Download Getting to Know: Erosion by Water

Getting to Know: Erosion by Water
The Grand Canyon is one of the most
breathtaking places in the world. As
you look over the rim of the canyon, it is
possible to see rock layers that are more
than one billion years old! The Colorado
River started eroding those rocks 5 to
6 million years ago. Today, the Grand
Canyon is vast and yet the Colorado River
continues to gradually erode its riverbed.
How do rivers cause erosion?
Flowing water acts as an agent of erosion
because it contains small pieces of rock
and sediment. These particles can wear
down and erode the rocks in a riverbed.
If a river contains a lot of fast-moving
water, it can rapidly erode Earth’s surface.
In addition to canyons, many landforms
result from the weathering and erosion
of Earth’s surface by water. Flowing water
also creates landforms by depositing
eroded material. For example, deltas
form at the end of rivers when material
transported in the water is deposited. A
delta is evidence that erosion by water has occurred. The Colorado River winds through the deep walls
of the Grand Canyon. Over millions of years, the
river has eroded the rock layers that make up this
magnificent landform.
Is there a difference between weathering and erosion?
Although weathering and erosion are related processes, they are different. Weathering is
the physical and chemical breakdown of rock. Erosion occurs when pieces of rock or soil are
moved away from their original location. Deposition occurs when the eroded material, also
known as sediment, comes to rest in a new location.
Misconception 1: Does all erosion happen on Earth’s surface?
Erosion can occur above and below Earth’s surface. Below Earth’s surface, water can seep
into the spaces between rocks. Over time, the water can weather and erode the rocks,
eventually causing caverns to form.
Concept: Erosion by Water
Getting to Know
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Where can I see evidence of erosion by water?
The evidence of erosion by water is everywhere. Have you ever looked at the ground after
a heavy rainstorm? One of the most damaging forms of erosion is soil erosion. Healthy soils
suitable for growing food can be easily eroded by water. If trees or other vegetation are
cut down, an area can be even more vulnerable to soil erosion. The soil, with no plants to
anchor it, erodes away.
Misconception 2: Is all erosion harmful to the environment?
Weathering and erosion are natural processes, and they can play an important role in
maintaining the health of ecosystems. In fact, they create soil by breaking down and
transporting rock material. Over time, this material becomes soil and without soil, plants
could not grow.
Do other water sources cause erosion?
Yes, oceans and many lakes are large enough
to have waves. The constant movement of
the waves can cause the erosion of rocks and soil near the shore. This is why you will see
sandy beaches on the shores of oceans and
lakes.
Ice also erodes rock material. A large glacier can cut through a mountain to form large
U-shaped valleys. As the glacier moves, it picks up large and small rocks, which get trapped in the ice. These rocks increase the rate at which a glacier erodes Earth’s surface.
Melting glaciers can also produce fast-moving
streams, which cause further erosion.
Glaciers erode and transport rock material.
This process is responsible for many of Earth’s
landforms.
In the lesson, you will learn more about
the ways that water can change the shape
of landforms over time. As you complete the activities, think about the human activities that alter the process of erosion by water. Perhaps you will find something you can do to minimize damage caused by erosion in your neighborhood. Concept: Erosion by Water
Getting to Know
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© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.