Unit 7 Day 1
Weathering
Mechanical Weathering
Weathering
Mechanical weathering (also called
) is the process by which rocks and
minerals break down into
Mechanical weathering does not change the
composition, only the
the rock
and
of
SOL 8 The student will investigate and understand
geologic processes…... Key concepts include
b. processes (…weathering, erosion, deposition, and
sedimentation) and their resulting features.
Objective
1 Summarize weathering as the process by which rocks
are broken down by the action of water, air, and
organisms.
2 Distinguish between physical (
) and
weathering.
3 Recognize factors that affect the rate of weathering.
Enduring Understandings
Weathering, erosion, and deposition are interrelated
processes that form a cycle of forces that
and
the Earth’s surface.
Weathering
Immediately after the first rocks on earth crystallized
billions of years ago the process of weathering began to
take effect to break them down again.
Weathering is the process by which rocks on or near
the Earths surface
and
Erosion is the
and
weathered material from one location to another.
–

plays a significant role in
mechanical weathering.
As water
it
and
will crack rocks

is another factor in mechanical
weathering as overlying layers of rock are removed the
pressure is reduced and the exposed surface will expand
and crack

is the process by which the outer
layers of rocks are stripped off
of
Materials are transported by moving
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Chemical Weathering
Factors Affecting the rate of
Weathering
Exposed rocks can undergo changes in their
as well and result in the formation
of new minerals and the release of
substances.
Water,
Natural weathering is a very
process.
Certain conditions and interactions can accelerate or slow
the process significantly

is a major influence. The
interaction between temperature and precipitation has the
greatest effect on a region’s rate of weathering
and acids are
common agents


is the chemical reaction of
weathering rates are highest in cool, areas
where water undergoes repeated
and
oxygen with other substances
Carbon Dioxide combines with water in the
atmosphere to form
the surface as precipitation
that falls to
Carbonic acid reacts with minerals such as calcite in
limestone and marble to

weathering rates are highest in
areas with warm temperatures and abundant
and heavy vegetation

and composition also affects the
weathering rate. Some are quite resilient (Quartz) while
some are easily broken down (Talc)

interacts with both
mechanical and physical weathering as pieces break up
through mechanical weathering more surface area is
for chemical weathering

is the shape and slope of the
Earth’s surface. Materials that lie on steep slopes are
more likely to move and expose even more surface area

(acid rain) is
another agent of chemical weathering caused by the
oxidation of sulfur dioxide and nitrogen oxides released
into the atmosphere by human activities
These gasses combine with water and oxygen in the
atmosphere to form
.
and nitric
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