Федеральное государственное бюджетное учреждение науки
Геологический институт им. Н.Л. Добрецова
Сибирского Отделения Российской академии наук
(ГИН СО РАН)
Мир Бурятия "Гравитация науки: Геологический институт БНЦ СО РАН"
Дайджест мировых новостей:
An island's rebirth: Life emerges after a catastrophic volcanic eruption [2010-08-25] Anchorage, Alaska mdash; A secluded island in the Aleutian chain is revealing secrets of how land and marine ecosystems react to and recover from a catastrophic volcanic eruption that appeared at first glance to destroy all life on the island.
Yet little by little ndash; a wingless beetle here, a tuft of grass there, Kasatochi, an island in the Alaska Maritime National Wildlife Refuge rarely studied by scientists before its Aug. 7, 2008, volcanic eruption, is showing signs of recovery.
In the summer of 2009, scientists with the U.S. Geological Survey, U.S. Fish and Wildlife Service, and the University of Alaska Museum of the North returned to the island to begin long-term studies to better understand the effects of the eruption and how quickly the island rsquo;s ecosystems recover.
Kasatochi volcano, Alaska, after its eruption on Aug. 7, 2008. Picture taken at 17,000 feet above seal level. Picture courtesy of Jerry Morris.
Summit crater and crater lake of Kasatochi volcano, August 6, 2008, the day before the eruption. The crater shown here is about 4,000 feet in diameter. Photo by Chris Ford, USFWS.
Despite the frequency of volcanic eruptions in Alaska, this is one of the first studies of its kind in the remote Aleutian Islands. Their findings are detailed in a series of 10 reports published in the August 2010 issue of the journal Arctic, Antarctic, and Alpine Research.
Prior to the eruption, Kasatochi was one of the most picturesque of the Aleutian Islands. nbsp; Its steep slopes were covered with low-growing grasses and wildflowers, and in the center of the island there was a steep-walled crater filled at the bottom with a small turquoise lake.
Kasatochi Island hosted a colony of about 250,000 least and crested auklets, making it one of the major seabird breeding colonies in the Aleutian Islands. In turn, the numerous seabirds attracted avian predators such as bald eagles, peregrine falcons and ravens. Kasatochi Island was also home to a rookery of endangered Steller sea lions.
But after the eruption, other than sea lions loafing on a newly formed beach, the island appeared to be completely devoid of life. The entire island and neighboring seafloor were covered with thick layers of volcanic ash and deposits from the eruption. nbsp;
That first summer after the eruption, teams of geologists, botanists, entomologists, ornithologists and marine ecologists visited Kasatochi and nearby islands four times to document the effects of the eruption and establish a baseline with which long-term observations will be compared. The team also set up sampling plots and equipment such as seismometers, time-lapse cameras and bird song recorders.
nbsp; ldquo;When we first landed on the island, we were unsure of what we would find, rdquo; said project manager Tony DeGange of the USGS. ldquo;The formerly lush, green island was uniformly gray and in the 10 months since the eruption, considerable erosion of volcanic ash had occurred. rdquo; nbsp;
By late summer, the team found several kinds of green plants scattered around the island.
ldquo;Even more exciting was the discovery of one small remnant plant community, rdquo; said USGS research geneticist Sandra Talbot. ldquo;Most of the plants likely originated from underground root systems, rhizomes or seed banks that survived the eruption, particularly in areas that were protected from the hot volcanic flows and where the ash eroded off quickly to expose the pre-eruption soils. rdquo;
Entomologist Derek Sikes from the University of Alaska Museum of the North also discovered that terrestrial arthropods had survived the eruption. He found wingless carrion beetles, a centipede and a spider, as well as kelp flies and a blowfly that were eating bird carcasses and kelp that had washed up on the island.
Thousands of seabirds returned to the island that first summer, although none nested successfully, according to Jeff Williams of the U.S. Fish and Wildlife Service rsquo;s Alaska Maritime National Wildlife Refuge.
ldquo;The auklet colony was buried under volcanic debris and ash, rdquo; Williams said. ldquo;They were unable to locate suitable nesting crevices and laid eggs on the ground or in the water instead. It will be interesting to see if erosion eventually exposes the rock crevices that these birds need for nesting or if they eventually abandon the island. Steller sea lions, rdquo; he added, ldquo;were the only wildlife species to breed successfully. rdquo;
Similar to what the research team found onshore, nearshore habitats were blanketed with sediments and were largely devoid of life. Most of the kelp forests in the ocean around the island had been covered with volcanic debris.
ldquo;We are now in the midst of our second year of research at Kasatochi Island, and our intent is to continue this work for many years, rdquo; said DeGange. ldquo;The Aleutian Islands are a part of the Pacific ring of fire, and destructive volcanic eruptions are a primary form of ecosystem disturbance in these earthquake- and volcano-prone zones that reach from Chile up to Alaska and down through the South Pacific. Kasatochi Island is a natural laboratory that will help us understand how volcanic eruptions shape Aleutian Island ecosystems. rdquo;
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