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Changing Earth’s
Surface
8.1 Weathering
Changing Earth's Surface
• Weathering
– The process that breaks down and changes rocks
that are exposed at Earth’s surface
• Erosion
– Moving weathered material from one place to
another
• Deposition
– Sediment is laid down at a new location
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2.1 Landforms
Shaping the Earth with Water
• Most erosion is done
by water.
• Rivers, ocean currents,
and ice (p. 334, 342)
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Rivers
Rivers
• Streams and rivers are active systems
that erode land, transport sediment,
and deposit sediment.
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8.2 Erosion and Deposition
Deposition
• Sediment and rock that are eroded and
carried by river systems are transported
and eventually deposited at a new location.
– Oxbow lakes
– Delta
– Alluvial fans
(Page 345)
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Flooding
8.2 Erosion and Deposition
Flood
• When the water level in a river rises above
the usual height and overflows its banks
• Floodplain: a wide, flat valley located
along the sides of rivers and streams
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8.2 Erosion and Deposition
Levees
• Protect area from flooding
– Natural levees: long, low ridges formed
by sediment carried by floodwaters and
deposited along the floodplain
– Artificial levees: human–made structures
built to help control floodwaters (p. 348)
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Beaches
8.2 Erosion and Deposition
Beaches
• Landform consisting of loose sand and gravel
• Dynamic, actively changing systems
• Sand supplied by the continuous flow of
rivers to oceans
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8.2 Erosion and Deposition
Erosion Features
• Cliffs: formed by the cutting action of waves
• Eroded cliffs move back from the shoreline
and leave behind a flat area called a wavecut platform
• Sea caves, sea stacks, and sea arches
can form when waves erode the softer
portions of rocks.
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8.2 Erosion and Deposition
Longshore Current
• Movement of
the water that
moves large
amounts of
sediment along
coasts
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8.2 Erosion and Deposition
Erosion Prevention
• Shoreline armoring: retaining walls, harbor
channels, and groins
• Changes natural shoreline processes but is
necessary to prevent collapse of cliffs or the
complete destruction of a beach. (p. 349)
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Glaciers
8.2 Erosion and Deposition
Glaciers
• Large masses of ice and snow
• Form in areas where amount of annual
snowfall is greater than the meltoff
• Formation takes hundreds to thousands
of years
• Movement is about 2.5 cm/day
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8.2 Erosion and Deposition
Glaciers (cont.)
• Valley glaciers (alpine glaciers): form in
existing stream valleys high in the mountains
• Continental glaciers (ice sheets): cover entire
land areas, only located in Antarctica and
Greenland
• Video
(Page 350)
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Glaciers
shape the land
8.2 Erosion and Deposition
Glaciers and Erosion
• Glaciers erode surfaces
as they pass over them.
U-shaped valleys.
• Trapped rocks and boulders at
the bottom of the ice create
grooves and scratches as the
glacier moves.
• Grooves and scratches show
the direction the glacier was
moving. (striations)
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8.2 Erosion and Deposition
Deposition and Glaciers
• Till: sediment deposited by glacier. Often
builds up along the sides and fronts of
glaciers into long, high ridges called
moraines
• Outwash: sediment
deposited by glacial
river; consists mostly
of sand and gravel
(p.351)
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Mass
Wasting
8.2 Erosion and Deposition
Mass Wasting
• Form of erosion caused by gravity
• Downhill movement of rocks and/or soil in
one large mass
• Usually occurs when the ground is
saturated with rainwater but can be
triggered by vibrations from earthquakes,
heavy machinery, and blasting
• Steeper the slope of hillside, the more likely
mass wasting will occur
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Mass Wasting (cont.)
8.2 Erosion and Deposition
• Landslides: rapid, gravity-caused events
that move soil, loose rock, and boulders
• Mudslides: mixtures of soaked soil and rock
• Rock falls: loosened rock falling from
steep cliffs
• Slumps: a block of rock and overlying soil slide
down as one large mass
• Creep: sediment moves slowly downhill
• (p.343)
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Climate & Erosion
8.2 Erosion and Deposition
Climate and Erosion
• Climate determines amount of water a
region receives
• Regions with large amounts of rain more
likely to experience mass wasting
• Presence of thick vegetation on slopes
tends to prevent landslides because the
plants’ root systems hold sediment in place
(p.344)
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