Stories tagged antarctica

Mar
25
2008

Ice capade: Aerial views of the ice sheet breaking at the Wilkins Ice Sheet in Antarctica show the massive amount of ice that's come free in the past month.
Ice capade: Aerial views of the ice sheet breaking at the Wilkins Ice Sheet in Antarctica show the massive amount of ice that's come free in the past month.Courtesy National Snow and Ice Data Center/NASA
So we’ve been grumbling the past few days about the latest round of snow and ice that’s descended upon us in the early days of spring. At least we’re a long way from Antarctica.

The National Snow and Ice Center today reported, and released photos, of a huge ice sheet collapse from the cold continent. About 160-square miles of ice have broken free from the Wilkins ice sheet since Feb. 28 in some major league size pieces. While the Wilkins ice sheet is about the size of Connecticut, one large portion of broken ice sheet is seven times larger than the Manhattan district of New York City.

While that’s a big chuck of ice to break free, larger ice collapses have happened two other times since scientists have been monitoring the site: in 1995 and 2002. Yet, the experts are saying that this latest ice break is another sign of global climate change.

Other portions of the ice shelf are hanging on by thin margins and one expert predicts that the entire shelf could be gone in 15 years. Cracks in the thin ice fill with water, which accelerates the melting, and leads to more major ice breaks.

Here's a link to some great video of the fragile ice sheet area from National Geographic.

Feb
25
2008

A sea spider. Deal with it.: And this one's not even giant.
A sea spider. Deal with it.: And this one's not even giant.Courtesy NOAA
Have y’all heard about the dang sea spiders? The giant, antarctic ones? Of course you have--you’re Buzzketeers, and, hence, are all over this Internet.

Not me. I’m not really into the Internet. Scrapbooking? Yes, I’m into that. Gin Rummy? Yes, that too. Sharing my feelings? God, yes. But the Internet not so much. Plus, I just moved, and I don’t have internet at my new home yet. I’m not actually sure that Internet even exists in West Saint Paul (I think they have to pipe it in, or ship it in trucks).

At any rate, apparently “giant sea spiders” are all the rage these days, and I had no idea. It’s frustrating, partly because it’s in my professional interest to know what’s going on with strange new creatures, and partly because I feel that the lives of these giant sea spiders must mirror my own so much--pale, slender-limbed things living in the dark. I can relate.

Sea spiders themselves are nothing new. People have known about them for hundreds of years, and, in fact, have existed since at least the Devonian Period, a hot, sticky mess of a time, full of leggy fish and 30-foot-tall mushrooms, about a hundred million years before dinosaurs even thought about existing. Sea spiders are arthropods, but not technically spiders. They can have four to six pairs of long, wormy legs, a tiny body, and a proboscis that “allows them to suck nutrients from soft-bodied invertebrates.” An enviable skill, that.

The giant sea spiders were found during an Australian scientific survey of the Antarctic sea floor, are attracting some extra attention, I suppose, because they are, you know, giant. Giant, obviously, being a relative term. The “giant” sea spiders are a foot or more across, so, you know, you still wouldn’t want one in the tub with you (or maybe you would - check out the video and decide for yourself), but it’s not like they could destroy Tokyo, or anything.

Along with the “spiders” the census revealed dozens of bizarre deep-sea creatures, many of which had never before been catalogued. The expedition was also part of an effort to monitor the sea floor (over 1000 meters below the surface in this case) as it undergoes environmental change. Rising carbon levels, for instance, will make the water more acidic, and will hinder the growth of coral and creatures with calcium carbonate skeletons.

As it happens, the sea spiders have non-calcareous exoskeletons, which is lucky for them, but contributes to my general reaction to their existence: they’re weird, and they make me uncomfortable. I don’t trust them. Invertebrates have been separated from us chordates for so long... there’s just no telling what could be going through their heads at any given time. And when you consider something like giant sea spiders, living at the bottom of an icy Antarctic sea, just... squirming around. It almost too much to bear. They’re probably into the weirdest things. And if you accept that arthropods are bad, well, don’t even get me started on molluscs--squid and cuttlefish with their fancy brains, they just give me the willies. I’ll do a Buzz post on them someday.

Jun
04
2006


Meteor Crater near Winslow, AZ: This crater formed when a meteor collided with Earth about 50,000 years ago. It is approximately 3/4 mile in diameter and 650 feet deep.
Courtesy Mark Ryan

A 300 mile wide crater (bigger than Ohio) has been detected beneath a half-mile of ice in Anartica. This crater is twice as big as the one thought to have killed the dinosaurs. Reseachers believe the impact may have broken up the Gondwana supercontinent, pushing what is now Australia northward.

Two separate data sets were combined to understand more about this impact. Radar to detect a crater, and gravity measurements to detect a mass concentration, or "mascon" in the same place. When a large mass slams into the earth, there is a rebound of mantle material up into the earth's crust creating a bump or mascon..

"On the moon, you can look at craters, and the mascons are still there," von Frese said. "But on Earth, it's unusual to find mascons, because the planet is geologically active. The interior eventually recovers and the mascon goes away." He cited the very large and much older Vredefort crater in South Africa that must have once had a mascon, but no evidence of it can be seen now.
"Based on what we know about the geologic history of the region, this Wilkes Land mascon formed recently by geologic standards -- probably about 250 million years ago," he said. "In another half a billion years, the Wilkes Land mascon will probably disappear, too." Ralph von Frese, a professor of geological sciences at Ohio State University

The Permian-Triassic extinction about 250 million years ago, when almost all animal life on Earth died out, may have resulted from this impact.

Not all scientists agree, however

Scientists contacted by [email protected] say they are sceptical, as no signs of such an enormous impact have been found in other, well-studied areas of Antarctica. Jane Francis, a geologist at the University of Leeds says, "That sequence has been worked on before, and no one has found evidence to support a massive impact like this," Paul Wignall, a palaeontologist at the University of Leeds, UK, who studies mass-extinction events says that few scientists will be convinced by the hypothesis until the team can precisely date their crater directly, and find rocks there that have been altered by the searing heat of the explosion.

Most think that the extinction started when a vast volcanic eruption released huge amounts of gas, including sulphur dioxide and carbon dioxide, into the atmosphere, causing acid rain and greenhouse warming. Von Frese notes that the explanations aren't mutually exclusive: the shockwaves from a huge impact could have travelled through the planet to trigger the eruptions in Siberia, delivering a devastating combination of disasters.

Too much ice covers the putative crater for a drilling expedition. But Von Frese hopes to make a research trip to Antarctica to look for rocks at the base of the ice sheet along the continent's coast that could attest to an impact.

Sources:
NatureNews
physorg
space
BBCnews
Yahoo news