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Glaciers sure are cool, aren’t they? (Now that I’ve got that out of my system, we can continue.) Glaciers aren’t just cool; they’re giant masses of ice that creep down mountains or cover entire continents. One such glacial variant is known as an alpine glacier, but alpine glaciers are not confined solely to the Alps--they can be found around the world. Ice sheets, another variety of glacier, are the massive domes of ice that cover Greenland and Antarctica. These frozen behemoths move slowly but inexorably, carving the land beneath them. Glaciers aren’t a purely destructive force, though--they are an important reservoir for fresh water to fill the valleys and rivers they carve out. Climate change has proven an unprecedented threat to glaciers, causing them to melt at a faster rate and leading to rising sea levels.
By analyzing questions, you can see patterns emerge, patterns that will help you answer questions. Qwiz5 is all about those patterns. In each installment of Qwiz5, we take an answer line and look at its five most common clues. Here we explore five clues that will help you answer a tossup on glaciers.
ZONE OF ABLATION & ZONE OF ACCUMULATION
The life of a glacier is a long and slow one. Glaciers are formed by dense layers of snow that accumulate each season without melting. As the snow becomes more and more compressed, it transitions first to a substance called firn and then into glacial ice. Glaciers are constantly adding to their overall mass through this process while also losing mass due to melting or sublimation. The region of a glacier where more mass is being added is known as the zone of accumulation. Conversely, certain regions of the glacier tend to lose more mass. These regions make up the zone of ablation.
ARÊTES
We can thank glaciers for some of the most arresting mountain scenery in the world. As alpine glaciers descend down a mountain they carve out a record of their path. When two adjacent glaciers erode a steep ridge into a mountain, the result is known as an arête. Three or more arêtes form a distinct, sharply-defined peak known as a horn. This glacial feature is evident on the Matterhorn, Switzerland’s appropriately-named “Mountain of Mountains” or “Great Mountain”.
BERGSCHRUNDS
A common glacial threat is a type of crevasse known as a bergschrund. These crevasses can often be over 300 feet deep and are extremely difficult for even experienced mountaineers to traverse. Bergschrunds are formed when the moving part of a glacier separates itself from stationary glacial ice. Although the terms may be used interchangeably, bergschrunds and randklufts are different phenomena. Randklufts are formed when a crevasse forms between glacial ice and a rock face.
ISOSTATIC REBOUND
Glaciers are enormously heavy--so heavy, in fact, that entire continents buckle under their weight. Following the Last Ice Age glaciers receded from much of the world. As these glaciers recede, however, the land that had been compressed underneath the glacier’s weight slowly returns to its original shape. This rising of the Earth’s crust, known as isostatic rebound, is still occurring today, although at a much slower rate.
MORAINES, ESKERS, AND DRUMLINS
Glaciers leave more behind them than just a literal impression. Moraines are essentially glacial detritus: unsorted accumulations of glacial till (rocks ground up and carried along by the glacier). When the glacier retreats, the debris remains. When these debris remain as a long, winding ridge they are known as eskers. Another notable glacial leftover is the drumlin, a long, teardrop-shaped hill of glacial sediment.
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Quizbowl is about learning, not rote memorization, so we encourage you to use this as a springboard for further reading rather than as an endpoint. Here are a few things to check out:
There are many different types of glacial landforms, and the National Snow and Ice Data Center has a handy guide to differentiating them.
Glaciers have long captivated artists, but in the future there may not be enough left to provide inspiration.
Ice isn’t just beautiful to look at; it can create some interesting sounds too. Here’s a recording of the sounds from a lake of ice, though we can’t recommend it for your workout playlist.
Calving, the process by which part of a glacier breaks off and falls into the ocean, can be a violent process, as we can see in this video:
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