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blasted in search of minerals or for construction, the impact of humans is particularly
noticeable.
There are numerous ways that organisms play a role in chemical weathering. For
example, plant roots, fungi, and lichens that occupy fractures or may encrust a rock
produce acids that promote decomposition. Moreover, some bacteria are capable of
extracting compounds from minerals and using the energy from the compound’s
chemical bonds to supply their life needs. These primitive “mineral-eating” life forms
can live at depths as great as a few kilometers.

Task 3. Compare and discuss the most important types of mechanical
weathering:
 frost wedging;
 salt crystal growth;
 sheeting;
 biological activity.

Task 4. Look at Figure 9.2. What type of mechanical weathering does it
illustrate? What made you come to that conclusion?

Individual work

Task 1. Read the text and translate it into Ukrainian (in written form).
Build up a list of key terms to the text.

Chemical Weathering
Chemical weathering involves the complex processes that break down rock
components
and internal structures of minerals. Such processes convert the constituents to new
minerals or release them to the surrounding environment. During this transformation,
the original rock decomposes into substances that are stable in the surface environment.
Consequently, the products of chemical weathering will remain essentially unchanged
as long as they remain in an environment similar to the one in which they formed.
Water and Carbonic Acid. Water is by far the most important agent of chemical
weathering. Although pure water is nonreactive, a small amount of dissolved material is
generally all that is needed to activate it. Oxygen dissolved in water will oxidize some
materials. When rocks containing iron-rich minerals oxidize, a yellow to reddish-brown
rust will appear on the surface.
The weathering of potassium feldspar generates a residual clay mineral, a
soluble salt (potassium bicarbonate), and some silica, which enters into solution. Quartz,
the other main component of granite, is very resistant to chemical weathering; it
remains substantially unaltered when attacked by weak acidic solutions. As a result,
when granite weathers, the feldspar crystals dull and slowly turn to clay, releasing the
once-interlocked quartz grains, which still retain their fresh, glassy appearance.
Although some quartz remains in the soil, much is eventually transported to the sea or
to other sites of deposition, where it becomes the main constituent of such features as
sandy beaches and sand dunes. In time these quartz grains may become lithified to form
the sedimentary rock sandstone.
Weathering of Silicate Minerals. Silicate minerals make up most of Earth’s
crust and that these minerals are composed essentially of only eight elements. When
chemically weathered, silicate minerals yield sodium, calcium, potassium, and
magnesium ions that form soluble products, which may be removed by groundwater.

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