Theme: Glaciers

 

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Text, Viewspace. The show will continue in 15 seconds. Coming up: Survey glaciers with NASA satellites! 

 

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The text appears on a background of stars which move slowly towards and past us. 

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An animated globe turns. Text, Almost 10 percent of Earth's land area is covered by glaciers.

 

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Yellow highlights on a world map. Text, Glaciers are found on every continent and even near the equator, although most are at higher latitudes near Earth's poles.

 

A yellow arrow points to New Zealand.

 

A yellow arrow points to Mount Cook

 

Details of Mount Cook New Zealand. Tasman Glacier, Mueller Glacier. Text, Glaciers are reservoirs that hold 75% of the world's fresh water.

 

Much of the world's population depends on the seasonal melting of glaciers for their freshwater supply.

 

1993, Mount Kilimanjaro Tanzania. The glacial melt from Mt. Kilimanjaro helps rejuvenate freshwater springs and wells that sustain the people, animals, and plants in its shadow.

 

The volcano's ice cap formed some 11,000 years ago.

 

2009. Since the 1800s, more than 90% of Kilimanjaro's glacial ice has disappeared.

 

2017. Increasing temperatures, drier air, and deforestation of the volcanoes lower slopes likely caused the rapid decline.

 

The summit will soon be completely free of glacial ice.

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Text, Myth versus reality. An ancient drawing of a ship at sea surrounded by monsters. A photo of an icy glacier landscape. Myth, Glaciers are found only at or near Earth's north and south poles.

 

Reality, Most glaciers are found at high latitudes close to Earth's poles, but they can also exist at high elevation near the equator. Glaciers exist on every continent. Although there are no glaciers in Australia, there are some in New Zealand, which is part of the Australian continent. 

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An animation of Earth in a star-filled sky. Text, at-a-GLANCE, Glaciers

 

Three basic types of glaciers are alpine glaciers, piedmont glaciers, and continental glaciers.

 

Piedmont Glacier, Malaspina Glacier, Alaska, Continental Glacier, Greenland Ice Sheet, Alpine Glacier, Aletsch Glacier, Switzerland. Alpine glaciers are streams of ice that can fill the valleys of mountainous regions.

 

Alpine Glacier, Aletsch Glacier, Switzerland. They are named for the glaciers first observed in the European Alps.

 

Alpine glaciers are nourished by snowfall high on their host mountain's flank.

 

When alpine glaciers reach the relatively flat plains below their host mountains, they can spill out onto the plains to form piedmont glaciers.

 

Piedmont Glacier, Malaspina Glacier, Alaska. Malaspina Glacier is a typical piedmont glacier. It covers more than 3,100 square miles of the Alaskan coastal plain.

 

Continental Glacier, Greenland Ice Sheet. Continental glaciers, sometimes called ice sheets, are huge masses of glacial ice that's spread radially under their own weight.

 

During the last ice age, ice sheets covered 32% of Earth's land surface, including most of North America and Scandinavia.

 

Today, only Greenland and Antarctica hold ice sheets.

 

Nearly all of the freshwater ice on Earth (99%) is locked up in the Greenland and Antarctic ice sheets.

 

The Greenland ice sheet is three times the size of Texas -- extending 656,000 square miles – and is nearly 2 miles thick near its center.

 

The Antarctic ice sheet has covered the underlined continent for the past 40 million years.

 

It flows over 5.8 million square miles and is nearly 3 miles thick in some places. Ronne Ice Shelf, Ross Ice Shelf

 

When an ice sheet extends over and floats on an ocean or sea, it is called an ice shelf.

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Text, Bering Glacier, Alaska. Bering Glacier is the largest glacier in North America.

 

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It is fed by the Bagley Icefield and terminates in Vitus Lake.

 

Higher temperatures and changes in precipitation over the past century have caused the glacier to retreat.

 

One result of the loss of glacial ice is an increase in the number of earthquakes in the region.

 

Earthquakes here occur as two tectonic plates collide, thrusting Earth's crust upward informing mountains.

 

However, the weight of glacial ice makes it harder for the crust to move.

 

As the glacier melts, that pressure is lessened.

 

The crust moves more freely, and earthquakes increase.

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Text, Glaciers; Rivers & Seas of Ice.

 

A cove of icy water flanked by two snow-capped mountains.

 

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Distinctly shaped snowflakes in free fall.

 

Text, Snow falls as beautiful, feathery, ice-crystal flakes.

 

Close up of snowflake shows a symmetrical hexagonal shape. Snow blankets the ground in mounds.

 

Text, When accumulated snow sits on the ground for a while, it may partially melt and then refreeze.

 

Islands of ice float in bright blue water. A close-up shows sharp and rugged ice crystals.

 

Text, Over time, it loses its feathery texture and becomes granular.

 

A large wall of ice topped with smooth snow.

 

After many many years of accumulation, the granules compress into ice.

 

Eventually, the ice layer becomes large enough to begin flowing under the influence of gravity.

 

Bright blue ice floats between two patches of land.

 

These flowing rivers and seas of ice are called glaciers.

 

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Planet Earth with shifting ice at the pole surrounding Greenland.

 

Text, Petermann Glacier, Greenland. July 5, 2003.

 

When a glacier extends over the ocean, the warmer water can melt and weaken the glacier.

 

An aerial view shows where ice has split into two.

 

Petermann Glacier, August 16, 2010.

 

In 2010, a large chunk broke off the floating ice "tongue" of Petermann Glacier.

 

A crack on the sheet of ice is highlighted.

 

Text, A large crevasse slicing across the glacier hinted at the potential for further breakup.

 

Text, Nearly two years later, just such a breakup occurred. Side by side of three images, July 16, 2012, 10:25 UTC, July 16, 2012, 12:00 UTC, July 17, 2012, 9:30 UTC. On each image, the same area is highlighted to show how the ice increasingly broke off.

 

Text, Petermann Glacier, Greenland. July 21, 2012. Icebergs littered the water in the ice island's wake.

 

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The continent of Antarctica.

 

Antarctica. Some of the fastest changing glaciers are in Antarctica, where ice is disappearing at a rate of more than 100 billion metric tons per year.

 

Map zooms in on northwest corner of Antarctica and the Weddell Sea.

 

Text, Larsen B Ice Shelf, Antarctica. January 31, 2002. Weddell Sea. In January 2002, the Larsen B Ice Shelf began a 35-day period of rapid disintegration, which resulted in an expanse of ice larger than Rhode Island collapsing into the Weddell Sea.

 

A series of dated images begins, February 17, 2002; February 23, 2002; March 5, 2002; March 17, 2002; and February 18, 2005. Beginning in February 2002, the shoreline rounds off as a chunk of ice falls to the sea, In March 2002, ice which floats in the black sea rejoins the shelf, and by February 2005, a larger block of ice disappears from the shoreline, leaving a more jagged ice shelf.

 

Text, Just three years later, open water lapped along the shoreline where Larsen B once stood.

 

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Crane Glacier, Antarctica. April 6, 2002. The loss of the Larsen B Ice Shelf accelerated the flow of surrounding glaciers into the bay.

 

In April 2002, two months after the ice shelf's collapse, Crane Glacier extended into the bay that once held Larsen B.

 

A time lapse shows how the shoreline of ice once fanned out and is now concaved.

 

Text, Crane Glacier, February 20, 2003. By February 2003, much of the lower Crane Glacier had crumbled into the Weddell Sea. Its fan-shaped terminus became a C-shaped cove filled with icebergs.

 

The shoreline continues to move inward while chunks of ice remain in the sea.

 

Crane Glacier, February 24, 2012. Crane Glacier continued its retreat in the following years.

 

A ship in the water next to a tall wall of ice.

 

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Text, As our planet warms, so do our oceans.

 

An ocean temperature only slightly above the freezing point of water can melt glacial ice at a rate of several feet per day, or hundreds of feet over the course of one summer.

 

Glaciers hold 75% of the world's fresh water.

 

If all land ice melted, most of it would end up in our oceans, mixing with undrinkable salt water and raising sea level by about 230 feet.

 

Such a large influx of cold, fresh water will also affect the world's ocean currents and therefore Earth's climate.

 

An animation of the north pole where icy shorelines shift in and out.

 

Text, Earth's climate is a complex system with many interconnected parts.

 

When one component of the system changes, it starts a chain reaction that affects everything else.

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A satellite image shows an expanse of green land beside a large block of ice.

 

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Text, Bear Glacier; Kenai Peninsula, Alaska.

 

As a glacier moves, it scours the surface carrying and later depositing any rocks and sediment it has gathered.

 

This jumble of rock and dirt is called a moraine.

 

Vertical stripes run down the length of ice. Lateral moraine is labeled between ice and land.

 

Text, Lateral moraines form when the sediment is pushed to the sides of the glacier.

 

Medial moraine is labeled in the middle of the ice block.

 

Text, The dark parallel racing stripes that run along the middle of the glacier are medial moraines that formed from lateral moraines as two glaciers merged.

 

A cove of bright blue water with floating chunks of ice at the bottom of the glacier.

 

Text, At the end of the glacier, melt water has pooled into a crystal-blue glacial lake.

 

Its color is the result of pulverized rock dust, or "glacial flour," that reflects sunlight, making the deep-blue water appear much brighter.

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Text, Myth vs. Reality

 

Myth. The surfaces of glaciers are smooth.

 

Reality. Although the area where snow accumulates on a glacier can be fairly smooth, the rest of the glacier is a jagged and jumbled array of melting ice pinnacles, rocks, and deep crevasses.

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Text, Helheim Glacier, Greenland

 

2001. Thin glaciers break more easily than thicker ones.

 

Between 2001 and 2003, Helheim Glacier thinned by 131 feet.

 

2003. Helheim's thinning allowed its edge to rapidly crumble into icebergs.

 

2005. Between 2001 and 2005, Helheim Glacier lost nearly 5 miles of ice from its tip.