Kasatochi

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  • Country
  • Subregion Name
  • Primary Volcano Type
  • Last Known Eruption
  • 52.177°N
  • 175.508°W

  • 314 m
    1030 ft

  • 311130
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

3 September-9 September 2008

AVO reported that during 3-9 September seismic activity from Kasatochi, detected by stations approximately 40 km W on Great Sitkin island, was low. Vigorous steam-and-gas plumes that rose above the crater and drifted up to 32 km downwind were observed on 3 and 4 September by passing mariners. On 4 September the Volcano Alert Level was lowered to Advisory and the Aviation Color Code to Yellow. Clouds mostly prevented satellite image observations; weak thermal anomalies were detected on 5 and 7 September.

Source: US Geological Survey Alaska Volcano Observatory (AVO)



 Available Weekly Reports


2008: August | September


3 September-9 September 2008

AVO reported that during 3-9 September seismic activity from Kasatochi, detected by stations approximately 40 km W on Great Sitkin island, was low. Vigorous steam-and-gas plumes that rose above the crater and drifted up to 32 km downwind were observed on 3 and 4 September by passing mariners. On 4 September the Volcano Alert Level was lowered to Advisory and the Aviation Color Code to Yellow. Clouds mostly prevented satellite image observations; weak thermal anomalies were detected on 5 and 7 September.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


27 August-2 September 2008

AVO reported that during 27 August-2 September seismic activity from Kasatochi detected by stations on Great Sitkin, approximately 40 km W, declined. Clouds prevented satellite image observations. The Volcano Alert Level remained at Watch and the Aviation Color Code at Orange.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


20 August-26 August 2008

AVO reported that during 20-26 August seismic activity from Kasatochi was detected by stations on Great Sitkin, approximately 40 km W. Clouds prevented satellite image observations. Active fumaroles and hot pyroclastic flow deposits over much of the volcano were observed on 22 August by a visiting scientist. On 23 August, the smell of sulfur was reported in the town of Adak. The Volcano Alert Level remained at Watch and the Aviation Color Code at Orange.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


13 August-19 August 2008

AVO reported that during 13-19 August seismic activity from Kasatochi was detected by stations on Great Sitkin, about 40 km W. Clouds prevented satellite image observations. On 17 August, the smell of sulfur was reported in the town of Adak. The Volcano Alert Level remained at Watch and the Aviation Color Code at Orange.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


6 August-12 August 2008

On 6 August, AVO raised the Volcano Alert Level for Kasatochi to Advisory and the Aviation Color Code to Yellow based on increased seismicity detected that day by instruments in the area and by field crews on the island the previous few days. Kasatochi lacks dedicated seismometers and is monitored by neighboring networks.

On 7 August, earthquake activity continued; events as large as M 5.6 were detected. Crews reported rockfalls, ground shaking lasting 5-10 minutes, and a strong sulfur smell. Periods of volcanic tremor prompted AVO to raise the Volcano Alert Level to Watch and the Aviation Color Code to Orange. Later that day, an ash plume at an altitude of at least 10.7 km (35,000 ft) a.s.l. was detected on satellite imagery drifting SSW. The Volcano Alert Level was raised to Warning and the Aviation Color Code was raised to Red. Reports from a marine vessel in the area indicated ashfall and tephra up to pebble size, spectacular lightning, and total darkness for a little over 2 hours. Three major explosive eruptions produced ash plumes that rose to an altitude of 13.7 km (45,000 ft) a.s.l.

Ash emissions became continuous on 8 August following the last explosive event; an ash plume drifted for more than 950 km in a counterclockwise spiral at altitudes of about 9.1-13.7 km (30,000-45,000 ft) a.s.l. Seismicity decreased, although remained elevated, and ash emissions became less frequent. During 8-9 August, seismicity decreased to a level undetectable by stations on Great Sitkin, about 40 km W. On 9 August ash plumes were detected on satellite imagery early in the day; clouds prevented views during the rest of the day. The Volcano Alert Level was lowered to Watch and the Aviation Color Code to Orange. The ash plume from the third eruption on 7 August was seen on satellite imagery 1,850 km ESE of the volcano and was elongated NE-SW over 1,200 km.

According to news articles, flights from Alaska to several west coast cities were cancelled on 10 and 11 August. During 10-12 August, AVO reported that seismicity remained low, but detectable by the network on Great Sitkin.

Sources: US Geological Survey Alaska Volcano Observatory (AVO), The Seattle Times Company


Summary of eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
2008 Aug 7 2008 Aug 9 (?) Confirmed 4 Historical Observations
[ 1899 (?) ] [ Unknown ] Uncertain    
[ 1828 ] [ Unknown ] Uncertain    
[ 1827 ] [ Unknown ] Uncertain    
1760 Unknown Confirmed 0 Historical Observations

The following references are the sources used for data regarding this volcano. References are linked directly to our volcano data file. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title. Additional discussion of data sources can be found under Volcano Data Criteria.

Coats R R, 1956c. Reconnaissance geology of some western Aleutian islands, Alaska.. U S Geol Surv Bull, 1028-E: 83-100.

IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..

Miller T P, McGimsey R G, Richter D H, Riehle J R, Nye C J, Yount M E, Dumoulin J A, 1998. Catalogue of the historically active volcanoes of Alaska. U S Geol Surv Open-File Rpt, 98-582: 1-104.

Motyka R J, Liss S A, Nye C J, Moorman M A, 1993. Geothermal resources of the Aleutian arc. Alaska Div Geol Geophys Surv, Prof Rpt, no 114, 17 p and 4 map sheets.

Smith R L, Shaw H R, Luedke R G, Russell S L, 1978. Comprehensive tables giving physical data and thermal energy estimates for young igneous systems of the United States. U S Geol Surv Open-File Rpt, 78-925: 1-25.

Wood C A, Kienle J (eds), 1990. Volcanoes of North America. Cambridge, England: Cambridge Univ Press, 354 p.

Located at the northern end of a shallow submarine ridge trending perpendicular to the Aleutian arc, Kasatochi is small 2.7 x 3.3 km wide island volcano with a dramatic 750-m-wide summit crater lake. The summit of Kasatochi reaches only 314 m above sea level, and the lake surface lies less than about 60 m above the sea. A lava dome is located on the NW flank at about 150 m elevation. The asymmetrical island is steeper on the northern side than the southern, and the volcano's crater lies north of the center of the island. Reports of activity from the heavily eroded Koniuji volcano to the east probably refer to eruptions from Kasatochi. A lava flow may have been emplaced during the first historical eruption in 1760. A major explosive eruption in 2008 produced pyroclastic flows and surges that swept into the sea, extending the island's shoreline.