Transcript Weathering and Erosion

True or False: The Earth’s surface has
stayed the same for thousands of years
True or False: The Earth’s surface has
stayed the same for thousands of years
The Earth’s surface is always
changing!
Weathering
The breakdown of the Earth’s crust into smaller pieces.
Water causes weathering
What evidence of
weathering do you see
in this picture?
Wind causes weathering
Why wasn’t this mass
of land weathered
away?
What evidence of
weathering do you see
in this picture?
Ice causes weathering
Describe how ice
causes weathering?
Erosion
The process by which water, ice, wind or gravity moves
fragments of rock and soil.
What evidence of
erosion do you see in
these pictures?
Erosion is Movement of Sediment!
• This process, known as
Erosion, is gradually
wearing down the surface
of the earth.
• Erosion is the process by
which weathered rock and
soil (sediment) are
moved from one place to
another.
• Erosion carves the Earth's
surface creating canyons,
gorges, and even beaches.
What do you think has caused
this rock to look this way?
Wind Erosion
As the wind blows it picks
up small particles of
sand/sediment and blasts
large rocks with the
abrasive particles, cutting
and shaping the rock.
Wind Erosion
Water Causes Erosion
• runoff, rivers and, streams
Water causes Erosion
When rain falls to the Earth it
can evaporate, sink into the
ground, or flow over the land
as Runoff.
When it flows over land,
erosion occurs.
Runoff picks up pieces of rock
and "runs" downhill cutting
tiny grooves into the land.
Water causes Erosion
How much erosion takes
place is determined by
the amount of slope on
the surface and the
speed of the water
moving over the
surface, and the
amount of water
moving over the
surface.
Ice Causes Erosion
Glaciers can wear down the
landscape by picking up and
carrying debris as the glacier
moves across the land.
Ice Causes Erosion
Glaciers can pick up and carry sediment that ranges in size
from sand grains to boulders bigger than houses.
Moving like a conveyor belt and a bulldozer, a single
glacier can move millions of tons of material!
Ice Causes Erosion
How much erosion
takes place is
determined by the
size of the glacier,
the speed the glacier
is moving, and the
slope/surface of the
land it is moving on.
Size, speed, slope, and
surface….where
have you heard
those words before?
Gravity causes erosion
Creep, Slump, Landslides, Mudslides, and Avalanches.
Slower
Faster
These are examples of mass movement
landslide clip.mpeg
(or called mass wasting)
Gravity causes Erosion
How much erosion takes
place is determined by
the:
**Slope
**Speed
**Surface
Plants CAN CAUSE weathering
Plants CAN PREVENT Erosion
Deposition
Rock particles that are picked up and transported during
erosion will ultimately be deposited somewhere else
Deposition is the process by which sediments (small particles
of rock) are laid down in new locations.
• Together, Erosion and Deposition build new landforms.
• Deltas
• Canyons
• Meanders
• Floodplains
Delta
Where rivers meet the
ocean is called the
mouth of the river. Soil
and dirt carried by these
rivers is deposited at the
mouth, and new land is
formed. The new, soilrich land is known as a
Delta
Canyons
This simple animation provides
you with a visualization of how the
Colorado River has "downcut"
into the rock layers of the Grand
Canyon.
Canyons are large
valleys created by a
river or stream.
How long it took to carve the
Grand Canyon is debated by
geologists.
Some estimates are between 6
and 8
million years, which is very recent
by comparison.
Meanders
Meandering streams wander side to side as they
constantly seek out the lowest elevation.
This constant motion creates a series of S-shaped
“loops”.
Meanders
Stream Velocity varies from one side to the other side
of the “S”, resulting in erosion in some places and
deposition of sediments in others.
Floodplains
• Floodplains form along the
banks of mid-order streams
and larger rivers.
• These are low-lying areas
along the sides of a river
channel that have regular
times of heavy waterflow to
cause the river to spill over
and flood the land.
Now its your turn…
Today you are going to become earth scientists studying a
model of a world-famous landform: The Grand Canyon.
The canyon is almost 2 km deep in places, and geologists are very
curious about how it formed. Because the Grand Canyon can't be
brought into the classroom, a model of it can be created using a
stream table.
You will notice stream table at the edge of
several tables with a bucket on the floor to
catch water that flows out of the stream
table. On each stream table you will notice a
ruler with a cup placed on top. This cup
represents your water source such as the
Colorado River in the bottom of the Grand
Canyon. The earth material represents a
small section of the earth's surface, and the
1 liter of water that they will run through
the system represents thousands of years of
water flowing over the earth.
Please remember that you will
pour only 1 cup of water through
your stream table system.
Do not touch the tray or shake the
desks once the water starts
flowing.
Before your start, sketch a before
picture in your science journal.
We want to be able to see your
results.
You should be able to
different landforms.
Landforms are shapes of
the earth's surface. Some
landforms to look for
during your stream table
investigation are valleys,
flood plains, meanders,
deltas, and the mouth of
the stream.
Make sure that you
document them if you do
see them!
Remember, the purpose of this
investigation is so that you can see for
yourselves in a small way how water
runs over the earth and wears the earth
away. This process is called erosion.
Some materials, like loose sand and soil,
erode very quickly, but other materials,
like granite and sandstone, erode more
slowly. The cutting of the canyon in the
stream table model is an example of the
process of erosion.