WEATHERING, EROSION, AND DEPOSITION KNOW IT WHEN YOU SEE IT

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WEATHERING AND EROSION KNOW IT WHEN YOU SEE
IT
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By Mrs. Birtwell
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These images will help you to understand the
natural processes of WEATHERING, EROSION, and
DEPOSITION.
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WHAT ARE WE TALKING ABOUT?

• WEATHERING refers to the breaking down of rock by
  chemical or physical means.
• EROSION refers to the carrying away of these bits
  of rock by agents of erosion (the things that
  move the particles) such as wind, gravity,
  glaciers, and water.
• DEPOSITION refers to the bits of rock being laid
  down in a new place.

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CHEMICAL WEATHERING occurs when rock is broken
down by chemical reactions. For example, this
rock is being broken apart by chemicals produced
by these lichens.
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This tombstone has lost its lettering because of
ACID PRECIPITATION. This occurs when weak acids
in rainwater attack the minerals in a rock.
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Caves and formations like this are formed when
acid rain drips down and liquefies limestone
(calcite).
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MECHANICAL WEATHERING occurs when rock is broken
into smaller pieces by physical means.
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For example, these tree roots have wedged into a
piece of rock and cracked it apart. This is
called ROOT PRY.
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When water freezes, it expands. ICE WEDGING
probably cracked this boulder in half.
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This tombstone has also been mechanically
weathered, probably by ICE WEDGING.
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When one part of a rock wears away faster than
another part, it is called DIFFERENTIAL WEATHERING
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These cracks in granite are naturally formed, and
are known as JOINTS.
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EXFOLIATION occurs when layers of granite are
weathered and onion-thin layers peel off and away.
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This granite has been dissolved and smoothed by
chemical weathering.
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Lets talk about AGENTS OF EROSION.Once rock
particles break off, they might be carried away
by GRAVITYor WATERor WINDor GLACIERS.
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• GRAVITY is an important agent of erosion. Rocks
  can be eroded by simply falling down!

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Piles of rock that have weathered from the top of
a hill or mountain are called TALUS SLOPESwhen
they fall to the bottom.
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I am sliding down this Kansas talus slope, where
I found a lot of fossils already weathered out
of the rock.
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This is a SLUMP.
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This is called a LANDSLIDE.
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I stood on the side of this Canadian mountain and
examined this LANDSLIDE.
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This ALLUVIAL FAN is a fan-shaped
formation which occurs on land.
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WATER is also a significant AGENT OF EROSION
because it wears down bits of rock material by
EITHER chemical or mechanical means, carries them
to another location, and deposits them there.
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This is a DELTA, formed when a river has
deposited material at its mouth (at the juncture
of a river with the ocean).
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CANYONS are created when rivers carve down their
banks over thousands of years.
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This process also shapes the seashore. This is a
SEA ARCH, formed by the force of the ocean
against rock.
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This TOMBOLO was created when a sea arch finally
collapsed.
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WIND is another important AGENT OF EROSION. It
blows sand into DUNES.
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These cracks were formed when a lake dried up.
Wind will carry the bits away because the water
is no longer there to cover them.
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This is a MESA, created by WIND EROSION.
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BUTTES are sculpted when wind abrades soft rock
like limestone.
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GLACIERS huge formations of moving ice and snow
are powerful AGENTS OF EROSION.
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I photographed these glaciers in the Canadian
Rockies.
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When excavating the World Trade Center site in
New York City, construction workers found glacial
formations deep under the soil.
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• The World Trade Center site has been covered by
  soil and buildings for over 20,000 years.
• This means that until the site was cleared in
  2008, no human had ever seen them.
• The glacial formations included a hole made by
  rushing glacial meltwater over 100 feet deep.
• Unfortunately, all of it was filled in and
  covered over to build the skyscraper that will
  replace the Twin Towers!

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The End