Wearing Down Earth’s Surface
Chapter 6 Lesson 2
C14 – C19
Identify destructive forces as processes that wear down
Earth’s land features.
Identify weathering as a destructive force.
Recognize that weathering can be either mechanical or
Define erosion as the carrying away of weathered rock by
water, wind, and glaciers.
Destructive forces, such as weathering and erosion,
wear down Earth’s surface features.
Erosion – (noun), destructive force in which pieces
of rock are moved by water, wind, or moving ice.
Sediment – (noun), small pieces of rock
Weathering – (noun), destructive force that breaks
down rocks into smaller pieces
A destructive force that breaks down rocks.
The breaking of larger rock into smaller rock called
Ice – water goes into cracks of rocks, freezes, and
breaks rock apart.
Moving air & Water – causes weakening of rock
and it will crumble
Living things – plant roots and burrowing animals
Rocks change into other materials
Water is the main factor causing chemical
Water dissolves minerals that make up certain rock
Water dissolves certain chemicals from the air & soil to
form a weak acid – which dissolves minerals
Underground hollow areas
created by weathering
Weak acids seep into the
Acid dissolves minerals in rock
Over time, holes produced in
At first full of water, but
eventually water drains
Many caves are made
The minerals in limestone
is easily dissolved by
Describe three ways that mechanical
weathering may occur?
Water in the cracks of rocks, freezes, and busts
rock into smaller pieces
Wind or rushing water hitting rocks causes them to
weaken and crumble.
Plant roots breaks apart rock.
Why do many caverns form in
The minerals in limestone are easily dissolved by
The carrying away of sediments by moving water,
wind, or moving ice
Common agent of erosion: Water moving down a
River Valley Formation
Begins as a shallow
stream at higher
Stream grows and
carries sediment away
In time, the river cuts
a V-shaped valley
Glaciers formed the rolling
plains and the Great Lakes.
Glaciers move down stream
toward the sea.
Move large amounts of rock &
They form hallows in the land
they erode. When they melt
they form lakes.
Ocean waves & Currents
Crashing waves break down rock along coastlines.
Sediments are dragged back and forth, slowly turning
Wind & Waves erode the land.
Sea caves may join to form a sea arch.
Erosion may continue until arch falls creating a sea
Weathering vs. Erosion
Process that breaks down The carrying away of
rock into smaller pieces sediments by moving
called sediment water, wind, or moving ice
Slow and Fast Changes
Chemical weathering = takes thousands of years
But, after a cave is formed, the weight my be to
great causing a sudden collapse which forms a
Form very suddenly
Land above weathered rock
sinks into a hole.
Occur suddenly due to
Large movements of land
that tumble down a steep
Mudslides, rock falls, &
Causes of landslides
Gravity is the main cause
Erosion from rivers, rain, glaciers, or ocean water
These steepen the slope and loosen sediment
A disturbance, such as an earthquake, can shake
the rocks loose.
Volcanoes can cause landslides also.
How are a sinkhole and a landslide
alike? How are they different?
Occur quickly Sinkhole is formed when
Result of weathering & rock above a cave falls
erosion into the cave
Gravity pulls sediment In a landslide, rocks and
downward soil tumble down a hill.
What are the four forces that can
combine to cause a landslide?
Erosion loosens sediments making a steep slope
Rain causes sediments to become heavy with water
Earthquakes shake the sediments loose
Gravity carries the sediments downhill
Turn to page C19 to answer the Review
Rocks break down during a destructive
process called what?
This forms when agents of mechanical
weathering break rocks into smaller
Wind, water, and moving ice move
sediments during the process of
The rocky outer layer of Earth’s surface
is called the ________.
A ______ map shows the shape of
surface features and their elevations.
A flat landform found at a high elevation
is called a ______.
Earth’s crust consists mostly of
B. Pressurized metals
D. Solid Rock
Earth’s crust consists mostly of
D. Solid Rock
List three causes of mechanical
Plant & animal activity
Describe how chemical weathering can
take place below Earth’s surface.
Water seeps into deep cracks and dissolves minerals
Acid rain seeps into cracks in rock and dissolves
below the surface.
Wind, running water, and glaciers lead to erosion.
Which one moves sediments most quickly?
Which moves sediments most slowly? Which is
capable of moving the heaviest sediments?
Fast-flowing water & high speed winds can carry
small sediments quickly.
Glaciers move most slowly, but are capable of
carrying large amounts of sediment with them.