Transcript Weathering - section 14.1

The Changing Earth
Chapter Fourteen: Weathering
and Erosion
• 14.1 Weathering
• 14.2 Erosion
• 14.3 Rivers Shape the Land
Investigation 14A
Water Systems
• How does running water shape rivers and
landscapes?
14.1 Weathering
• The process of
breaking down rock
is called weathering.
• The Sun and the
Earth’s internal
forces create the
energy needed for
weathering to occur.
14.1 Weathering
• The Smokey Mountains are older than the
Rocky Mountains.
How do these two mountain ranges differ?
14.1 Weathering
•
At one time, the Smokies may have been as
tall as the Rockies and also had sharp peaks.
How long did the weathering of the Smokies take?
14.1 Ways weathering occurs
•
Mechanical
(physical) weathering
occurs when forces
(such as water) break
or chip rocks and
minerals into smaller
pieces without
changing their
composition.
14.1 Ways weathering occurs
• Rock is also
reduced to smaller
pieces by chemical
reactions between
water and rock
grains. This
process is called
chemical
weathering.
14.1 Agents of mechanical
weathering
•
•
Weathering occurs quickly when running water
knocks rocks against each other.
Water has the greatest effect on the rate at
which rocks weather.
14.1 Agents of mechanical
weathering
• Frost wedging is a
type of mechanical
weathering that splits
apart rock slowly as
water freezes.
• When ice expands and
water contracts, it
causes more cracks in
rock.
14.1 Agents of mechanical
weathering
• Plants cause
mechanical weathering
when their roots grow
into small cracks in a
rock (root wedging.)
• Animals cause
mechanical weathering
when they dig into soil
or burrow underground.
14.1 Agents of mechanical
weathering
• Exfoliation is a
mechanical
weathering process
that results in rock
layers peeling away
as they expand or
contract.
14.1 Agents of mechanical
weathering
• Even wind is a
weathering agent.
• Wind-blown sand
chips away tiny bits
of rock from the
surface of exposed
rock.
14.1 Chemical weathering
• Moss and lichens
on rocks will
eventually cause
them to break down
because of
chemicals they
release.
14.1 Chemical weathering
• Acid rain is a
form of chemical
weathering
where the acids
in the rain react
with the minerals
in rock to
change its
composition.
14.1 Factors that
affect weathering
• Weathering is fastest in hot, humid climates
(like a rainforest.)
• Running water speeds up mechanical
weathering and chemical weathering.
• The kind of minerals found in a rock affects
how fast it weathers (the calcite in marble
causes it to weather faster than granite.)