Weathering of minerals at Clark Creek in Mississippi.
What is weathering?
Weathering is
the chemical alteration and physical breakdown of rock during exposure
to the atmosphere, hydrosphere, and biosphere. As a result of weathering,
the Earth is everywhere covered by an irregular blanker of loose rock debris
or soil.
There are two types of weathering, both of which occur
at Clark Creek.
First there is Chemical Weathering,
that is the decomposition of rocks and minerals as chemical reactions transform
them into new chemical combinations that are stable at or near the Earth's
surface.
Some of the photos to the left from Clark Creek illustrate
chemical weathering. In picture 1, oxidation has taken place. The
outer (cream) layer formed from the inner (blue) layer as oxygen from the
atmosphere caused the ferrous iron in the inner layer to change to ferric
iron..In picture 2, you can see red splotches in the wall of sedimentary
rock. The red areas are actually deposits of an iron oxide mineral called
hematite.
The other type of weathering is Physical
Weathering, that is the disintegration (physical
breakup) of rocks. The two processes generally work hand in hand, and their
effects are inseparably blended.
Plant roots (Picture 3) have grown into sedimentary
rock and caused cracks to form. Ultimately, the wedging action of the roots
may cause some of the wall to collapse, exposing the inner rock. This type
of weathering was seen all over the Clark Creek area.
Below is an outline of the different processes involved
in weathering.
I. PHYSICAL WEATHERING
A. Development of Joints
B. Crystal Growth
C. Frost Wedging
D. Effects of Heat (Spalls)
E. Plant Roots
II. CHEMICAL WEATHERING PROCESSES -
Named for the kind of chemical reaction taking place.
A. Hydrolysis
B. Leaching
C. Oxidation
D. Dissolution
III. FACTORS THAT INFLUENCE WEATHERING
A. Rock type and structure
B. Slope
C. Climate
D. Burrowing Animals
E. Time
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