Transcript Erosion Power Point

Erosion
is the process by which
natural forces move
weathered rock and soil
from one place to another.
Erosion can occur
quickly or slowly.
Erosion
occurs because
of the actions of
gravity, ice,
wind, and water.
When gravity alone
causes rock or
sediment to move
down a slope, the
erosion is called
mass movement.
4 Types of Mass Movement
• Creep – Sediments move downhill very
slowly.
• Slump – Rock or sediment moves
suddenly downhill in one large mass.
• Rockslides & Landslides – Layers of
rock or land break loose and slide quickly
downhill.
• Mudflows – A mass of wet sediment
flows rapidly downhill.
When glaciers get thick
enough, gravity causes
them to flow downhill.
As they move, they erode
materials from some
areas and deposit
sediment in other areas.
2 Types of Glaciers
• Continental Glaciers spread out in
all directions. They cover much of a
continent or large island.
(ex: Antarctica and Greenland)
• Valley Glaciers move down valleys
that have already been cut by rivers.
They are much smaller but can still be
tens of kilometers long.
Glaciers cause erosion
by two processes:
• As a glacier flows over land, it picks up
rocks. This process is called
plucking. When the glacier moves, it
carries the rocks with it.
• Many rocks remain on the bottom of
the glacier and get dragged across the
land, making scratches and gouges.
This process is called abrasion.
New landforms can be
developed when glaciers
melt and deposit the
sediment they have been
carrying.
Wind by itself is the
weakest agent of erosion.
It can still be a powerful force
in shaping the land in areas
where there are few plants to
hold the soil in place.
Wind blows small, loose
sediment from Earth’s
surface, but often leaves
behind particles that are
too heavy to move. This
process is called
deflation.
When sediments are
blown by strong winds,
abrasion
can make pits in rocks
and produce smooth,
polished surfaces.
When wind blows around
an obstacle, it slows
down. This causes sand
that is carried by the wind
to be deposited,
sometimes forming
sand dunes.
Water is a major
agent of erosion.
Streams are the
most important
agent of erosion on
Earth!
Water that flows over Earth’s
surface is called
runoff.
This water carries loose
sediment with it causing
erosion. The more speed water
has, the more material it can
carry with it.
As runoff travels, it forms tiny
grooves in the soil called
rills.
As many rills flow into one another,
they grow larger, forming gullies.
As many gullies join together, they
form streams,
which can eventually grow larger
and form rivers.
Anytime moving water
slows down, such as when
rivers enter oceans or lakes,
sediment is deposited. This
can create landforms such
as sand bars and deltas.
This is known as
deposition.
When rain falls or snow
melts, not all of the water
evaporates or becomes
runoff. Some water soaks
into the ground.
This groundwater can cause
erosion, forming caves and
making stalactites and
stalagmites.
Acting like drills or buzz saws,
waves erode the solid rock of the
coast into cliffs and caves.
Large waves can hit rocks along
the shore with great force,
eventually causing pieces of rock
to break off.
Waves also cause the sediment
they carry to wear away rock
through abrasion.
Waves also deposit sediment
they are carrying, forming
features such as beaches.