Download Chapter 10: Erosion and Deposition

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Objectives
 Explain how flowing water causes erosion and
deposition
 Describe how runoff, streams, and rivers change
Earth’s surface
 Identify features caused by groundwater erosion
and deposition
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Erosion – transportation of sediments
Agents of erosion include flowing water,
wind, waves, ice, or gravity.
Eroded materials drop somewhere. This is
called deposition.
Rate of erosion depends on velocity of
running water. Fast water  larger particles
and more particles transported
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Minerals that dissolve in water form salts.
Small particles such as clay and silt are carried
in a suspension, not dissolved in water.
Medium sized particles as such as sand,
moved by saltation. They jump at the bottom
of the stream.
Large particles like gravel and pebble move
by traction – dragged at the bottom of the
water.
Eventually the particles are deposited.
This can happen by runoff, streams, and rivers.
Erosion by runoff – when rain is not able to absorb into the
ground, it may pick up loose material on the surface and
move it somewhere else.
 Erosion by streams –
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 Mountain – steep slope carries a lot of sediment down V-shaped
channel. If softer rock erodes next to harder rock  waterfall
can form.
 Slow-Flowing rivers
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Gentle slopes erode the sides of the channel more than the bottom.
These large curves are called meanders.
Meanders erode from side to side, create a floodplain.
A meander may cut off from the rest of the river forming an oxbow
lake.
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The slope has much to do with the sediment
moving. Deposition occurs when the slope
becomes more gradual and movement slows
down.
 Alluvial Fan – deposits at the bottom of a
mountain stream, flat land.
 Delta – deposits where a stream or river empties
into still water. It forms a triangle shape.
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Flood waters will spread out sediment and
deposit it over the land.
Flood plain develops a thick layer of soil from
all the deposits.
 Good for growing plants/crops.
 Forms natural levees – raised strip of sediments
deposited close to the water’s edge.
Some water soaks into the ground into the soil, seeps
through the rocks, can erode/deposit materials.
 Water can dissolved rock and form caves. Water is
dissolved in minerals. When minerals come out of a
solution, they are deposited.
 Formations build up in caves –
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 Stalactites – pointed, icicle-like mineral from ceiling of
cave down
 Stalagmite – rounded mineral deposit from the bottom of
the cave up
 Sinkhole – when the erosion continues and the ceiling of
cave collapses.
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Objectives
 Explain how waves cause erosion on shorelines
 Describe features formed by wave deposition
 Identify ways to protect shorelines from wave
erosion
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Waves – the way energy travel through
matter.
Ocean waves form when wind blows over the
surface of the ocean.
Wind energy is transferred to to the sea
surface and is carried through by waves.
Factors that determine size of waves
 Speed of the wind
 Length of time the wind blows
 Distance the wind blows
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Wave Erosion – Runoffs, streams, and rivers
carry sediment to the oceans and act like
sandpaper. They erode the shore.
Landforms From Wave Erosion
 Sea Arches form when waves erode both sides of
a cliff.
 Sea Stacks – form when waves erode the top of a
sea arch, leaving behind pillars of arch.
 Wave-cut cliffs when rocks erode a rocky
shoreline
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Beaches- sediment in the form of sand
deposited in quiet areas along a shore. Shore
can include rock and shell in addition to sand.
Longshore drift – moves the sediment
straight down the beach with the direction of
the wave.
Spit – deposits from longshore drift, a ridge
of sand that extends away from the shore.
Sandbars and barrier islands can form from
wave deposits.
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Breakwaters – artificial barriers that protect
the shoreline from incoming waves.
Groins – A wall of rocks or concrete that juts
out into the ocean perpendicular to the
shore.
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Objectives
 Explain how wind causes erosion
 Describe sediment deposited by wind
 Identify ways to prevent wind erosion.
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Wind carries particles in the same way that
water carries them.
Tiny particles move through suspension, they
hang in the air for days. They go far distances.
Medium sized particles move by saltation. They
move in short hops and stay close to the ground.
Large sized particles move by traction. They
stay on the ground.
Abrasion is a form of wind erosion where rocks
are scoured and polished from wind itself or by
being dragged over surfaces.
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Like water, when wind slows down it drops the
sediments its carrying.
As wind slows down, it deposits the largest
particles first.
Sand dunes – deposits of sand found mainly in
deserts and beaches. Formed from an
obstruction slowing down wind, sand is then
deposited.
Loess – wind dropping fine particles of silt and
clay, forms vertical cliffs. It can become a thick,
rich soil.
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Covering soil with plants
 Plants and roots help the soil to stay in place
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Planting rows of trees around fields
Fences at beaches
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Objectives
 Describe how continental and valley glaciers form
 Explain how glaciers cause erosion
 Identify landforms deposited by glaciers
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Glaciers are masses of flowing ice
Two types of glaciers: continental and valley
Continental glacier is spread out over a huge
area. It may cover most of a continent or
large areas such as Greenland or Antarctica.
Valley glacier is long and narrow. It forms in
mountains and flow downhill through
mountain river valleys.
Glaciers form erosion in two main ways:
plucking and abrasion.
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Plucking – the process by which rocks and other
sediments are picked up by glaciers.
Abrasion – the process in which a glacier scrapes
underlying rocks.
Erosion by Valley Glaciers
 Carves out U-shapes valley with nearly vertical walls
 Cirque is a rounded hollow carved in the side of a
mountain by a glacier.
 Arete – a jagged ridge that remains when cirques
form on opposites sides of a mountain.
 Horn – a sharp peak that is left behind when glaciers
erode all sides of a mountain
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Glacial till – a mixture of particles and rocks of all
sizes
Moraine – sediment deposited by a glacier. A
ground moraine is a thick layer of sediment left
behind by a retreating glacier.
Drumlin – a long, low hill of sediment deposited
by a glacier.
Esker – a winding ridge of sand deposited by a
stream of meltwater.
Kettle Lake – occurs where a chunk of ice was
left behind in the sediments of a retreating
glacier.
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Objectives
 Identify causes and effect of landslide s and
mudslides
 Explain how slump and creep occur
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Mass movement – the type of erosion and
deposition by gravity.
Gravity can pull soil, mud, and rocks down cliffs
and hillsides.
Landslides – most destructive type of mass
movement. Happens when a large amount of
soil and rock suddenly falls down a slope
because of gravity. More likely if there has been
heavy rain or an earthquake. If a landslide falls
into a body of water  tsunami could form
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Mudslide – a sudden flow of mud down a
slope due to gravity.
 Occurs where soil is mostly clay.
 Forms usually with lots of rain  mud slippery
and slides
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Slump – a sudden mass movement of large
blocks of rock and soil down a slope.
Creep – slow movement of rock and soil
down a hillside. Happens so slowly you can’t
see it happening.