WEATHERING

Question 2

What is meant by weathering?

Answer 2

The breakdown of rock by mechanical, physical and biological forces that do not remove it (in situ).

Question 3

What is meant by physical weathering?

Answer 3

This involves the disintegration or breaking of the rock into smaller pieces with no chemical change in their composition.

Question 4

What is meant by chemical weathering?

Answer 4

This involves the decomposition of rocks by changing their chemical composition.

Question 5

List the the main types of physical weathering.

Answer 5

Freeze - thaw, exfoliation and granular disintegration.

Question 6

List the two main types of chemical weathering.

Answer 6

Carbonation and oxidation.

Question 7

What is meant by biological weathering?

Answer 7

Where plants and animals contribute towards physical and chemical weathering.

Question 8

Explain how carbonation weathering may help to break down limestone.

Answer 8

Rainwater combines with carbon dioxide in the air to form carbonic acid. This attacks the rock surface as well as soaking into the joints and bedding planes. The carbonic acid reacts with rocks such as limestone to make calcium bicarbonate. This is soluble and gets carried away in solution.

Question 9

Explain how oxidation weathering may help to break down rock.

Answer 9

Oxygen in the air combines with metal, especially iron in the rocks. This reaction expands and weakens the original rock mineral which breaks down easily as rust. A red - brown colour on the rock surface indicates that oxidation has taken place.

Question 10

Explain how freeze - thaw weathering may break down rock.

Answer 10

Water gets into the rock through vertical cracks (joints) and horizontal bedding planes that separate the layers of the rock. When the temperature drops below zero the water freezes it expands by 9% in volume. This freeze thaw cycle puts pressure on the rocks which break up by frost shattering.

Question 11

Explain how exfoliation weathering may help break down rock.

Answer 11

In hot conditions the surface of the rock is heated and expands. But in the cool of the night it contracts again. This creates stress in the rock, which breaks up slowly in layers.

Question 12

Explain how biological weathering may help to break down rock.

Answer 12

Plants use their roots to force apart layers of rock by moving along bedding planes, joints or cracks, resulting in the mechanical breakdown of rocks. Plants can also release chemicals such as carbonic acid break chemically breaks down rocks.

Question 13

Describe the climatic conditions that will allow freeze - thaw to take place.

Answer 13

High levels of precipitation and temperatures that fluctuate above and below freezing.

Question 14

Describe the climatic conditions that will allow exfoliation to take place.

Answer 14

Very high daytime temperature and low nighttime temperatures.

Question 15

Describe the climatic conditions that will allow carbonation to take place.

Answer 15

High levels of precipitation and warm temperatures.

Question 16

Describe the climatic conditions that will allow oxidation to take place.

Answer 16

High levels of precipitation and warm temperatures.

Question 17

Explain why the rate of biological weathering in the UK will be greater in the summer .

Answer 17

Higher temperatures in te summer allow plants to grow therefore their roots expand. Carbonic acid released by plants reacts faster with the chemicals within rocks in warmer conditions.

Question 18

Define the term scree.

Answer 18

An accumulation of small pieces of angular rocks at the bottom of a slope or cliff.

Question 19

Where does scree usually accumulate.

Answer 19

It accumulates in wedges at the base of steep cliffs where rock is exposed to the elements.

Question 20

Explain how scree is formed.

Answer 20

The process of freeze thaw or exfoliation breaks down the exposed rock on the cliff face. This then falls under gravity to the base of the cliff where it accumulates.

Question 21

Describe the climatic conditions found in humid tropical area.

Answer 21

Warm temperatures above 20 degrees centigrade and precipitation above 1500mm per year.

Question 22

Describe the conditions found in a temperate region.

Answer 22

Temperatures that fluctuate above and below zero degrees centigrade and precipitation below 750mm per year.

Question 23

Explain why in humid tropical areas the rate of chemical weathering has little annual variation.

Answer 23

There is little change in temperature and the amount of rainfall that falls each month. Therefore, chemical reactions happen at the same rate all year.

Question 24

Explain why weathering processes are more rapid in humid tropical regions than in temperate regions.

Answer 24

Tropical regions have higher temperatures and higher levels of rainfall which encourages chemical weathering. The rate of chemical reactions doubles with every 10 degree centigrade rise in temperature. Conditions encourage rapid plant growth which means there is more biological weathering. Also dead plants decay quickly releasing large amounts of carbonic acid.

Question 25

Which type of weathering will dominate in tropical desert regions?

Answer 25

Physical weathering such as exfoliation.

Question 26

Which type of weathering will dominate in tropical rainforests.

Answer 26

Chemical weathering such as oxidation and biological weathering.

Question 27

What type of weathering will dominate in temperate mountainous areas?

Answer 27

Physical weathering such as freeze - thaw.

Question 28

What is the chemical formula for carbonation weathering.

Answer 28

CO2 + H2O -> H2CO3
carbon dioxide + water -> carbonic acid

H2CO3 + CaCO3 -> Ca(HCO3)2
carbonic acid + calcium carbonate -> calcium bicarbonate

Question 29

Give two reasons to explain why sandstone rock with many bedding planes and joints will weather quickly.

Answer 29

It allows roots to easily penetrate the rock and force it apart. Also water can run into the rock allowing freeze - thaw weathering to take place.

Question 30

What is meant by diurnal temperature range?

Answer 30

The difference between the maximum day time temperature and the lowest night time temperature.