Transcript Review - carolynporter

Warm-Up
A tree root is growing into rocks on the
side of a hill. What do you think is
happening and how will it affect the
rocks?
Weathering
Earth’s Changing Surface
 Weathering,
erosion and deposition act
together in a cycle that wears down
and builds up Earth’s surface.
What is weathering?

The process where rocks are broken into
smaller rocks.
What is mechanical weathering?

Occurs when rocks are broken into smaller
pieces by physical processes.
…by plant activity

Roots grow in cracks
of rock
– As roots grow, so does
the crack
…by animal activity

Burrowing animals
(worms, rabbits, etc.)
create holes
– Exposes more rock
This picture shows prairie dogs burrowing into
the soil. Note the small rocks that are now
exposed.
…by grinding of rocks (abrasion)

Caused by wind, running water, waves, and
gravity

Rocks pushed together, causing pieces to
chip away
See how the wind has weathered this rock?
Another example of abrasion – running water
How can ice wedging break
rocks?

Water expands when it freezes. Liquid
water seeps into rock cracks and freezes.
…by ice wedging

Water gets into cracks
and freezes
– Remember, water
EXPANDS when it
freezes
– Causes cracks to get
bigger
Another picture of ice
wedging
Chemical Weathering
What is chemical weathering?

breakdown of rock through changes in its
chemical makeup.
– breaks down or weakens the rock
– More rapid in warm, wet climates
…by carbonation

Carbon dioxide + water =
carbonic acid
– Carbonic acid reacts with
minerals (like calcite)

Rocks (like limestone) can
be entirely dissolved, leaving
extensive caverns
– Can cause massive damage
to structures above ground
(ex: creating sinkholes)
…by oxidation



Oxygen + iron = iron
oxide
Iron oxide + water =
rust
If you compare a rusty
nail to a regular nail,
the unweathered nail is
much stronger.
…by acids

From plants (when it
decays)

Acid rain
– Normal rain is pH 6.2
– Sometimes rain can be
at a pH of 4 due to
pollution, factories,
and coal burning plants
True or False

Ice wedging occurs because of animals.
True or False

Weathering is the process where rock is
broken down.
True or False

Mechanical weathering creates rocks with
new chemicals.
True or False

Animals that dig tunnels do not help to
break down rocks.
True or False

Abrasion is the grinding of rocks against
other rocks.