Earth Movers - Glaciers
By Patti Hutchison
Have you ever made a snowball with your hands? You pick
up some snow and press it together in you hands. It quickly
freezes into ice. If you have done this, you have made a "mini"
glacier.
1
Real glaciers, of course, are much, much larger. But they
are formed in the same way. Glaciers are mostly found in
areas of high latitude or high elevation. These places have cold
temperatures all year. Snow falls and never completely melts. The weight of the snow
on top causes pressure on the layers of snow beneath. The snow underneath
recrystallizes into ice.
2
Glaciers cover about ten percent of the earth today. Even at the peak of the last ice
age, only about thirty percent of the earth was covered. But glaciers made their mark in
much of the northern hemisphere.
3
There are two types of glaciers - continental glaciers and valley glaciers. Continental
glaciers cover huge areas. As you can guess, they can be as big as continents. They
are thickest in the middle. The pressure in the middle causes the glacier to spread out
and cover large areas. Today these glaciers cover Antarctica and parts of Greenland
and Canada.
4
A valley glacier is much smaller than a continental glacier. They form in areas with
high mountains. They form when a mass of ice becomes too thick. The weight causes it
to start to move slowly down the valley. Deep cracks form in the ice.
5
Glaciers are probably the most powerful force of erosion. Their mass allows them to
move huge amounts of rock and land with them. As they melt and move back, the
landscape is changed.
6
The bedrock beneath a moving glacier is carved out. It is kind of like scooping ice
cream out of the carton. U-shaped grooves are formed as the glacier moves down the
slope.
7
If there are glaciers on three sides of a mountain, they carve out a pyramid shape.
This is called a horn.
8
Glaciers also cause lakes to form. The Great Lakes were formed by glaciers. Large
blocks of ice break off the glacier. They are covered with sediment. When the ice melts,
a deep depression is formed in the bedrock. They fill with water and form a lake.
9
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The last ice age ended over 10,000 years ago. The massive glaciers drew back.
They left scars in the bedrock. They have become some of the earth's most
interesting geographic features.
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Earth Movers - Water
By Patti Hutchison
You know that most mass movements are caused by
gravity. Water is another powerful force that can cause the
movement of large masses of earth. Movement of rocks and
soil can be caused by too much water or too little.
1
If there is too little water on a slope, particles have
trouble holding together. It's sort of like trying to make a
snowball out of dry, powdery snow. It just won't keep its shape. Wet snow stays
together easily. The same is true of soil. Water helps hold the grains together. If the
grains are dry they can be moved easily by wind or gravity.
2
Sometimes there is too much water on a slope. The particles become loose.
Water adds to the weight of the earth materials. It also reduces the friction of the
surfaces. It is easier for gravity to pull the soil and rocks downhill.
3
Mudslides are mixtures of mud and water. They move very quickly. They are
common in areas with steep slopes that get short, severe rainstorms. California is
an area that frequently has mudslides.
4
Places that have mudslides receive little rainfall most of the time. The slopes
have few plants and trees. Heavy rainfall occurs in short bursts. The water carries
the soil quickly downhill.
5
Volcanic eruptions can also cause mudslides. The eruption of Mount Saint
Helens in 1980 caused destructive mudslides. The heat from the lava quickly
melted the snow on the mountain. The rushing water moved soil and other particles
down the slope. This caused major damage to homes at the bottom of the
mountain.
6
Mudslides are an example of how water can cause quick erosion. Water can
also erode materials slowly. This process is called abrasion. Rivers and streams
carry particles of sand and rock along with them. These materials rub up against
the rock and soil on the bank. Slowly, over a long time, the bank wears away. The
stream becomes wider or deeper.
7
The Grand Canyon is an example of erosion by water. It was formed over
thousands of years as the Colorado River abraded the rock it flowed through. This
process is still going on there today.
8
9
Water erosion can also be beneficial. Particles that are carried along are finally
deposited in a larger body of water. Over time they build up. A delta is formed.
Deltas are areas of very fertile soil.
Moving water is a powerful force. It can change the landscape quickly or
slowly. It can be helpful or harmful.
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Copyright © 2013 edHelper
Name _____________________________
Date ___________________
Earth Movers - Water
1. Mass movements can be caused by
too little water on a surface.
False
True
3. Why do most mudslides happen in
areas where there is little rainfall?
Because the soil is very wet
Because the particles are
packed tightly together
Because there are few plants to
hold the soil in place
5. Water can erode earth materials
slowly through a process called
______.
Deflation
Avalanche
Abrasion
2. Explain two ways too much water
can help gravity move materials.
4. How can a volcano cause a
mudslide?
6. What is formed when particles
carried by a river are deposited in a
larger body of water?
A delta
A mudslide
A canyon
Earth Movers - Glaciers
1. Where are glaciers mostly found?
2. What percent of the earth is covered
with glaciers today?
20 percent
50 percent
10 percent
3. Name the two kinds of glaciers.
4. Glaciers on three sides of a mountain
form a pyramid shape called a ______.
Valley
Horn
Lake
5. The Great Lakes were formed by
glaciers.
False
True
6. How long ago did the last ice age end?
1000 years
1.5 million years
10,000 years