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Name:______________________
CP Geoscience: Mrs. Zeiders
Date:_________________
Period:_______________
Earth Revealed: Weathering and Soils
Source: www.learner.org
1. Most rocks are formed deep beneath the Earth’s surface or on the ocean floor. Tectonic
activity, such as uplift, mountain building or falling sea levels bring these rocks from their
environment of formation up to the Earth’s surface. There rocks are changed into a form that is
stable under these new conditions by a process called weathering.
2. Weathering occurs in tow fundamentally different ways: the first of these involves the
breaking of rock into fragments and individual mineral crystals. The physical fragmentation of
rock is known as mechanical weathering.
Some examples of mechanical weathering include: unloading, frost wedging, biological activity.
The second type of weathering is chemical weathering.
3. Chemical and mechanical weathering are interrelated: mechanical weathering increases the
amount of exposed surface area, which hastens chemical weathering of the entire rock.
4. The main agents of chemical weathering are water in the ground and moisture in the air.
5. Unlike mechanical weathering, chemical weathering destroys or changes the composition of
the rock. A good example is rust (oxidation).
6. The degree of weathering is related to the amount of water in the natural environment.
7. The rate that a rock will weather is primarily controlled by the climate.
8. If you have a very wet, moist climate, you will have a lot more chemical weathering. In
addition to water, temperature is important because warmer temperatures mean faster
chemical reactions.
Name:______________________
CP Geoscience: Mrs. Zeiders
Date:_________________
Period:_______________
9. Most minerals form at temperatures and pressures very different from those at the Earth’s
surface. The minerals most unstable at the Earth’s surface are those that weather the fastest.
10. Minerals that are the most stable and weather the least are those that formed, initially, at
the lowest temperatures.
11. Weathering is essentially a process of destruction involving the physical and chemical
breakdown of the parent rock.
12. Burning of fossil fuels releases gases than combine chemically with rain water, in some
cases creating solutions that are hundreds of times more acidic than natural rain alone. The
effect of this creates a global-scale environmental problem known as acid rain.
13. Although weathering is fundamentally a process of destruction, it has the beneficial effect
of breaking rocks down into soil, which is essential to life!
14. Soils are formed as a result of both chemical and mechanical weathering.
15. The decomposition of plant life produces rich organic matter known as humus.
16. As soil matures, if forms into several different layers or Horizons. The “A” Horizon is the
loamy topsoil where most plant humus is derived. Rainwater washes through this horizon
down to the “B” Horizon where the leached material accumulates. The “C” Horizon is the
bottommost layer where the underlying bedrock is partially disintegrated and decomposed.
17. The nature of a soil is determined partly by what sort of parent rock it develops from.
Climate and time also play important roles in the evolution of soils. (Climate is most
important.)
Name:______________________
CP Geoscience: Mrs. Zeiders
Date:_________________
Period:_______________
18. Fertile soil doesn’t come into existence quickly. It took about 15,000 years to develop a
layer less than one (1) meter thick in the soil example from the American Midwest. Whereas,
thick layers of soils in tropical climates can develop in only a few thousand years.
19. List at least three factors that cause soil erosion.

Overgrazing;

Construction;

Deforestation; and

Poor soils management
20. List at least three ways in which soil erosion can be mitigated (lessened).

Windbreaks;

Routine soil tilling; and

Irrigation management.