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Westdahl

Photo of this volcano
  • Country
  • Primary Volcano Type
  • Last Known Eruption
  •  
  • 54.516°N
  • 164.65°W

  • 1563 m
    5128 ft

  • 311340
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number
Most Recent Weekly Report: 14 October-20 October 2020 Citation IconCite this Report

AVO reported that the seismic network at Westdahl has been re-established, again allowing seismic unrest at the volcano to be monitored. The Volcano Alert Level and Aviation Color Code were changed from Unassigned to Normal and Green, respectively, on 15 October.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


Most Recent Bulletin Report: January 1992 (BGVN 17:01) Citation IconCite this Report

Eruption apparently ends; seismic data from eruption onset

Westdahl's eruption appears to have stopped. Poor weather limited observations and the stop date is uncertain, but a significant decrease in eruption intensity was noted on 15 January. Geologists noted that comparison with the 1978 eruption suggested that this cessation in activity may be only a pause.

No plume penetrated the cloud deck that obscured the summit-area fissure during a 23 January overflight. The lava flow appears to have widened to cover 2-3 times its 3 December area (figure 5), while its front had not advanced significantly. As of late January, infrared images from the NOAA-11 polar orbiting weather satellite indicated a "warm" spot in the vicinity of the volcano. Exact registration of the warm area has been difficult, but it is believed to be associated with the position of the cooling lava flow. The FAA removed all flight restrictions around the volcano on 7 February. During aerial observations by FWS personnel on 13 February, only scattered steaming was noted from the flow. Minor steaming occurred from a small cinder cone near a steep, ice-walled canyon, where the fissure vent cuts the E part of the summit glacier.

Information Contacts: AVO.

Weekly Reports - Index


2020: October


14 October-20 October 2020 Citation IconCite this Report

AVO reported that the seismic network at Westdahl has been re-established, again allowing seismic unrest at the volcano to be monitored. The Volcano Alert Level and Aviation Color Code were changed from Unassigned to Normal and Green, respectively, on 15 October.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


Bulletin Reports - Index

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

01/1978 (SEAN 03:01) Large new explosive eruption

02/1978 (SEAN 03:02) Major ash eruption (about six days)

05/1978 (SEAN 03:05) February ashfall on vessel 1,000 km SE of Westdahl

09/1978 (SEAN 03:09) February eruption site visited; new crater 1.5 km in diameter and 0.5 km deep

02/1979 (SEAN 04:02) 8-km cloud seen on satellite imagery

11/1991 (BGVN 16:11) Lava flows and tephra from 8-km NE-flank fissure

12/1991 (BGVN 16:12) Tephra emission declines

01/1992 (BGVN 17:01) Eruption apparently ends; seismic data from eruption onset




Information is preliminary and subject to change. All times are local (unless otherwise noted)


January 1978 (SEAN 03:01) Citation IconCite this Report

Large new explosive eruption

The USCG reported on 6 February that ash, accompanied by a sulfur odor, was falling on a station located at the foot of Westdahl. Lightning was observed above the summit, accompanied by thunder and rumbling. The summit is not visible from the Coast Guard station and cloud cover has prevented direct aerial observation of the group of volcanoes which includes stratovolcanoes Westdahl and Pogromni, active in historical time. However, Reeve Aleutian Airways personnel report an ash cloud rising to 8-10 km altitude, including some large blocks visible above the 3-km cloud layer. Satellite images returned 5 February show a well-developed ash cloud, but it has not yet been possible to pinpoint the eruption start time [see 3:9].

Information Contacts: T. Miller, USGS, Anchorage.


February 1978 (SEAN 03:02) Citation IconCite this Report

Major ash eruption (about six days)

Data from satellite imagery and aircraft observations established that the eruption originated from the summit of Westdahl, one of five volcanoes on Unimak Island active in historical times. The eruption column was first visible in 5 February satellite imagery (figure 1), but Coast Guard personnel from Scotch Cap (15 km SW of Westdahl's summit) noted a sulfur odor during the evening of the 3rd and reported that ash had begun to fall by the next morning. Eruption column height was estimated at 8-10 km from aircraft observations on 6 February (figure 2) and up to 8 km from interpretation of satellite imagery (figure 3). Nearly 1 m of ash fell at Scotch Cap, forcing evacuation of its personnel and damaging Scotch Cap Light. Meltwater caused stream flooding and washed out the coast road. A Reeve Aleutian Airways pilot observed a new cinder cone, about 100 m in diameter, located near the site of Westdahl's last eruption (March-April, 1964). No lava flow has been observed. Activity declined to steaming after 9 February.

Figure (see Caption) Figure 1. Enlargement of a portion of a NOAA 5 infrared image at 1835 on 8 February 1978 (0.9-km ground resolution), showing plumes, each about 60 km long, extending SE from both Westdahl and Shishaldin. Most of the Alaska Peninsula is visible, as is the coast of Alaska NW to the entrance to Kuskokwim Bay. The gray area off the coast is pack ice. Courtesy of Jürgen Kienle and NOAA.
Figure (see Caption) Figure 2. Oblique airphoto taken 6 February 1978 by George Wooliver (Reeve Aleutian Airways), showing Westdahl's eruption column emerging from the cloud layer at about 3000 m altitude. Wind is from the N at about 130 km/hr. Wooliver estimated that the top of the eruption column was at 8-10 km altitude. Courtesy of Thomas Miller.
Figure (see Caption) Figure 3. NOAA 5 satellite imagery, 5-9 February 1978, showing Unimak Island and vicinity. North orientations (arrow) are the same for each. A: (5 February 1978, 1036, infrared) Plume extends about 230 km S, rising to an estimated 8 km; black summit hot spot. B: (6 February 1978, 1141, infrared) Plume extends about 110 km SE; black summit hot spot. C: (7 February 1978, 1101, infrared) Plume at least 6 km high and about 160 km long, blown primarily SSE but some eastward shearing evident, probably by lower altitude winds. D: (8 February 1978, 1018, infrared) Plume extends 80 km SSE, at lower altitude than in C. E: (8 February 1978, 1018, visible, enlarged about 50% more than A-D) Weak plume curves SW to W about 100 km. Shishaldin is no longer active, 16 hours after its plume was visible in figure 11-2. The dark triangular area S of Westdahl is fresh ashfall, subtending an angle of about 95° and covering an area of about 300 km2. No ashfall is visible on Shishaldin. Courtesy of Jürgen Kienle and NOAA.

Information Contacts: J. Kienle, Univ. of Alaska; T. Miller, USGS, Anchorage.


May 1978 (SEAN 03:05) Citation IconCite this Report

February ashfall on vessel 1,000 km SE of Westdahl

Snow contaminated by dark ash fell on the freight vessel United Spirit between 1200 and about midnight on 7 February, as it steamed from 48.8°N, 152.5°W to 49.2°N, 156.3°W, about 1,000 km SE of Westdahl. Satellite imagery (figure 3) shows that winds were driving the eruption cloud towards the vessel, about 24 hours before the ashfall began. Winds observed from the United Spirit during the snowfall were steadily from the NW.

Information Contacts: JMA, Tokyo.


September 1978 (SEAN 03:09) Citation IconCite this Report

February eruption site visited; new crater 1.5 km in diameter and 0.5 km deep

On 6-7 August a team of six, including volcanologists Maurice and Katia Krafft and Alain Gerente, climbed Westdahl. The new crater formed by the February eruption is about 1.5 km in diameter and 0.5 km deep, at about 1450 m elevation (figure 4). Its upper portion cut through glacial ice, which reached 200 m thickness on the N rim. The bottom of the vertical-walled crater is filled with blocks, ash, ice, and talus.

Figure (see Caption) Figure 4. Sketch map with cross section of Westdahl's February eruption crater and vicinity, prepared by Maurice Krafft from observations made during a visit 6-7 August 1978.

A lahar deposit, originating on the WSW flank of the new crater, extended down the glacier on Westdahl's flank to the sea, cutting the road from Cape Sarichef to Scotch Cap. The thickness of the upper portion of the deposit averaged about 50 cm, increasing to 1-3 m near the lower end.

A diary from Richard Clark (who was at Scotch Cap during the eruption) has established that the eruption began about 1330 on 4 February with the ejection of a steam cloud. Ash emission began soon afterward and ashfall started at Scotch Cap (15 km SW of the crater) at about 1600. A thunderstorm associated with the activity dropped hailstones formed around particles of ash and small lapilli. Tephra fall and the associated thunderstorm continued at Scotch Cap until mid-afternoon on 5 February. Clark reported that ash emission was continuing when he left the area during the morning of 8 February. A plume was visible in a satellite image at 1129 on 9 February (3:2). After the 9th, activity declined to steaming.

Information Contacts: M. Krafft, Cernay; R. Clark, Blaine WA.


February 1979 (SEAN 04:02) Citation IconCite this Report

8-km cloud seen on satellite imagery

A cloud apparently erupted from Westdahl was present on NOAA weather satellite imagery for more than 30 hours on 8 and 9 February. The cloud was first observed on an infrared image at 0352 on 8 February, about 17 hours after the previous image, on which no eruption cloud could be seen. A cloud was present on successive images on the 8th at 0926 (visible and infrared) and on the 9th at 0842 and 1037 (infrared) but not at 1958 on the 9th or 0952 on the l0th. The cloud was no more than 50 km in longest dimension on any of the images, nor was it elongated into a typical volcanic plume.

The height of the cloud was calcuated separately from infrared and visual images taken at 0926 on 8 February. Analysis of the infrared image gives a temperature of -53°C at the top of the cloud, corresponding to an altitude of slightly more than 8 km. On the visual image, measurements of the shadow cast on the weather cloud deck by the volcanic cloud result in an estimated altitude of 7.7 ± 1 km.

No activity was reported from the USCG LORAN Station at Cape Sarichef, less than 25 km from Westdahl, nor was there any aircraft confirmation of the activity.

Information Contacts: F. Parmenter, NOAA/NESS, Anchorage; J. Kienle, Univ. of Alaska; USCG LORAN Station, Unimak Island.


November 1991 (BGVN 16:11) Citation IconCite this Report

Lava flows and tephra from 8-km NE-flank fissure

Westdahl erupted at approximately 1700 on 29 November, sending a plume of steam and ash to more than 6 km altitude. The FAA immediately rerouted air traffic to the Pacific side of the eastern Aleutians to avoid encounters with the plume, which drifted NNE over the Bering Sea.

Video and still photographs from 30 November (courtesy of the U.S. Coast Guard, Peninsula Airways, and several civilians) show that the eruption occurred from a fissure, ~8 km long, extending down the NE flank from Westdahl Peak to an elevation of ~760 m. Several large craters and gaping sinuous cracks, parallel to the fissure, formed in snow and ice fields, probably by collapse due to melting. Ash venting occurred discontinuously along most of the fissure's length, but lava fountaining was concentrated along the lower few kilometers. Several streams of fluid lava traveled E down at least two steep-walled drainages. By the second day of the eruption, the principal lava flow had moved a distance of about 4 km. Based on observations by AVO staff from a Coast Guard C-130 aircraft on 3 December, the very active flow front was 1.5 km wide, 5-10 m high, and ~7 km from the vent [figure 5]. The lava flow consisted of blocky gray aa, and widened as it reached the broad valley draining to the Pacific Ocean. As of 3 December, the front was about 10 km from the ocean. Also observed on the overflight was a dark-colored debris-flow deposit that extended to the Pacific. Streams draining the NE flank were muddy and steaming slightly when observed on 30 November and 3 December. Lava fountaining was visible, during clear weather, through 10 December, and lava flows remained active on the NE flank.

Figure (see Caption) Figure 5. Sketch map of the SW part of Unimak Island, showing the eruption vents and lava flow from the Westdahl eruption as of 3 December 1991. Contour interval, 1,000 feet (about 300 m). Printed by permission of the Alaska Volcano Observatory. [Originally in 17:01]

Satellite imagery and pilot observations through mid-December indicated that the steam plume, periodically containing small quantities of ash, rose to as much as 7 km altitude and was preferentially carried NE. On 30 November, residents of False Pass, 90 km NE, reported ash-laden skies, fine ash deposition, and a strong sulfur smell that lasted into the night. Similar strong sulfur odors were reported by pilots up to several hundred kilometers inland. Light ashfall occurred again at False Pass on 9 and 12 December, and distant roaring and rumbling were occasionally heard at night through mid-December. No ash was reported in Cold Bay (145 km NE).

[No seismometers are installed on Westdahl, so information about seismicity associated with the eruption is limited. Data from the nearest seismic station, 170 km ENE of Westdahl (at Dutton), included six earthquakes of M 2.8-3.1 between 1100 and 1940 on 29 November. S-P values were consistent with epicenters in the Westdahl area, as were those recorded at Sand Point, 275 km ENE. The Dutton station also detected a tremor-like signal, different from typical noise at the site, between 1500 and 1949 on 29 November. (Originally in 17:01).]

Further Reference. Swanson, S., 1990, Westdahl, in Wood, C. and Kienle, J., Volcanoes of North America: Cambridge University Press, p. 45-46.

Information Contacts: AVO; SAB; AP.


December 1991 (BGVN 16:12) Citation IconCite this Report

Tephra emission declines

The eruption ... continued until 15 January when a significant decrease in activity was noted. Bad weather prevented further observations of the lava flow. Aircraft pilots reported steam and ash plumes to 3.7-7.0 km altitude on 16-20 December, and 4.9 km altitude on 21-23 December. Light ashfall was noted on 16, 25, and 26 December at False Pass, 90 km NE. Residents of False Pass reported hearing rumbling for several nights prior to 30 December. Analyses of ash samples (collected 9 and 25 December) indicated a basaltic andesite composition, with [54.7]% SiO2.

Steam clouds rose to 4.6-4.9 km altitude on 2 and 3 January. Ash clouds were again observed on 8 and 9 January, rising to 2.1-2.4 km altitude. Satellite images during the late afternoon on the 9th showed the plume extending about 150 km SE. A dark spot appeared in satellite images of the volcano for several days prior to 13 January, indicating high temperatures. A black ash cloud was reported to 4 km on 13 January.

The eruption was greatly diminished in intensity on 15 January. Observers noted a small amount of steam at ground level in the vicinity of the eruption site, but there was no sign of a vertical plume. That day, an elongate area of slightly elevated temperature on the volcano's NE flank was visible in a satellite image.

[A 23 January overflight provided the first clear view of the lava flow since 3 December. The flow appeared to have widened to cover 2-3 times its 3 December area, but its front had not advanced significantly.]

Information Contacts: AVO.


January 1992 (BGVN 17:01) Citation IconCite this Report

Eruption apparently ends; seismic data from eruption onset

Westdahl's eruption appears to have stopped. Poor weather limited observations and the stop date is uncertain, but a significant decrease in eruption intensity was noted on 15 January. Geologists noted that comparison with the 1978 eruption suggested that this cessation in activity may be only a pause.

No plume penetrated the cloud deck that obscured the summit-area fissure during a 23 January overflight. The lava flow appears to have widened to cover 2-3 times its 3 December area (figure 5), while its front had not advanced significantly. As of late January, infrared images from the NOAA-11 polar orbiting weather satellite indicated a "warm" spot in the vicinity of the volcano. Exact registration of the warm area has been difficult, but it is believed to be associated with the position of the cooling lava flow. The FAA removed all flight restrictions around the volcano on 7 February. During aerial observations by FWS personnel on 13 February, only scattered steaming was noted from the flow. Minor steaming occurred from a small cinder cone near a steep, ice-walled canyon, where the fissure vent cuts the E part of the summit glacier.

Information Contacts: AVO.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Eruptive History

There is data available for 7 confirmed Holocene eruptive periods.

1991 Nov 29 - 1992 Jan 14 Confirmed Eruption Max VEI: 3

Episode 1 | Eruption Episode ENE flank (1560-760 m)
1991 Nov 29 - 1992 Jan 14 Evidence from Observations: Reported

List of 6 Events for Episode 1 at ENE flank (1560-760 m)

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Lava fountains
   - - - -    - - - - Lava flow
   - - - -    - - - - Ash
   - - - -    - - - - Lahar or Mudflow
1991 Nov 29    - - - - VEI (Explosivity Index)

[ 1979 Feb 8 - 1979 Feb 9 ] Uncertain Eruption

Episode 1 | Eruption Episode
1979 Feb 8 - 1979 Feb 9 Evidence from Unknown

List of 3 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain
   - - - -    - - - - Eruption cloud
1979 Feb 8    - - - - VEI (Explosivity Index)

1978 Feb 4 - 1978 Feb 9 Confirmed Eruption Max VEI: 3

Episode 1 | Eruption Episode South of Westdahl Peak (1450 m)
1978 Feb 4 - 1978 Feb 9 Evidence from Observations: Reported

List of 10 Events for Episode 1 at South of Westdahl Peak (1450 m)

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Eruption cloud
   - - - -    - - - - Cinder Cone
   - - - -    - - - - Blocks
   - - - -    - - - - Lightning
   - - - -    - - - - Crater Summit.
   - - - -    - - - - Lahar or Mudflow
   - - - -    - - - - Property Damage
   - - - -    - - - - Evacuations
1978 Feb 4    - - - - VEI (Explosivity Index)

1964 Mar 10 - 1964 Apr 16 Confirmed Eruption Max VEI: 2

Episode 1 | Eruption Episode
1964 Mar 10 - 1964 Apr 16 Evidence from Observations: Reported

List of 5 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Lava flow
   - - - -    - - - - Ash
   - - - -    - - - - Earthquakes (undefined) Before.
1964 Mar 10    - - - - VEI (Explosivity Index)

1827 - 1830 Confirmed Eruption Max VEI: 2

Episode 1 | Eruption Episode Pogromni or (more likely) Westdahl
1827 - 1830 Evidence from Observations: Reported

List of 4 Events for Episode 1 at Pogromni or (more likely) Westdahl

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion weak or small
   - - - -    - - - - Ash
   - - - -    - - - - Flames
1827    - - - - VEI (Explosivity Index)

1820 Confirmed Eruption Max VEI: 2

Episode 1 | Eruption Episode Pogromni or (more likely) Westdahl
1820 - Unknown Evidence from Observations: Reported

List of 2 Events for Episode 1 at Pogromni or (more likely) Westdahl

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion weak or small
1820    - - - - VEI (Explosivity Index)

1796 Confirmed Eruption Max VEI: 0

Episode 1 | Eruption Episode Pogromni or (more likely) Westdahl
1796 - Unknown Evidence from Observations: Reported

List of 3 Events for Episode 1 at Pogromni or (more likely) Westdahl

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Lava flow
   - - - -    - - - - Lahar or Mudflow
1796    - - - - VEI (Explosivity Index)

1795 Confirmed Eruption Max VEI: 4

Episode 1 | Eruption Episode Pogromni or (more likely) Westdahl
1795 - Unknown Evidence from Observations: Reported

List of 4 Events for Episode 1 at Pogromni or (more likely) Westdahl

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion violent, strong, or large
   - - - -    - - - - Ash
   - - - -    - - - - Lahar or Mudflow
1795    - - - - VEI (Explosivity Index)
Deformation History

There is data available for 2 deformation periods. Expand each entry for additional details.


Deformation during 1992 - 2010 [Uplift; Observed by InSAR]

Start Date: 1992 Stop Date: 2010 Direction: Uplift Method: InSAR
Magnitude: Unknown Spatial Extent: Unknown Latitude: Unknown Longitude: Unknown

Remarks: Inflation persists but rates diminish with time following the 1991 eruption. There is a gap in InSAR coverage between 2000 and 2003.

Figure (see Caption)

Observed (left column) and corresponding model (right column) interferograms of Westdahl Peak for various time periods during 1992?2000, showing progressive inflation. Each fringe (full color cycle) represents 2.83 cm of range change between the ground and the satellite. Areas that lack interferometric coherence are uncolored

From: Lu and Dzurisin 2014.


Reference List: Lu et al. 2000; Lu et al. 2003c; Lu and Dzurisin 2014; Mann and Freymueller 2003; Gong et al. 2015.

Full References:

Gong, W., Meyer, F. J., Lee, C. W., Lu, Z., & Freymueller, J., 2015. Measurement and interpretation of subtle deformation signals at Unimak Island from 2003 to 2010 using weather model- assisted time series InSAR. J. Geophys. Res., 120(2), 1175-1194.

Lu Z, Dzurisin D, 2014. InSAR imaging of Aleutian volcanoes: monitoring a volcanic arc from space. Springer-Verlag Berlin Heidelberg. https://doi.org/10.1007/978-3-642-00348-6

Lu, Z., J. C. Wicks, D. Dzurisin, W. Thatcher, J. T. Freymueller, S. R. McNutt, and D. Mann, 2000. Aseismic inflation of Westdahl volcano, Alaska, revealed by satellite radar interferometry. Geophysical Research Letters, 27, 1567-1570. https://doi.org/10.1029/1999GL011283

Lundgren, P., P. Berardino, M. Coltelli, G. Fornaro, R. Lanari, G. Puglisi, E. Sansosti, and M. Tesauro,, 2003. Coupled magma chamber inflation and sector collapse slip observed with synthetic aperture radar interferometry on Mt. Etna volcano. J. Geophys. Res., 108(B5), 2247. https://doi.org/10.1029/2001JB000657

Mann D, Freymueller J, 2003. Volcanic and tectonic deformation on Unimak Island in the Aleutian Arc, Alaska. J. Geophys. Res., 108(B2), 2108. https://doi.org/10.1029/2002JB001925

Deformation during 1991 Nov 21 - 1991 Nov 30 [Subsidence; Observed by InSAR]

Start Date: 1991 Nov 21 Stop Date: 1991 Nov 30 Direction: Subsidence Method: InSAR
Magnitude: 6.000 cm Spatial Extent: Unknown Latitude: Unknown Longitude: Unknown

Remarks: Co-eruptive subsidence due to magma withdrawal is observed during the 1991 eruption of Westdahl.

Figure (see Caption)

a?d Observed InSAR images of Westdahl that span periods from several days to several weeks shortly before the start of the 1991?1992 eruption. e, f Observed and model InSAR images showing surface subsidence (deflation) during the first 20 h of the eruption. g, h Observed InSAR images that each span a 6-day period shortly after the end of the eruption. In all cases, each fringe (full color cycle) represents 2.83 cm of range change between the ground and the satellite and areas that lack interferometric coherence are uncolored

From: Lu and Dzurisin 2014.


Reference List: Lu et al. 2000; Lu et al. 2003c; Lu and Dzurisin 2014.

Full References:

Lu Z, Dzurisin D, 2014. InSAR imaging of Aleutian volcanoes: monitoring a volcanic arc from space. Springer-Verlag Berlin Heidelberg. https://doi.org/10.1007/978-3-642-00348-6

Lu, Z., J. C. Wicks, D. Dzurisin, W. Thatcher, J. T. Freymueller, S. R. McNutt, and D. Mann, 2000. Aseismic inflation of Westdahl volcano, Alaska, revealed by satellite radar interferometry. Geophysical Research Letters, 27, 1567-1570. https://doi.org/10.1029/1999GL011283

Lundgren, P., P. Berardino, M. Coltelli, G. Fornaro, R. Lanari, G. Puglisi, E. Sansosti, and M. Tesauro,, 2003. Coupled magma chamber inflation and sector collapse slip observed with synthetic aperture radar interferometry on Mt. Etna volcano. J. Geophys. Res., 108(B5), 2247. https://doi.org/10.1029/2001JB000657

Emission History

There is no Emissions History data available for Westdahl.

Photo Gallery

This roughly 50-cm-long volcanic bomb, erupted from Westdahl volcano in the Aleutians, is known as a spindle bomb. Molten masses of magma that are blown out of the crater commonly become aerodynamically rounded into a spindle shape as they are hurled through the air. Some bombs are still partially molten and become deformed when they impact onto the ground.

Copyrighted photo by Katia and Maurice Krafft, 1978.
A lahar produced by the melting of snow and ice during a February 4-9, 1978 eruption of Westdahl volcano in the Aleutians is seen in the foreground of this summer 1978 photo taken near Scotch Cap on the SW coast. The lahar traveled 12 km from the summit, visible at the upper left. The 1978 eruption blasted a 1.5-km wide, 500-m deep crater through the summit icecap.

Copyrighted photo by Katia and Maurice Krafft, 1978.
An explosive eruption February 4-9, 1978, produced an 8-10 km-high eruption column and blasted a new 1.5-km-wide, 0.5-km-deep crater through the summit icecap 1 km south of Westdahl Peak. This view from the west rim shows the summit icefield at the top of the new crater; the icefield was truncated by the explosions.

Copyrighted photo by Katia and Maurice Krafft, 1978.
The summit area of Westdahl, located on the southwestern part of Unimak Island in the eastern Aleutians, is seen here from the east. Westdahl Peak (left) and Faris Peak (right) formed on the broad main edifice. The scoria cone in the center was the principal eruption site for the 1991-92 activity, producing the snow-covered lava flow in the foreground. . The sinuous fissure cutting across the glacial icecap from the summit formed in the opening phases of the eruption and produced lava fountaining.

Photo by C.F. Zeillemaker, 1993 (U.S. Fish and Wildlife Service, courtesy of Alaska Volcano Observatory).
This 1992 view up the eastern flank of Westdahl was taken two months after the end of a major eruption that produced these lava flows. The eruption took place from an 8-km-long fissure that extended from the summit down the east flank and began on 29 November 1991 with a 6-km-high ash plume. The lava flow traveled as far as 7 km from the vent, widening as it reached the lower flanks.

Photo by C. Dau, 1992 (U.S. Fish and Wildlife Service, courtesy of Alaska Volcano Observatory).
GVP Map Holdings

The maps shown below have been scanned from the GVP map archives and include the volcano on this page. Clicking on the small images will load the full 300 dpi map. Very small-scale maps (such as world maps) are not included. The maps database originated over 30 years ago, but was only recently updated and connected to our main database. We welcome users to tell us if they see incorrect information or other problems with the maps; please use the Contact GVP link at the bottom of the page to send us email.

Smithsonian Sample Collections Database

There are no samples for Westdahl in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

External Sites