Kasatochi Island (Aleut: Qanan-tanax̂; Russian: Касаточий остров), also known as Kasatochi volcano, is an active stratovolcano and part of the Andreanof Islands subgroup of the Aleutian Islands of southwestern Alaska. On 7 August 2008, Kasatochi began erupting explosively with an ash plume reaching 45,000 feet (14,000 m). The eruption lasted for 24 hours and destroyed most life on the island. Since the eruption, it has been the site of research on the primary succession of species back onto the island. It currently does not support any consistent human population.
Kasatochi Island is a member of the Aleutian Islands, which lie above a narrow ridge that separates the Bering Sea from the North Pacific. It lies at the Atka Pass northwest of the western tip of Atka Island and east of Great Sitkin Island. It is at 52.177° N latitude and 175.508° W longitude, with a summit elevation of 314 m (1030 ft.) It has a land area of 1.9503 sq mi (5.051 km2).
Pre-2008 ecology
Geology Kasatochi Island has a unique landscape that makes it an ideal home for many types of species. Some of these aspects that created such a beneficial habitat reflected strictly on the island's geology. Before 2008, the island was about 3 km in diameter and stood about 314 m high on the highest side. The island is steeper to the northern side than the southern side, and slightly north of the center of the island is a steep-walled caldera surrounding a lake. The crater is about 4,000 feet (1,200 m) in diameter, with its lake's surface lying only about 60 m above sea level. In all areas surrounding the crater, the island is characterized by steep sea-cliffs, talus slopes, and small, boulder-filled beaches. These many habitat possibilities set the stage for the numerous species that took residence there.
Flora Before the 2008 eruption, the Kasatochi Island landscape was steep and rugged, home to dense vegetation and different species of flora. Except crater walls and sea-cliffs, nearly the entire island was vegetated with grasses and herbaceous plants. This terrestrial vegetation created the habitat for many of the species unique to Kasatochi Island. The coastal and marine habitat flourished with their own species of vegetation as well, including many different types of sea grasses, kelp, corals, sponges, and roots (namely along the rocky coasts).
Fauna Kasatochi Island was the home of many species, but most notable were the populations of diverse seabirds, avian predators and marine invertebrates. Ocean currents, productivity, and the habitable island geology created the ideal conditions for these select groups of fauna. The island differentiated itself from many of the others in the Aleutian chain by supporting a large diverse group of seabirds, most famously for their colony of more than 100,000 crested auklets and 150,000 least auklets, which was one of only seven colonies in the Aleutian chain. Other species included seabirds such as the Fork-tailed petrel, the whiskered auklet, the ancient murrelet, gulls, guillemots, and cormorants. These seabirds attracted many avian predators as well, such as bald eagles and peregrine falcons. The birds of Kasatochi were the dominant vertebrates on the island and the most prominent link between the terrestrial and marine ecosystems. Many other species were on the island, including various insects, arthropods, and fish. The abundance of fish and various marine life helped support the massive influx of auklets to the island every year. It was also noted for the presence of an endangered Steller sea lion rookery on the north half of the island. Near-shore benches were carved out of lava flows that could have been dated up to hundreds of years earlier. Approximately 1000 Steller sea lions occupied these rookeries before the 2008 eruption.
August 2008 eruption Before 2008, little was known about the eruptive history or probability of future eruptions on Kasatochi Island. There were no monitoring devices on the island, but devices on two nearby islands had indicated detectable seismic activity on Kasatochi for several years. Because of the lack of necessary technology, predicting the following eruption would have been an extremely unlikely feat. Thus, it happened quite rapidly and without much warning. On 7 August 2008, Kasatochi began erupting explosively with an ash plume maintaining an altitude of 35,000 feet and reaching 45,000 feet. The eruption lasted for 24 hours and included "two initial explosive pulses and pauses over a 6-hr period that produced ash-poor eruption clouds, a 10-hr period of continuous ash-rich emissions initiated by an explosive pulse and punctuated by two others, and a final 8-hr period of waning ash emissions." Pyroclastic flows continuously fell over the island and buried most of it in deposits ranging from decimeters to tens of meters. Before the 2008 eruption, there had been little documented activity on the island. The last confirmed activity on 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. A significant number of people were affected by the 2008 eruption, from the eruption and its secondary consequences. As the eruption became imminent, it forced the only humans on the island, two biologists from the U.S. Fish and Wildlife Service, to evacuate. Their research was stopped and later replaced with the research currently ongoing on the island. There were also nearby islands that were affected by the eruption. An ashfall advisory was issued at the time for Adak Island, a populated island in the Aleutian chain. Later, up to 6 cm of ash was found on Adak and other neighboring islands, the rest falling into the surrounding sea. At the time there were about 300 people living on the island, and while there were no immediate deaths or injuries, the long-term effects of this population being so close to the eruption are still unknown.
Post-2008 ecology
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