True or False: The Earth

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True or False The Earths surface has stayed the
same for thousands of years
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True or False The Earths surface has stayed the
same for thousands of years
False
The Earths surface is always changing!
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Weathering and Erosion
Wind Water Ice Gravity
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Weathering

• The breakdown of the materials of Earths crust
  into smaller pieces.

Weathering causes soil formation
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What is Mechanical Weathering?

• Breakdown of rock into smaller pieces without any
  change in the chemical composition of its
  minerals
• Sometimes called physical weathering
• Rock is torn apart by physical force, rather than
  by chemical breakdown
• Smaller pieces do not move to a new location
  until erosion carries them away

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Water causes weathering
What evidence of weathering do you see in this
picture?
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Wind causes weathering
Why wasnt this mass of land weathered away?
What evidence of weathering do you see in this
picture?
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Mechanical - Biotic

• Biotic means life
• Weathering caused by living organisms
• Plant roots act as a wedge and widen cracks
• Other causes of biotic weathering are digging
  animals, microscopic plants and animals, algae
  and fungi.

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Ice causes weathering
Describe how ice causes weathering?
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Mechanical - Ice Wedging

• Ice Wedging
• Water fills joints of rocks and freezes
• Water expands 10 when it freezes, pushes rock
  apart
• Repeated freeze and thaw cycles over the years
  causes rock to break along joint

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Erosion

• The process by which water, ice, wind or gravity
  moves fragments of rock and soil.

What evidence of erosion do you see in this
picture?
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What is Chemical Weathering?

• Breakdown of rock into smaller pieces because of
  change in the chemical composition of its
  minerals
• Chemical reactions break down the bonds holding
  the rocks together, causing them to fall apart
• Chemical weathering occurs in all types of rock
• Rock reacts with water, gases and solutions

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Chemical - Oxidation

• Oxidation - oxygen combines with other elements
  in rocks to form new types of rock
• New substances are usually much softer than
  original, easier for other forces to break rock
  apart
• Causes a rusting of the rock, often causes a
  color change in the rock

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Chemical - Carbonation

• Carbonation Carbon dioxide (CO2) is dissolved
  in water making carbonic acid
• Weak acid is formed when CO2 in the air mixes
  with rain. This is the same acid found in soft
  drinks. 
• Acid is too weak to harm plants and animals but
  slowly causes feldspars and limestone to
  decompose

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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?
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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.
• The intensity of wind erosion is determined by
• Sum (amount)
• Speed
• Slope
• Surface

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Wind Erosion
Creates sand dunes
Greatest impact in deserts
Removes fertile topsoil
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Water Causes Erosion

• runoff, rivers and, streams

Creates MOST of the changes in the Earth's
landscape!
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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.

Rivers and streams are a constant flow of
runoff- they constantly weather and erode!
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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
Ss?
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Ice Causes Erosion
Glaciers wear down the landscape by picking up
and carrying debris that moves across the land
along with the ice.
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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!
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Ice Causes Erosion

• How much erosion takes place is determined by
  the
• Sum (Glaciers are massive!)
• Slope
• Speed
• Surface

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Gravity causes erosion

• Creep, Slump, Landslides, Mudslides, and
  Avalanches.

Slower
Faster
These are examples of mass movement (or called
mass wasting)
landslide clip.mpeg
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Gravity causes Erosion

• How much erosion takes place is determined by
  the
• Sum
• Slope
• Speed
• Surface

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Plants CAN CAUSE weathering
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Plants CAN PREVENT erosion
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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

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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, soil-rich land is known as a
  Delta

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Canyons
This simple animation provides you with a
visualization of how the Colorado River has
"downcut" into the rock layers of the Grand
Canyon. How long it took to carve the Grand
Canyon is debated bygeologists. Some estimates
are between 6 and 8million years, which is very
recent by comparison.
Canyons are large valleys created by a river or
stream.
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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.
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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.
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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.