Section 7.2
Erosion and Deposition
Objectives
Describe the relationship of gravity to all
agents of erosion.
Contrast the features left from different
types of erosion.
Analyze the impact of living and nonliving
things on the processes of weathering
and erosion.
CH
7
Study Guide
Key Concepts
Section 7.2 Erosion and
Deposition
Erosion transports weathered
materials across Earth’s surface until they
are deposited.
 The processes of erosion and deposition have
shaped Earth’s landscape in many ways.
CH
7
Study Guide
Key Concepts
Section 7.2 Erosion and
Deposition
 Gravity is the driving force behind major
agents of erosion.
 Agents of erosion include running water,
waves, glaciers, wind, and living things.
Section 7.2
Erosion and Deposition
New Vocabulary
erosion
rill erosion
deposition
gully erosion
Section 7.2
Erosion and Deposition
Gravity’s Role
The removal of weathered rock and soil
from its original location is a process
called erosion.
Erosion can remove material through a
number of different agents, including
running water, glaciers, wind, ocean
currents, and waves.
Section 7.2
Erosion and Deposition
Gravity’s Role
After the rock and soil are transported,
sometimes thousands of kilometers
away from their source, they are
dropped in another location in a
process known as deposition.
Section 7.2
Erosion and Deposition
Gravity’s Role
Gravity is associated with many erosional
agents because the force of gravity tends
to pull all materials downslope.
Section 7.2
Erosion and Deposition
Erosion by Water
Stream erosion can reshape entire
landscapes. Water flowing down steep
slopes has additional erosive potential
resulting from gravity, causing it to cut
downward into the slopes, carving steep
valleys and carrying away rock and soil.
•
Dead Horse Point Overlook, with the Colorado River flowing 2,000 feet
below. 300 million years of erosion has carved the expansive canyons,
cliffs and walls below and surrounding Deadhorse Point.
River eroding volcanic
ash flow Alaska
Southwest, Valley of
Ten Thousand Smokes
•
Horseshoe Bend. The Colorado River makes a 180-degree turn at Horseshoe
Bend. Here the river has eroded the Navaho sandstone for eons, digging a
canyon 1100-feet deep
.
Section 7.2
Erosion and Deposition
Erosion by Water
Rill erosion develops when running
water cuts small channels into the
side of a slope.
When a channel becomes deep and
wide, rill erosion evolves into
gully erosion.
Section 7.2
Erosion and Deposition
Erosion by Water
Rivers and streams
Once a river enters the ocean, the current
slows down, which reduces the potential
of the stream to carry sediment. As a
result, rivers deposit large amounts of
sediment near the region where they
enter the ocean. Over time, deltas form.
Section 7.2
Erosion and Deposition
Erosion by Water
Wave action
The work of ocean currents, waves, and
tides carves out cliffs, arches, and other
features along the continents’ edges.
• The Mississippi River Delta, showing the
sediment plumes from the Mississippi and
Atchafalaya Riltaic Rivers.
Section 7.2
Erosion and Deposition
Erosion by Water
Wave action
The constant movement of water and the
availability of accumulated weathered
material result in a continuous erosional
process. Deposition of sand particles forms
features such as beaches and sandbars;
erosion removes sand from these features.
• Waves pounding at Venus Bay, South Africa
• Wave cut platform caused by erosion of cliffs
by the sea at Southerndown in South Wales
Section 7.2
Erosion and Deposition
Glacial Erosion
Because glaciers can move as dense,
enormous rivers of slowly flowing ice,
they have the capacity to carry huge
rocks and piles of debris over great
distances and grind the rocks beneath
them into flour-sized particles.
• V Shaped Valley from Glacial Erosion
• Tallus slope
Section 7.2
Erosion and Deposition
Glacial Erosion
The features left in the wake of glaciers
include steep U-shaped valleys and lakes.
• Iceberg Lake
Section 7.2
Erosion and Deposition
Glacial Erosion
The effects of glaciers on the landscape
also include deposition. For example,
soils in the northern parts of the United
States are formed from material that was
transported and deposited by glaciers.
• Rolling terrain as a result of glaciers
• As the glacier moves, the rocks on the
bottom move across the land.
• “plucked” land from a glacier
Section 7.2
Erosion and Deposition
Wind Erosion
Wind can be a major erosional agent,
especially in arid and coastal regions,
which tend to have little vegetation to
hold soil in place. Wind can easily pick
up and move fine, dry particles.
• Rock formation in Bolivia
• Moab Alcove
Section 7.2
Erosion and Deposition
Wind Erosion
The abrasive action of windblown particles
can damage both natural features and
human-made structures. Winds can also
easily move fine-grained sediments and
sand uphill.
• Mt. Rushmore
Section 7.2
Erosion and Deposition
Erosion by Living Things
As plants and animals carry out their life
processes, they often move Earth’s surface
materials from one place to another.
• Dirt bikes caused the erosion in this picture.