Re: Volcano Eruption - Alaska
Source:
http://www.adn.com/aleutians/story/551527.html
Volcanic eruption leaves nothing but ash behind
Scientists escaped Kasatochi; plants, birds, animals didn't
By GEORGE BRYSON
gbryson@adn.com
Published: October 10th, 2008 02:56 AM
Last Modified: October 10th, 2008 05:05 AM
The surprise eruption of Kasatochi Volcano in the central Aleutians this summer turned a small green island rich with seabirds and ocean mammals into a sterile gray lump, scientists say.
ens of thousands of fledgling auklets and petrels perished in their rocky nests, as Kasatochi erupted for the first time in centuries, smothering under a deep blanket of ash anything that couldn't flee.
"Probably 20 percent of auklet chicks were still in their crevices and hadn't left," said Jeff Williams, a Homer-based biologist with the U.S. Fish and Wildlife Service. "They were most likely entombed."
A couple hundred adult sea lions still encircle the island, but all the year's pups have disappeared, Williams said.
As for the bird habitat?
"It's gone pretty much completely," said Williams, who's spent 18 years observing bird populations on Kasatochi, a tiny island near Atka in the Alaska Maritime National Wildlife Refuge. Since its eruption on Aug. 7, Williams and other biologists have returned to examine the damage.
Kasatochi's only structure, a 1930s-era trapper's cabin, is nowhere to be seen. Ash heaps next to cliffsides rise 100 feet high. The island has grown larger, Williams said. The cove where he and other federal biologists used to anchor their boat in seawater 60 feet deep is now solid ground. An almost featureless, ashy mud coats the island.
"So basically it's an almost sterile, start-from-scratch sort of thing."
For a few scientists, that raises an intriguing question: How soon will life return to Kasatochi?
Williams is anxious to find out.
So is Alaska Volcano Observatory geologist Christina Neal, who tracked the near-simultaneous eruptions this summer of Kasatochi and two other Aleutian peaks -- Okmok Volcano and Mount Cleveland.
"We might learn something important about how ecosystems evolve on fresh volcanic surfaces," Neal said. "The eruptions were terribly exciting, and we all worked very hard, but now the more careful science begins."
NESTING PARADISE
Like other tall, conical "stratovolcanoes" in the Aleutian arc, which comprises 40 active volcanoes, Kasatochi emerged from the sea by exploding on itself again and again through geologic time. It just hadn't done so lately.
Volcanologists say Kasatochi possibly erupted in 1760, then stirred again without erupting in 1899. Since then, however, it's hardly made a noise.
When the celebrated biologist Olaus Murie traveled to Kasatochi on behalf of the U.S. Biological Survey in the 1930s, he found a green, steep-sided island two miles square writhing with tufted puffins -- and hardly a terrestrial predator in sight. At least not any indigenous species.
That's because carnivorous terrestrial mammals are not native to the Aleutian Islands west of Umnak Island, said Williams, who's written papers on the islands' natural history.
Just prior to Murie's arrival, however, fur-ranchers had introduced arctic fox to the island. Only a few were present when he arrived, but eventually the effect was disastrous. Darting from nest to nest, the fox made out like bandits, and all the ground-breeding auklets and puffins soon disappeared.
"They were just sitting birds," said Williams.
In the 1980s, biologists with the Fish and Wildlife Service (successor to the Biological Survey) returned to Kasatochi and found one of the densest populations of foxes in the Aleutians -- and no rock- or burrow-nesting seabirds at all. So the refuge administrators decided to eliminate all the foxes. In a couple of seasons they succeeded.
Since the 1990s, government biologists have been closely monitoring Kasatochi's recovery. Until this summer it was doing great, Williams said. The island had built up strong numbers of several species of seabirds.
"There were hundreds of thousands of these auklets that nest on the island ... and thousands of birds like petrels, puffins and small songbirds. There were falcons, eagles and small shorebirds called oystercatchers. There were harbor seals ... and hundreds of sea lions."
BURIED IN ASH
On Aug. 7, Kasatochi began to vibrate with the first of three powerful eruptions, and all that soon disappeared. The volcano shot an ash cloud eight miles high. Two biologists on the island narrowly escaped in a boat.
The small emerald-green lake that moments earlier had perched at the top of the Kasatochi crater may have been a factor in the ferocity of the blast -- as hot magma made contact with the cold water, Neal said.
"It's just like throwing water on rocks in the sauna," she said. "You get a tremendous flashing of water into steam. And what happens is the magma gets fragmented into very tiny pieces of ash."
In a few days, the Kasatochi ash plume forced Alaska Airlines to cancel 44 flights, and 6,000 travelers were stranded in Anchorage.
Eventually the cloud would circle the globe several times, Neal said. She was visiting Iceland later in August when the Kasatochi ash plume contributed to "a very lovely orange moonrise one night."
Since the eruption, Williams has visited Kasatochi four times -- at a safe distance. Three times by motoring around it in a boat and once in a helicopter fly-by.
Where once there were vertical cliffs now he finds only gently sloping hillsides, and the island's coastline now extends a couple hundred yards farther out to sea, Williams said. The old sea lion rookeries are about 50 feet deep in ash.
"I would say there were about 350 (sea lions) seen earlier in the year, with lots of pups, and we saw about 160 to 180 adults and no pups at all in late August."
It's possible the pups are safe somewhere else, Williams said.
"Of course sea lions can swim away. Birds can fly away. It's just a matter of dead babies, or whether (the parent birds) were too stubborn and obstinate to leave."
WATCHING LIFE RETURN
Now scientists are being drawn to Kasatochi to see what happens next. Williams wants to document the return of all that life.
Before the island will be ready for any rock-nesting seabirds, however, the landscape will have to improve. Right now there is no vegetation, and the boulders and crevices are gone.
The eroding effect of a winter of rain and snow will help, along with the Aleutians' powerful ocean currents, which have already begun to flush away some of the new shoreline, Williams said. As birds return their feathers will bring seeds, and their droppings will help fertilize the sprouts.
"It's actually kind of a circle, because in a lot of cases the vegetation comes here because of the birds," Williams said. "They encourage the development of certain vegetation."
He's seen something similar before. Sixteen years ago a volcano erupted on tiny Bogoslof Island about 40 miles west of Unalaska. A year after the eruption, he visited the island during the summer and birds had already returned, nesting on ground still warm to the touch.
"There were birds that couldn't dig in that far because it was just so new," he said. "It was hot still and they didn't hardly have to incubate the eggs, because they were being incubated by the heat off the ground."
Neal would like to visit Kasatochi too, while it still looks raw. "All the snowmelt next spring will drastically change things," she said.
It's possible that plants that survived beneath the ash in the form of roots and rhizomes could burst forth next summer, Williams said. A few birds might show up too. But it will take time for Kasatochi to fully regenerate.
Said Williams: "It's going to be on the order of decades."
