Weathering (ch.08)

Question 1

Mechanical Weathering

Answer 1

rocks are physically broken down by wind, frost or rain

Question 2

Chemical Weathering

Answer 2

rocks are dissolved gradually over time

Question 3

Biological Weathering

Answer 3

rocks broken down by animal or human activity

Animals = burrowing in the ground. The soil is removed and new rock is exposed to weathering.

Trees = grow through boulders, splitting them and exposing them to weathering

Humans =

1. mining exposes rock for weathering
2. carbon dioxide pollution can lead to the formation of acid rain and greater chemical weathering of rocks.

Question 4

Denudation

Answer 4

Weathering and Erosion

Question 5

Give 1 example of mechanical weathering. Include a diagram and an example.

Answer 5

Freeze-thaw action
Freeze-thaw action occurs when rocks break up because of repeated freezing of water and thawing of ice in upland areas.

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Upland areas tend to receive more rain than lowland areas. During the day, rainwater gathers in cracks in rocks high up in mountains.

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At night, when the temperature drops below 0C, the water in the crack freezes and expands by about 10%. The expansion of the ice places pressure on the cracks in the rock, causing them to widen.

The following day when temperatures rise and the water thaws, it lies deeper in the cracks. The next time the water freezes, the joints widen even more.

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Over thousands of years the constant expansion and contraction of the crack weakens the rock and causes it to break off and collapse into smaller pieces of rock called scree or talus. The scree travels down the side of the mountain.

e.g. the Great Sugarloaf, Co. Wicklow

Question 6

Give 1 example of chemical weathering. Include a diagram and an example.

Answer 6

Carbonation.

Carbonation occurs in limestone landscapes, where bare limestone is exposed to the rain. These areas are known as karst landscapes. Rainwater mixes with carbon dioxide in the atmosphere forming a weak carbonic acid. This acid reacts with calcium carbonate in the limestone, causing the rock to slowly dissolve. Carbonation has created many spectacular features on the surface and underground.

e.g. The Burren, Co. Clare.

Question 7

Give 1 example of a surface feature formed by chemical weathering. Include a diagram and an example.

Answer 7

Clints and Grikes
Clints and Grikes are formed in limestone areas as a result of Carbonation.

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Rainwater mixes with carbon dioxide in the atmosphere to form a weak carbonic acid.
The acid reacts with the calcium carbonate in the limestone, causing it to slowly dissolve.

The rainwater trickles into the cracks in the limestone. Carbonation causes the cracks to get wider and deeper. These are now called grikes.

The limestone that is left sticking up between the grikes is called a clint.
Clints and grikes together are known as limestone pavement.

e.g. Kilfenora, Co. Clare.

Question 8

Give 1 example of an underground feature formed by chemical weathering. Include a diagram and an example.

Answer 8

Columns
Columns form in underground limestone areas when a stalactite and a stalagmite grow towards each other and eventually join up.

Question 9

Draw a diagram of an underground limestone area

Answer 9

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