Page 94 - 2008 DT 12 issues

Ice they hold about 80% of Earth’s (the Matterhorn), and large rounded
fresh water. boulders that form as the glacier
hose of us who live in the Enduring ice is most common drags and grinds down the bedrock
Mojave Desert are most likely at the poles. The Antarctic ice sheet over which it flows. Transported
Tto think of ice as something to covers 5 million square miles and is material erodes from the glacier
keep our drinks cold. We almost never over 14,000 feet thick. Its sheer weight and is deposited in outwash plains.
see road ice unless we’re driving up has depressed the continent below sea Sometimes, huge blocks of ice are
the higher slopes of Mt. Charleston in level in many areas. If melting were left behind by a retreating glacier.
winter. Ice in just the right amounts, to occur, the continent would slowly Glacial lakes formed by ice
however, is vital to life on Earth . . . rise and readjust itself, just as the dams can blow out, cascading down in
and it’s disappearing. continent of Europe is rising after the torrential floods. Water running under
Although evidence for the last ice age. Both the Antarctic ice a glacier will erode channels. The
earliest ice age dates to about 2.3 sheet and the smaller Greenland ice resulting sediment deposits remain
million years ago, the Pleistocene sheet are flowing downslope . . . and as winding ridges called eskers, often
Epoch is commonly known as “The are shrinking. As these sheets slowly up to 100 ft high. Drumlins, clusters
Ice Age,” when ice covered about 30 move, faster outlet glaciers embedded of elongated hills made of till, form
percent of the Earth. It lasted from in the flow break into icebergs once in a parallel line in the direction
about 1.8 million to 11,000 years of movement near the margins of
ago. At least 20 times during this retreating ice sheet.
Epoch, ice sheets have intermittently The size, growth and life span of
advanced and retreated. Between 1.8 a glacier depends upon climate. The
and 1.0 million years ago, a cycle World Glacial Monitoring Service
of glacial advance and melting took studies glaciers, measuring their
about 40,000 years to complete. mass balance to determine whether
During much of the last million years, they are advancing or retreating.
however, the cycle has taken longer— From 1980 to 2004, it monitored 30
approximately 100,000 years. The glaciers in nine mountain ranges,
most recent “icing” in North America, including ranges in North and South
known as the Wisconsin glaciation, America, Europe and Asia. The
began about 115,000 years ago and data indicated that the mean mass
ended with the start of the modern balance of those glaciers has been
Holocene Epoch 11,000 years before continuously negative since 1990.
the present. they reach the ocean. It was one Since 1979, the size of the
Glaciers are complex systems of these that sealed the fate of the summer polar ice cap has also shrunk,
that currently cover about 10% of the Titanic. by more than 20 percent. The world
Glaciers wax and wane on a wide retreat of the ice is believed to
Earth’s surface. They consist of ice, seasonal basis, and also in response to be caused by global warming. The
snow, water, rock and sediment that long term climate change. In summer, trend began as early as the Industrial
slowly move by the force of gravity. the upper layers of snow thaw, Revolution when humans began
Glaciers form where the temperature producing meltwater. In winter, snow to use fossil fuels, which cause the
is cold enough to let falling snow accumulation rebuilds the layers and atmosphere to warm through the
accumulate and transform into ice. so, with no mass loss or gain, the production of greenhouse gasses.
They fall into several categories glacier remains in equilibrium. Natural causes are thought by some
by size (ice sheets, ice caps or ice Glaciers shape the landscape. scientists to be playing an important
fields) and location (valley, Alpine They are responsible for features role in today’s warming trend as well,
and Piedmont glaciers). All together, such as fiords in coastal areas, horns as they have in past Epochs.

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