Weathering of Rocks
All rocks which are exposed on the Earth's surface (high mountain peaks, deserts) are decomposed to a certain degree. The process of rock disintegration by the direct influence of local atmospheric conditions on the Earth's surface is called weathering. This phenomenon is often referred to in geology because weathering is an active process. It takes place in the upper layers of the Earth's crust.
The main cause of physical weathering is the change in temperature that takes place with the succession of day and night. This phenomenon can best be observed in the deserts and high mountains where the changes in temperature are common.
During the day under the influence of heat, rocks expand whereas at night they begin to contract. As rocks are generally composed of different minerals, their expansion and contraction do not occur uniformly. As a result of this rocks crack. At the beginning
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these cracks or fissures are hardly noticeable but gradually they become wider and deeper until the whole surface of rock is finally transformed into gravel, sand or dust.
In the regions of a moderate or cold climate, where the temperature in winter goes down to below 0 (zero), the decomposition of rocks is greatly facilitated by the action of water. When water freezes it increases in volume and develops enormous lateral pressure. Under the action of water, rocks decompose to pieces of varied forms and sizes.
The decomposition of rocks under the direct influence of heat and cold is called physical weathering.
Rocks are subjected not only to physical decomposition but also to chemical weathering, i.e. to the action of chemical agents, such as water, carbon dioxide and oxygen. In a general way, chemical weathering is an acid attack on the rocks of the Earth's crust, in particular an attack on the most abundant minerals quartz (sand) and aluminosilicates (clays). Only few minerals and rocks are resistant to the action of natural waters. The solvent action of water is stronger when it contains carbon dioxide. Water causes more complex and varied changes. With the participation of oxygen and carbon dioxide up to 90 per cent of rocks is transformed into soluble minerals, which are carried away by the waters.
Organisms and plants also take part in the disintegration of rocks. Certain marine organisms accelerate the destruction of rocks by making holes in them to live in. The action of plants can often be even more destructive. Their roots penetrate into the fissures of rocks and develop the lateral pressure which fractures and destroys rocks.
, . .
1. The process of sedimentation is called weathering.
2. The change in temperature causes physical weathering.
3. As a rule during the night rocks expand.
4. When freezing water decreases in volume and develops enor
mous lateral pressure.
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5. The decomposition of rocks is due to the influence of heat and
cold.
6. As a rule water contains_dissolved mineral substances.
7. The solvent action of water is stronger when it does not con
tain carbon dioxide.
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8. It should be noticed that the action of organisms and plants is
destructive.
9. Certain marine organisms accelerate the destruction of rocks.
33. :
1. What process ia called weathering?
2. What process is called physical weathering?
3. Where can the phenomenon of physical weathering be best
observed?
4. What process is called chemical weathering?
5. What substances can act as solvents?
6. Are all minerals and rocks resistant to the action of natural
waters or only few minerals and rocks can resist the action of water?
7. How do organisms act on the destruction of rocks?
34. )
:
1. the Earth's surface
2. to be composed of
different minerals
3. the expansion of rocks
4. changes in temperature
5. under the influence
of heat
6. weathering
7. destructive forces
8. a great number of
fractures
9. to penetrate into fissures
)
)
)
)
)
)
)
)
)
) :
1.
2.
3. -
4.
5.
6. (-.)
7.
8.
9.
) to facilitate the decomposition
of rocks
) to increase in volume
) to resist (smth)
r) rock pieces of varied (different) sizes
) to accelerate the process of
weathering
) to be subjected to decay
) to dissolve substances
) to develop lateral pressure
) certain organic substances
Unit 4
35. ) :
a, an, the.
this these, that those. my, his, her, its, our ..
Britain's deposits.
some, any, each, every. many, much, (a) little,
(a) few, a lot of .. two
countries, the third place. after, at, before, in, on, with ..
our country, the country, any country, each country, many countries, these countries, a small country, whose country, two big countries;
the discovery, after the discovery, each discovery, such discoveries, what discovery, few discoveries, a new discovery
) , , :
their study they study; the use we use; the increase they increase; coal output decrease coal output decreases; the last lectures the lectures last; this place it places; the raw material bases the country bases its economy on...
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36. , :
1. There are... causes of weathering, but... depends on the
change in temperature, (many, much)
2. As is known, only... minerals and rocks are resistant to the
action of natural waters, (little, few)
3. The roots of plants developed... pressure which did not frac
ture overlaying rocks, (little, few)
4. A new geological map of the region will appear in a... years.
(little, few)
5.... minerals undergo changes. They have already undergone...
transformation, (, much)
6. Now there are... sources of energy as important as atomic
energy, (little, few)
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