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!
Earth’s Changing Surface

Weathering, erosion, and deposition act together in a
cycle that wears down and builds up Earth’s surface
Weathering
– Breaks down
Deposition –
deposits / builds
Erosion
moves
-
Weathering
The breakdown of Earth’s crust into smaller
pieces.
Must occur before
erosion can happen
 No movement usually
occurs.
 Sediments- naturally
occurring material that
is broken down by
processes of
weathering;
small/tiny pieces of rock

Physical/Mechanical
Weathering
the process of breaking down Earth’s surface
into smaller pieces – similar to a physical
change
Physical Weathering -- The steep walls here
were carved out by moving water
Palo Duro Canyon in the High
Plains Eco-Region
1.Water
2.Ice
3.Wind
4.Gravity
5.Organisms
Causes of Physical
Weathering
Enchanted Rock in the Llano
Uplift Eco-region
Exfoliation-warming and cooling
of rocks over time causes rocks
to peel into sheets
Chemical Weathering
Chemical weathering occurs when chemical reactions
dissolve the minerals in rocks or changes them into
different minerals (rusting, acid breakdown, etc)
This cave was formed by
slightly acidic water
dissolving the limestone
Causes of Chemical
Weathering
Natural Bridge Caverns in Texas
1.Oxidation
2.Hydration
3.Carbonation
Let’s compare


Please draw a Venn diagram and compare
chemical and physical weathering.
How are they similar/different?
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 move sediments.
What evidence of
erosion do you see in
this picture?
Erosion is Movement of
Sediment!
• 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?
Erosion is Movement of
Sediment!
The intensity of erosion is determined
by the 4 S’s:
•
•
•
•
Sum (amount)
Speed
Slope
Surface
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
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
(called rills) into the land.
Water Causes Erosion
• runoff, rivers, and streams
Water causes Erosion
How much erosion
takes place is
determined by the:
• Sum (amount)
• Slope
• Speed
• Surface
Can you act increasing
and decreasing the
four S’s?
Ice Causes Erosion
Glaciers wear down the
landscape; by picking up and
carrying debris that moves
across the land along with
the ice.
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:
• **Sum (Glaciers are
massive!)
• Slope
• Speed
• Surface
Gravity causes Erosion
Gravity is the force that moves
rock and other materials
downhill.
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:
• Sum
• **Slope
• Speed
• **Surface
Bare Slopes vs. Vegetation Stabilized
Slopes
How do weathering, erosion and depostion impact
each side of the “hill”?
Bare Slopes vs. Vegetation
Stabilized Slopes
• Mudslide danger
• Loss of topsoil
• Clogged storm drains
• Flooding problems
• Expensive clean up
• Eroded or buried
house foundations
Bare Slopes vs. Vegetation
Stabilized Slopes
• Mudslide danger
• Loss of topsoil
• Clogged storm drains
• Flooding problems
• Expensive clean up
• Eroded or buried
house foundations
• Soil in place
• Less clean up
• Minimum erosion
• Protection
for house
foundations
Plants CAN CAUSE weathering
Plants CAN PREVENT erosion
Erosion
Galveston Texas before/after Hurricane Ike
Deposition
Deposition is the process by which sediments are
deposited in new locations.
• Together, Erosion and Deposition build new
landforms.
Delta
Soil and dirt carried by these rivers is deposited at the
mouth (where rivers meet the ocean), and new land
is formed. The new, soil-rich 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 - Extra Info
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 are an area
of land that is prone to
flooding.
• 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.
WED
Look at the picture of Galveston above, what do you
think will happen to this land if another hurricane
hits the Galveston coast? Explain each component
and how will the island be effected.