GlaciersGlaciersGlaciersGlaciers

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Rivers of Ice

Glacier FactsFound on every continent- even Africa!Cover 10% of the earth’s land areaContain 75% of the freshwater on earthTwo types:

Alpine (valley glaciers) are found in the mountains

Continental glaciers (ice sheets) are found at the north and south poles

How does a glacier form?Form when more snow falls than melts in one year

Snow compacts into iceIce begins to flow downhill under its own weight

How do glaciers work?In winter, ice accumulates at the top of the glacier, pushing the glacier downhill

In summer, ice melts at the bottom of the glacier

If the amount that melts in the summer is more than the amount that accumulates in the winter, the glacier retreats

Holgate Glacier, Alaska, July 1909Holgate Glacier, August 2004

Why are retreating Glaciers bad?

• Glaciers store water and release it later in the year• Snow accumulates in the winter• Melting snow feeds rivers in the summer• Less snow in the winter means less water in the summer for cities and farming

Qori Kalis Glacier, Peru, July 1978Qori Kalis Glacier, July 2004

The size of glaciers relate to sea levelIn earth’s past sea level was lower because there were more glaciers

As glaciers melt now, sea level will riseCould flood coastal cities

Why do geologists care about glaciers?Glaciers are a force of nature on earthGlaciers have shaped the landscape that we see now!

Glacial ErosionAs a glacier moves down the side of the mountain, it scrapes off pieces of the surrounding rock

Over time, a large amount of material can be removed by the glacier

Glacial Features: U-Shaped ValleysWhen a river erodes a valley, the valley

becomes V-shaped Glaciers are wider than rivers, so they

change the shape of the valleyValley becomes U-shaped

Glacial Features: Sharp Ridges (Aretes)Two glaciers on two sides of a mountainWhen glaciers melt, a sharp ridge remains

Glacial Features: Pyramid Peak (Horn)A peak where several sharp ridges meetAt least 3 very steep (nearly vertical) sides Form where several glaciers meet

Glacial Features: MorainesA pile of rocks that is pushed along as a glacier moves

Can vary in size