Chapter 3: Erosion and Deposition
Lesson 1: Mass Movement
Erosion and Deposition
Erosion: the process by which natural forces
move weathered rock and soil from one
place to another.
 Sediment: pieces of rock, soil, or remains of
plants and animals.
 Deposition: when the agents of erosion
deposit, or lay down, sediment.

Erosion and Deposition

Weathering, erosion, and deposition work
together to wear down and build up Earth’s
surface.
What is Mass Movement?

Mass movement is caused by gravity, and
it causes sediment to move downhill (quickly
or slowly).
 Landslides
 Mudflows
 Slumps
 Creep
Types of Mass Movement
Mudflow: the rapid downhill movement of a
mixture of water, rock, and soil.
 Usually occur after heavy rainfalls in
normally dry areas.

Types of Mass Movement
Landslides: when rock and soil slide quickly
down a steep slope.
 Occurs most on unstable slopes (example:
roads along highways).

Types of Mass Movement
Slump: a mass of rock and soil suddenly
slips down a slope as one large mass.
 Occurs when water soaks the bottom of soil
that is rich in clay.

Types of Mass Movement
Creep: very slow downhill movement of rock
and soil.
 It is hard to visibly see creep happening, but
you can see proof in tilted poles and trees in
the ground.

Chapter 3: Erosion and Deposition
Lesson 2: Water Erosion
Water and Erosion
Moving water, called runoff, is the major
agent of erosion that has shaped Earth’s
surface.
 The amount of runoff depends on:

 Amount of rain
 Type of vegetation
 Type of soil
 Topography (shape of the land)
 Use of land
Water and Erosion
As gravity moves sediment downhill,
changes occur on Earth’s surface.
 Rill: tiny grooves in the soil
 Gully: large groove (channel) that only hold
water during rainstorms and usually dry up.

Water and Erosion
Water and Erosion

Stream: channel along which water
continuously flows downhill; rarely dries up.
 Large stream = river

Tributary: a stream of river that flows into a
larger river.
Water and Erosion

Rivers usually start as straight, narrow
courses that are fast-flowing. They can
create:
 Waterfalls
 Flood plains
 Meanders
 Oxbow lake
Waterfalls
Waterfalls occur when a
river meets a block of
hard rock.
 The river flows over this
part, but then erodes the
softer rock downstream.
 This eventually causes
the waterfall.

Flood plain
A flood plain is a flat, wide area of land along
a river.
 When the river floods, it covers this area and
deposits sediment here.
 They have very fertile soil.

Meanders
A meander is a loop-like bend in the course
of a river.
 as a river flows, it erodes the outer banks of
the river and deposits sediment on the inner
banks.

Oxbow Lake

An oxbow lake is a meander that has been
cut off from the river.
Water Deposition
When moving water slows down, it drops
(deposits) some of the sediment.
 Delta: sediment deposited where a river
flows into an ocean or lake.
 Alluvial fan: wide, sloping deposit of
sediment formed where a stream leaves a
mountain range.

Water Deposition
Chapter 3: Erosion and Deposition
Lesson 3: Glacial Erosion
Glaciers

Glacier: any large mass of ice that moves
slowly over land.

can form only in an area where more snow
falls than melts.
Continental Glaciers

Continental glacier: a glacier that covers much
of a continent or large island.

Currently covers about 10% of Earth’s surface,
and can flow in all directions as they move.

During ice ages, these cover a much greater
area of land.
 The most recent ice age caused the glacier to retreat
about 10,000 years ago.
Continental Glaciers
Valley Glaciers

Valley glacier: a long, narrow glacier that
forms when snow and ice build up high in a
mountain valley.

Usually move downward on the mountains
into valleys; generally moves slowly.

Temperatures rarely rise above freezing, and
the snow continues to build up.
Valley Glaciers
Glacial Erosion
Plucking: glaciers pick up rocks as they flow
over the land, and it moves the sediments
(sometimes as large as boulders) across the
land.
 Abrasion occurs between the rocks and the
land, gouging and scratching the bedrock.

Glacial Erosion
Glacial Deposition
Till: a mixture of sediments that a glacier
deposits directly on the surface.
 The till deposited at the edge of a glacier
forms a ridge, called a moraine.
 Kettle: small depression that forms when ice
is left in a glacial till. When the ice melts, it
leaves a “hole” which can then form with
water as a pond or lake.

Glacial Deposition
Other Terms
Fiord: when the sea rises, a valley fills with
water.
 Horn: sharp mountain peak
 Cirque: bowl-shaped hollow eroded by
glacier
 Arete: sharp ridge separating two cirques.
 Glacial lake: large lakes left by glaciers
 drumlin: long mound of till that is smoothed
by the glacier’s flow.

Other Terms
Chapter 3: Erosion and Deposition
Lesson 4: Wave Erosion
Wave Erosion
By impact: large waves hit rocks and break
them apart.
 By abrasion: waves carrying particles hit the
land and cause the rocks to break apart.

Wave Erosion
Headland: part of the shore that sticks out in
the ocean; harder rock that resists erosion.
 Sea cave: formed when a hollow area is
formed in a cliff on the shore.
 Wave cut cliff: when the rock below the cliff
erodes and collapses.

Wave Erosion
Wave Erosion
Sea arch: forms when waves erode a layer
of softer rock that underlies a layer of harder
rock.
 Sea stack: when an arch collapses, these
pillars of rock remain.

Wave Deposition
Beach: area of wave-washed sediment
along a coast.
 Longshore drift: waves usually hit the shore
at an angle and travel parallel to the shore;
sediments are deposited in this pattern.

Wave Deposition
Sandbar: long ridges of sand parallel to the
shore.
 Barrier beach: forms when storm waves pile
up sand above sea level, forming an island
parallel to the coast (easily damaged by
waves).
 Spit: beach that projects into the water;
results from something interrupting
longshore drift or a sharp turn in the coast.

Wave Deposition
Chapter 3: Erosion and Deposition
Lesson 5: Wind Erosion
Deflation

Most common way for wind to cause erosion
is deflation: when wind removes surface
materials and transports them.

Stronger winds can carry heavier sediments.

Desert pavement: wind blows all of the
sediments away, leaving only rocky material
behind.
Deflation
Wind Deposition

Sand dunes: deposit of wind blown sand;
shape depends on direction of the wind,
amount of sand, and presence of plants.
 They can be small or large
 They can move over time
 Plant roots help the dune from moving

Sleeping Bear Dunes
Wind Deposition

Loess Deposits: when fine (silt and clay)
sediments are carried and dropped in far
away locations.
 Helpful in forming fertile soil for farming.