit at 1115 UTC. The ash cloud was not identifiable from the GOES-13 satellite owing to rain. The ash cloud was inferred to have remained low and near the volcano. GFS wind data suggested that for such a low ash cloud at that time, wind-directed transport would carry a plume S-SW and would only be significant for ~20 km. The analyst noted that eruption as then dominantly lava emission.

The 2nd advisory came out 7 hours later at 1845 UTC on the 27th indicating volcanic ash and gases to ~3.5 km altitude (noting ICAO as an information source). Ash was again not identifiable from the GOES-13 satellite owing to clouds.

The 3rd advisory, noting ‘ongoing emission of volcanic ash and gases,’ came out at 1257 UTC on the 28th, again lacking clear satellite identification of ash owing to clouds, in this case citing a thick tropical depression. This advisory relied on both a wind model (NAM winds) and an aviation meteorological report (a METAR). The advisory further noted media reports of ash on runways as discussed in the context of figure 61.

The 4th advisory was issued at 1554 UTC on the 28th, noting “increasing emissions” at 1515 UTC with INSIVUMEH reporting ash rising to 3.7 km altitude (FL 120) and spreading up to 27 km NW. Again, owing to extensive weather clouds, ash was again not visible from GOES-13 satellite.

The 5th advisory was issued at 1710 UTC on the 28th, noting “ongoing emissions” recorded at 1645 UTC. Plume has now become visible in [GOES-13] imagery and extends about 15 NMI [Nautical miles, 27 km] to the NNE of the summit. Plume top was at 3.7 km altitude (FL 120).

The 6th advisory was issued at 1915 UTC on the 28th, noting a large eruption recorded at 1815 UTC: “Large eruption seen to FL420 [42,000 feet, ~13 km altitude] based on NAM sounding for the area. Forecast winds remain mostly westerly to northwesterly. Winds at the time of observation blew the plume E at ~18 km/hr.

The 7th advisory was issued at 1930 UTC on the 28th (the last one that day); it repeated information about the eruption seen in imagery around 1815. In this advisory the wind was moving NW at 27 km/hr.

Slope stability study. Schaefer and others (2013) evaluated slope stability at Pacaya and commented on the possible implications of the trough across the MacKenney cone (figure 57). They consider the trough noted above as an example of a recent, smaller-volume collapse.

Specifically, they studied the SW flank of the edifice and developed a geomechanical model based upon field observations and laboratory tests of intact rocks from Pacaya. Their study included analysis of slope stability using numerical techniques and consideration of forces from gravity, magmatic pressure, and seismic loading as triggering mechanisms for slope failure.

Given the cone’s structural and seismo-tectonic setting, the likely magma pressures, and the history of past behavior, they suggested Pacaya lacked substantial gravitational stability.

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Matías Gómez, RO, Rose, WI, Palma, JL, Escobar-Wolf, R, 2012, Notes on a map of the 1961-2010 eruptions of VolcÁn de Pacaya, Guatemala. Geol Soc Am Digital Map Chart Series 10: 10 pp.

Matías , O., 2010, Volcanological map of the 1961 - 2009 eruption of Volcan de Pacaya, Guatemala. MS. Thesis. Michigan Technological University, Houghton, Michigan. 57 pp.

Mercado, D, Waite, G, and Rodriguez, L, 2012, Analysis of seismic patterns before and after the May 27, 2010 eruption of Pacaya volcano, Guatemala, Cities on Volcanoes 7 (COV7), Abstract volume, IAVCEI meeting (19-23 November 2012, Colima, Mexico) (URL: http://www.citiesonvolcanoes7.com/vistaprevia2.php?idab=510)

Morgan, HA, Harris, AJL, and L. Gurioli, 2013, Lava discharge rate estimates from thermal infrared satellite data for Pacaya Volcano during 2004-2010, Jour.of Volcanology and Geoth. Res., Vol. 264, pp. 1-11, ISSN 0377-0273, http://dx.doi.org/10.1016/j.jvolgeores.2013.07.008.

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Information contacts: Rüdiger Escobar Wolf, Department of Geological Engineering and Sciences, Michigan Tech University, Houghton, MI 49931; INSIVUMEH Seccion Vulcanologia (Institute National de Sismologia, Vulcanologia, Meteorolgia, e Hidrologia) 7a Avenida, Zona 13, Guatemala City, Guatemala; Gustavo Chigna,.INSIVUMEH; CONRED (Coordinadora Nacional para la Reducción de Desastres) Avenida Hincapié 21-72, Zona 13 Guatemala, Ciudad de Guatemala; and Washington Volcanic Ash Advisory Center (VAAC), NOAA Satellite Analysis Branch, NOAA NESDIS OSPO, E/SP, NCWCP, 5830 University Research Court, College Park, MD 20740 (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/).

Geologic Background. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

Information Contacts: Rüdiger Escobar Wolf, Department of Geological Engineering and Sciences, Michigan Tech University, Houghton, MI 49931; INSIVUMEH Seccion Vulcanologia (Institute National de Sismologia, Vulcanologia, Meteorolgia, e Hidrologia) 7a Avenida, Zona 13, Guatemala City, Guatemala; Gustavo Chigna,.INSIVUMEH; CONRED (Coordinadora Nacional para la Reducción de Desastres) Avenida Hincapié 21-72, Zona 13 Guatemala, Ciudad de Guatemala; and Washington Volcanic Ash Advisory Center (VAAC), NOAA Satellite Analysis Branch, NOAA NESDIS OSPO, E/SP, NCWCP, 5830 University Research Court, College Park, MD 20740 (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/).

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 Atmospheric Effects

The enormous aerosol cloud from the March-April 1982 eruption of Mexico's El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin. Descriptions of the initial dispersal of major eruption clouds remain with the individual eruption reports, but observations of long-term stratospheric aerosol loading will be found in this section.

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 Special Announcements

Special announcements of various kinds and obituaries.

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 Additional Reports

Reports are sometimes published that are not related to a Holocene volcano. These might include observations of a Pleistocene volcano, earthquake swarms, or floating pumice. Reports are also sometimes published in which the source of the activity is unknown or the report is determined to be false. All of these types of additional reports are listed below by subregion and subject.


False Report of Sea of Marmara Eruption

Africa (northeastern) and Red Sea

False Report of Somalia Eruption

Africa (eastern)

False Report of Elgon Eruption

Kermadec Islands

Floating Pumice (Kermadec Islands)

1986 Submarine Explosion

Tonga Islands

Floating Pumice (Tonga)

Fiji Islands

Floating Pumice (Fiji)

New Britain


Andaman Islands

False Report of Andaman Islands Eruptions

Sangihe Islands

1968 Northern Celebes Earthquake

Kawio Barat


False Report of Mount Pinokis Eruption

Southeast Asia

Pumice Raft (South China Sea)

Land Subsidence near Ham Rong

Ryukyu Islands and Kyushu

Pumice Rafts (Ryukyu Islands)

Izu, Volcano, and Mariana Islands

Mikura Seamount

Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source

Kuril Islands

Possible 1988 Eruption Plume



Aleutian Islands

Possible 1986 Eruption Plume


False Report of New Volcano




La Lorenza Mud Volcano



Pacific Ocean (Chilean Islands)

False Report of Submarine Volcanism

Central Chile and Argentina

Estero de Parraguirre

West Indies

Mid-Cayman Spreading Center

Atlantic Ocean (northern)

Northern Reykjanes Ridge


Azores-Gibraltar Fracture Zone

Antarctica and South Sandwich Islands

Jun Jaegyu

East Scotia Ridge

 Special Announcements

Special Announcement Reports