Kasatochi Island
Encyclopedia
Kasatochi Island also known as Kasatochi volcano is an active stratovolcano
and one of the Andreanof Islands
subgroup of the Aleutian Islands of southwestern Alaska
, USA.
and east of Great Sitkin Island
. Kasatochi Island has a land area of 1.9503 sq mi (5.051 km²) and is unpopulated.
as Aviation Alert Level
UNASSIGNED Volcanic-alert Level
UNASSIGNED.
The summit is truncated by a large volcanic crater
containing a 0.5 mile (0.80467 km) wide crater lake
, which was formed after a large, explosive eruption perhaps only a few hundred years ago. The surface of the saltwater
lake is less than 200 ft (61 m) above sea level. Recent pictures of the volcano show that the crater lake is still present after the 2008 eruption.
. Prior to 2008, the last confirmed activity at Kasatochi was in 1899, but that was not believed to be an eruption. Mild degassing was reported to the AVO in 2005, but that could not be confirmed.http://www.avo.alaska.edu/volcanoes/volcact.php?volcname=Kasatochi
Currently, there are no seismographs or web cameras on the island of Kasatochi, so scientists must rely on data from nearby Great Sitkin volcano
and Adak Island (near Mount Adagdak
) to obtain ongoing information on Kasatochi.
"Fortunately, the existing seismic networks on nearby volcanoes picked up the activity at Kasatochi volcano," said Tom Murray, scientist-in-charge of the Alaska Volcano Observatory (AVO). "They were installed with funding from the Federal Aviation Administration to reduce the hazard to aviation from volcanic ash. These networks were crucial in recognizing that this volcano had entered the first stage of a major eruption."
"Our hope is to have monitoring equipment on all volcanoes that pose the greatest threats to public safety," said USGS volcano scientist Marianne Guffanti. "Satellite imagery is useful to see the big picture of what is happening and what is going into the atmosphere. But direct instrumentation, such as placing seismic monitors around a volcano, will help give an early warning and give people more time to plan for hazardous events."
On October 30, 2008, the AVO lowered the alert level of Kasatochi to "UNASSIGNED", saying "Over the past 2 months, seismic activity detected on regional networks in the vicinity of Kasatochi Volcano has steadily declined in intensity. Overflights and satellite imagery show no indication of significant continuing unrest. The likelihood of resumed eruptive activity at Kasatochi has greatly diminished, therefore, we are reducing the Aviation Color Code to UNASSIGNED and Volcanic Alert Level to UNASSIGNED." http://www.avo.alaska.edu/activity/Kasatochi.php
Kasatochi also supported a colony of about 250,000 Least Auklet
s and Crested Auklet
s. This large bird colony attracted also several avian predators such as peregrine falcon
s and bald eagle
s.
After the 2008 eruption the life on Kasatochi appears to have been destroyed. A research project was started in 2009 in order to study ecosystem impact and long-term recovery.
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...
and one of the Andreanof Islands
Andreanof Islands
The Andreanof Islands are a group of islands in the Aleutian Islands in southwest Alaska. They are located between Amchitka Pass and the Rat Islands group to the west, and Amukta Pass and the Islands of Four Mountains group to the east, at about 52° North and 172°57' to 179°09' West. The islands...
subgroup of the Aleutian Islands of southwestern Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
, USA.
Geography
It lies at the Atka Pass northwest of the western tip of Atka IslandAtka Island
Atka Island is the largest island in the Andreanof Islands of the Aleutian Islands of Alaska. The island is east of Adak Island. It is long and wide with a land area of , making it the 22nd largest island in the United States. The northeast of Atka Island contains the Korovin volcano which...
and east of Great Sitkin Island
Great Sitkin Island
Great Sitkin Island is a volcanic island in the Andreanof Islands of the Aleutian Islands of Alaska. The island covers a total area of and lies slightly north of a group islands which are located between Adak Island and Atka Island....
. Kasatochi Island has a land area of 1.9503 sq mi (5.051 km²) and is unpopulated.
Volcanism
The volcano is currently rated by the Alaska Volcano ObservatoryAlaska Volcano Observatory
The Alaska Volcano Observatory is a joint program of the United States Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the State of Alaska Division of Geological and Geophysical Surveys...
as Aviation Alert Level
Volcano warning schemes
- USGS Volcano Warning Scheme for the United States :The United States Geological Survey has adopted a common system nationwide for characterizing the level of unrest and eruptive activity at volcanoes...
UNASSIGNED Volcanic-alert Level
Volcano warning schemes
- USGS Volcano Warning Scheme for the United States :The United States Geological Survey has adopted a common system nationwide for characterizing the level of unrest and eruptive activity at volcanoes...
UNASSIGNED.
The summit is truncated by a large volcanic crater
Volcanic crater
A volcanic crater is a circular depression in the ground caused by volcanic activity. It is typically a basin, circular in form within which occurs a vent from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of great depth...
containing a 0.5 mile (0.80467 km) wide crater lake
Crater lake
A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not...
, which was formed after a large, explosive eruption perhaps only a few hundred years ago. The surface of the saltwater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
lake is less than 200 ft (61 m) above sea level. Recent pictures of the volcano show that the crater lake is still present after the 2008 eruption.
August 2008 eruption
On August 7, 2008, Kasatochi began erupting explosively with an ash plume maintaining an altitude of 35,000 feet and reaching 45,000 feet. As the eruption became imminent, it forced two biologists from the U.S. Fish and Wildlife Service to evacuate the island. An ashfall advisory was issued at the time for Adak IslandAdak Island
Adak Island is an island near the western extent of the Andreanof Islands group of the Aleutian Islands in Alaska. Alaska's southernmost town, Adak, is located on the island...
. Prior to 2008, the last confirmed activity at Kasatochi was in 1899, but that was not believed to be an eruption. Mild degassing was reported to the AVO in 2005, but that could not be confirmed.http://www.avo.alaska.edu/volcanoes/volcact.php?volcname=Kasatochi
Currently, there are no seismographs or web cameras on the island of Kasatochi, so scientists must rely on data from nearby Great Sitkin volcano
Great Sitkin Island
Great Sitkin Island is a volcanic island in the Andreanof Islands of the Aleutian Islands of Alaska. The island covers a total area of and lies slightly north of a group islands which are located between Adak Island and Atka Island....
and Adak Island (near Mount Adagdak
Mount Adagdak
Mount Adagdak is a Pleistocene age stratovolcano on the northernmost extremity of Adak Island in the Aleutian Islands, Alaska. Located about from Anchorage, the mountain is located about south of Cape Adagdak, for which it was named in 1948 by the United States Geological Survey.John Hunter of...
) to obtain ongoing information on Kasatochi.
"Fortunately, the existing seismic networks on nearby volcanoes picked up the activity at Kasatochi volcano," said Tom Murray, scientist-in-charge of the Alaska Volcano Observatory (AVO). "They were installed with funding from the Federal Aviation Administration to reduce the hazard to aviation from volcanic ash. These networks were crucial in recognizing that this volcano had entered the first stage of a major eruption."
"Our hope is to have monitoring equipment on all volcanoes that pose the greatest threats to public safety," said USGS volcano scientist Marianne Guffanti. "Satellite imagery is useful to see the big picture of what is happening and what is going into the atmosphere. But direct instrumentation, such as placing seismic monitors around a volcano, will help give an early warning and give people more time to plan for hazardous events."
On October 30, 2008, the AVO lowered the alert level of Kasatochi to "UNASSIGNED", saying "Over the past 2 months, seismic activity detected on regional networks in the vicinity of Kasatochi Volcano has steadily declined in intensity. Overflights and satellite imagery show no indication of significant continuing unrest. The likelihood of resumed eruptive activity at Kasatochi has greatly diminished, therefore, we are reducing the Aviation Color Code to UNASSIGNED and Volcanic Alert Level to UNASSIGNED." http://www.avo.alaska.edu/activity/Kasatochi.php
Biology
Prior to the 2008 eruption, a Steller Sea Lion rookery was on the north half of the island.Kasatochi also supported a colony of about 250,000 Least Auklet
Least Auklet
The Least Auklet, Aethia pusilla, is a seabird and the smallest species of auk. It is the most abundant seabird in North America, and one of the most abundant in the world, with a population of around nine million birds. They breed on the islands of Alaska and Siberia, and spend the winter close to...
s and Crested Auklet
Crested Auklet
The Crested Auklet is a small seabird of the family Alcidae which nests in huge colonies in the Bering Sea and Sea of Okhotsk. They often breed in mixed-species colonies with Least Auklets, their smaller congener.The Crested Auklet can measure in length, in wingspan and weigh...
s. This large bird colony attracted also several avian predators such as peregrine falcon
Peregrine Falcon
The Peregrine Falcon , also known as the Peregrine, and historically as the Duck Hawk in North America, is a widespread bird of prey in the family Falconidae. A large, crow-sized falcon, it has a blue-gray back, barred white underparts, and a black head and "moustache"...
s and bald eagle
Bald Eagle
The Bald Eagle is a bird of prey found in North America. It is the national bird and symbol of the United States of America. This sea eagle has two known sub-species and forms a species pair with the White-tailed Eagle...
s.
After the 2008 eruption the life on Kasatochi appears to have been destroyed. A research project was started in 2009 in order to study ecosystem impact and long-term recovery.
External links
- USGS: Kasatochi volcano
- Kasatochi Island Photos Photos from Kasatochi Island, July 2008
- Alaska Volcano Observatory, Kasatochi Description and Statistics