A thermal anomaly in the crater of Cleveland was visible on satellite imagery during 25-26 July. The Volcanic Alert Level remained at Watch and the Aviation Color Code remained at Orange through at least 30 July. On the 27th AVO noted that low-level eruptive activity continued. Three small SO₂ clouds produced by small explosions on 20 July were detected in OMI satellite data provided by the University of Maryland Baltimore County. No further explosive activity had been detected by the OMI sensor since that time. AVO is unable to track local earthquake activity related to volcanic unrest.

Sources: US Geological Survey Alaska Volcano Observatory (AVO), OMI Sulfur Dioxide Group

CVGHM lowered the Alert Level for Gamkonora from 3 to 2 (on a scale of 1-4) on 24 July based on visual observations and a decrease in seismicity. That followed a sharp drop in seismicity during 8-23 July, a decline both in terms of the number of events and their energy. Later, during 16-23 July, when breaks in inclement weather took place, observers saw white plumes rising to altitudes of 5.6 km (18,400 ft) a.s.l. Available CVGHM reports issued through the 26 July did not disclose more recent events.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

An important new eruption initiated at Kīlauea very early on 21 July. It occurred along the E rift zone from fissures trending ENE for several kilometers from Pu'u O'o. The fissures caused drainage of both the West Gap lava lake and the Puka Nui pit. These and following events have come to be called the 21 July eruption and an associated fissure system by the same name.

As of 25 July, the 21 July eruption included instability at Puʻu ʻŌʻō, fissuring along an NE-trending zone stretching a bit over 2 km in length, and lava flows over an area of a little over 1 km².

A noteworthy feature of this eruption during the week 25-31 July was the formation of a series of perched ponds of lava. These formed as the edges of pools of lava hardened to create confining walls. These walls enable the pond's surface to be much higher--in some cases as much as 5 m (15 feet) higher than the surrounding land--like a volcanic above-ground swimming pool. During the 21 July eruption the walls of these perched ponds breached repeatedly, allowing lava to suddenly flood surrounding terrain. For example, at least three perched lava ponds breached by the 25th, each breakage spawning radially directed lava flows. Other small lava flows also emerged from fissures during the week as well.

The behavior of the perched ponds is difficult to judge and accordingly, around the start of this week the area was closed to the public. The eruption resided completely within the Kahauale'a Natural Area Reserve (just NE of the Hawaiʻi Volcanoes National Park).

On the morning of the 26th, an M 3.2 earthquake occurred on the lower E rift zone, beneath Pu'ulena crater, at a depth of 3 km (2 miles). Lava ponds again formed in the area surrounding the fissures but views of the process were hampered by foul weather. The HVO update for 31 July noted two prominent lava ponds then. In addition, one of the fissures fed an 'a'a flow advancing to the NE around the N side of Kupaianaha.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

Ol Doinyo Lengai is frequently the scene of fluid but very small volume lava flows in its summit crater, including a few that passed over the crater rim and begun the long descent down the mountain. As noted here last week, news reports had indicated that products of the volcano's 19-July eruption had entered inhabited areas. Subsequent investigations have cast doubt on those earlier claims.

Discussions this week by volcanologist Gerald Ernst with contacts in the region revealed that neither aviators, guides, scientists, nor locals had seen dramatic eruptive events at the mountain. The summit crater was intact, but eruptions were confined to the summit area. What was interpreted from a distance as a modest landslide in the crater may have sent out a dust cloud. That cloud could have been confused with ash from a large flank eruption.

To help shed light on the situation, Greg Vaughan of the Jet Propulsion Labs had a preliminary look at some ASTER satellite data of the volcano and concluded that in mid-June through late July the summit crater was likely to have continued to emit lava. The 20 July thermal emissions appeared no larger than those on 18 June. Those from 15 April appeared weaker. The images supported summit lava eruptions but failed to document any lava that had spilled over the crater rim.

Sources: Greg Vaughan, Jet Propulsion Laboratory, Gerald Ernst, Centre for Environmental & Geophysical Flows, Department of Earth Sciences, University of Bristol

Based on a pilot report, the Darwin VAAC reported that an ash plume possibly from Raung rose to an altitude of 1.5 km (5,000 ft) a.s.l. Ash was not visible on satellite imagery.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)

A KVERT report issued for Karymsky on 27 July stated the following, "The eruption of the volcano continues. Ash explosions up to 6 km (or 19,700 ft.) a.s.l. are possible at any time. The activity of the volcano could affect low-flying aircraft in the vicinity of the volcano."

Based on a report from unstated source and posted by the Tokyo VAAC, on 28 July ash plumes rose to estimated altitudes of ~6 km (20,000 ft) a.s.l., but the plume could not be identified in satellite analysis. The Level of Concern Color Code remained at Orange.

Sources: Tokyo Volcanic Ash Advisory Center (VAAC), Kamchatkan Volcanic Eruption Response Team (KVERT)

Based on pilot observations, the Washington VAAC reported that an ash plume from Sangay rose to an altitude of 6.7-8.2 km (22,000 to 27,000 ft) a.s.l. on 28 July. Ash was not detected on satellite imagery but a weak hotspot could be seen.

Source: Washington Volcanic Ash Advisory Center (VAAC)

KVERT reports noted that seismic activity at Shiveluch continued above background levels during 20-27 July. Based on seismic interpretation, during this interval ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. Gas-and-steam plumes with some ash rose to altitudes of 3.0-4.5 km (9,800-14,800 ft) a.s.l. during 20-24 July. Based on satellite imagery, gas-and-steam plumes drifted S on 22 July and a large thermal anomaly was detected in the crater during 20-27 July. Through at least 27 July, the Level of Concern Color Code remained at Orange.

Sources: Tokyo Volcanic Ash Advisory Center (VAAC), Kamchatkan Volcanic Eruption Response Team (KVERT)

MVO reported that based on visual observations, the lava dome at Soufrière Hills changed very little during 25-26 July. Seismic activity was very low and low-level rockfall activity continued. The Alert Level remained elevated at 4 (on a scale of 0-5).

Source: Montserrat Volcano Observatory (MVO)

Data from deformation-monitoring instruments indicated that during 25-31 July lava-dome growth at Mount St. Helens continued. Seismicity persisted at low levels.

Source: US Geological Survey Cascades Volcano Observatory (CVO)

Based on information from JMA and a pilot report, the Tokyo VAAC reported that an ash plume from Suwanose-jima rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted SW on 26 July. Ash was not visible on satellite imagery.

Source: Tokyo Volcanic Ash Advisory Center (VAAC)

As noted by the IG in their daily reports covering 25-31 July, Tungurahua emitted a substantial number of small ash-bearing explosions and several unusually large ones as well. Based on ground observer estimates, many plumes during the reporting interval rose to 2-3 km above the crater rim (up to ~1 mile above the crater) and dropped ash on towns located on the volcano's flanks.

On the 26th, the IG reported one of the larger explosions, the biggest since March 2007 (its seismic signal yielded a reduced displacement of 9.2 cm²). Associated ashfalls affected some parts of the volcano. The explosion took place at night and the plume height was not estimated.

On the 30th IG observers witnessed another strong explosion that generated a heavily ash-laden plume. The dense portion of the plume rose 400 m above the crater rim. A similar plume had not been seen since 16 August 2006. The associated column of less dense material rose to 3 km and visible portions of dense material appeared as a curtain of ash deposited to the W. Some blocks associated with the outburst rolled up to 0.5 km below the crater's rim. Visibility hampered further observations that day but the many emission noises included the hammering of bouncing blocks.

Tungurahua's 25-31 July activity spurred numerous VAAC reports, but satellite analysts generally had great difficulty with cloudy conditions and few if any plumes were clearly detected.

Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN), Washington Volcanic Ash Advisory Center (VAAC)

Based on a Significant Meteorological Information (SIGMET) advisory, the Buenos Aires VAAC reported that ash plumes from Ubinas rose to an altitude of 5.8 km (19,000 ft) a.s.l. on 23 and 25 July. The plumes drifted SE and S, respectively. Ash was not identified on satellite imagery. On 24 July, a diffuse plume was visible on satellite imagery at an altitude of 6.1 km (20,000 ft) a.s.l.

Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)