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Maggie Amsler
Research Assistant

KaBOOM! The birth of an island

Journal By Maggie Amsler

Posted On 3/2/2004 5:21:04 PM

It is not uncommon to hear the sound of explosions at Palmer Station. Demolition can rattle the station buildings day and night. Rather than fiery explosive charges bursting, the sound of kaboom! is generated by Mother Nature rearranging the glacier forming the back wall of Arthur Harbor.

Glaciers are giant sheets of ice, age-long accumulations of ice, water, air, and ground up rock sediment. Antarctica of course is blanketed by glaciers; in some areas the ice is 4 km ( ~2 miles) thick. Due to the sheer weight or mass of the ice, glaciers flow like water, albeit much slower. Glaciers flow in response to Mother Nature’s gravity. The ice is either shuffled around internally or karate-chopping wedges of ice off the glacier face. (The face of a glacier is the vertical wall of ice immediately in contact with land or water is rises above.)

The latter, known as calving, is a dramatic sight to the per-chance witness as that lopped off ice wedge of ice is viewed sliding, swan diving, or careening into the harbor waters with a resounding splash. A “boom” accompanies both types of glacier movement, as the ice buckles under its own weight at a stress point. Some of the booms really do rattle windows overlooking the harbor.

Calving glaciers can generate icebergs the size of small New England states. This is more typical of the ice sheets covering the continent of Antarctica proper. On Anvers Island, where Palmer is located, and other islands along the Antarctic Peninsula, calving glaciers may generate icebergs the size of multistory buildings as well as bergy bits approximating the size of a car and brash ice (the size of tractor tires down to hand-sized pieces of ice). After an active day of calving, waters surrounding the station can be referred to Arthur Harbor Slushy - the surface smothered by pieces of brash ice sprinkled with bergy bit chunks.

In the 1980’s when I first started working here (I was a precocious toddler) the harbor was in effect much smaller than it is today. The glacier took up much more room and was closer to the station during my previous seasons during the ‘80s and early ‘90s. When Dr. McClintock hired me as his research assistant in 2000 and I sailed back into Arthur Harbor in the new century, I was stunned to see how dramatically the glacier had changed during my nearly decade absence. It was like looking at a renovated house where the walls between the kitchen, dining room and living room had been removed to create a great room. Arthur Harbor as such was huge, the back walls of the glacier knocked down by Mother Nature. In the course of 10 years ‘glacial speed’ can indeed result in noticeable changes.

One of my favorite activities in spare time here is to ski on or hike up the glacier that rises above Palmer Station. Glaciers are moving sheets of ice and move not only at the face as is evidenced in the harbor but also move internally. In some areas, a portion of ice may move faster than the ice surrounding it. When this happens, cracks or crevasses in the surface are created. It is not unlike a concrete section of sidewalk buckling and cracking due to uneven temperature or moisture.

Crevasses are especially dangerous after the winter’s heavy snowfall fills in the cracks forming snowbridges. As the summer approaches and some of this snow melts, the snowbridges may no longer be able to support the weight of a person and collapse into the crevasse as an individual skis or walks on it. Crevasses vary in size and depth but unwary glacier travelers can be swallowed up by big ones and require rescue.

So at Palmer, early in the summer, specially trained folks go up and check the glacier for crevasses and flag out a safe, no-crevasse zone for recreation. Rather than “following the yellow brick road”, we stay inside the black flag topped bamboo poles stuck in the glacier.

In the past three years, one particular part of the glacier has been extremely active, both at the face of the glacier and internally. Back in my early years, it was possible for the trained glacier team to safely ski over to Norsel Point and the original Palmer Station, a short distance away as the skua flies. (See general questions for more info on Old Palmer). I think by 1992 (my last season before resuming with UAB) this was considered a risky undertaking because the area was a jumble of crevasses.

Today that trip would be impossible. Over the years the adjoining glacier face has been chopped away and just two years ago, a new small cove was created. That cove continued to deepen as the face eroded and eventually met up with what had been the crevasse field. Last June when we left for home, a small sliver of glacier still connected Anvers Island to Norsel Point. Just a few months ago those two active areas of this portion of glacier met and resulted in collapse of the connecting ice wedge. Allow me to introduce Norsel Island!


TitleFromClick here to change to descending sortDate Posted
Re: KaBOOM! The birth of an islandDee3/2/2004 7:59:48 PM

Your article on glaciers and the "birth" of Norsel Island were fascinating. Do glaciers always travel slowly in easily predictable paths? I assume the glacier was there before the current Palmer Station was build, correct? So were engineers confident the glacier would never be a threat to Palmer Station? We wouldn't want to learn you have floated away to sea as a bergy bit!

From Maggie Amsler, Posted On 3/2/2004 7:59:48 PM

Hi Dee! I am not a glaciologist but I believe the path of a glacier is governed by many factors including the composition of the underlying substrate and climatic factors that regulate the percentage of ice accumulation versus ice loss. The eroding glacier face that created Norsel Island is across the harbor from Palmer Station. The glacier immediately behind the station reached it terminus and no is longer calving. It does shift and crevasse though on either side of the flagged zone where the glacier faces meet water and continue to calve. Our station is built on solid rocky ground so there is no fear of us being set adrift on ice! Someday though we may not be able to traverse the glacier at all because of encroaching crevasse fields.

Re: KaBOOM! The birth of an islandDavianta Jackson3/3/2004 2:14:15 PM

Have you ever experienced the ice cracking or a cravass forming while you were walking or skiing on the glacier?

From Maggie Amsler, Posted On 3/3/2004 2:14:15 PM

Chilling question Davianta! I have been inside a crevasse but only by choice, not accident. The glacier rescue team was training and had hung a rope ladder into the mouth of a large, deep crevasse. The ladder was anchored into the glacier with long ice screws. As a precaution, I wore a climbing harness with a rope that was attached to the surface and could be used to pull me out if the ladder broke. I also wore a hard hat as protection against falling ice chunks. I climbed down about 10 feet into that frigid, blue chasm and was awed by the crystal clear bluish polished ice and the long, thick needle pointed icicles dripping away. It was very peaceful and warm compared to the blustery, gray day up top. It was a little eerie not being able to see the bottom and yet hear what sounded like a big river of water rushing somewhere deep beneath that last rung! This is the only way I ever hope to visit a crevasse.

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