Weathering and Mass Movement

Question 1

What is a cliff?

Answer 1

A steep high rock face formed by weathering and erosion.

Question 2

What is weathering?

Answer 2

The weakening or decay of rocks in their original place on, or close to, the ground surface.

Question 3

What are the three types of weathering?

Answer 3

Mechanical, chemical and biological.

Question 4

What are the mechanical weathering processes?

Answer 4

Freeze-thaw weathering and salt weathering.

Question 5

What is the chemical weathering process?

Answer 5

Carbonation.

Question 6

What are the biological weathering processes?

Answer 6

Flora and fauna.

Question 7

By how much does water expand when it freezes?

Answer 7

9%.

Question 8

What is scree?

Answer 8

Piles of rock fragments at the foot of cliffs.

Question 9

What does sea water leave behind when it evaporates?

Answer 9

Salt crystals.

Question 10

How do salt crystals put pressure on the rock?

Answer 10

They grow.

Question 11

What are pores?

Answer 11

Cracks and holes in rock.

Question 12

Name two alkaline rocks.

Answer 12

Limestone and chalk.

Question 13

What does rainwater absorb from the air?

Answer 13

CO2.

Question 14

What does rainwater turn after absorbing CO2 from the air?

Answer 14

Slightly acidic.

Question 15

What results in a chemical reaction in carbonation?

Answer 15

The contact with the alkaline rocks (chalk or limestone) and the acidic rainwater.

Question 16

What grows in pores and faults in the rock?

Answer 16

Roots of plants.

Question 17

What does roots of plants growing in pores in the rock result in?

Answer 17

The cracks expanding, splitting the rock.

Question 18

Give an example of an animal that may burrow into weak rock (e.g., sand).

Answer 18

Rabbits.

Question 19

What is erosion?

Answer 19

Wearing away and removal of material by a moving force, such as a breaking wave.​

Question 20

What does impermeable mean?

Answer 20

Resistant material that is Impossible for water to soak into.

Question 21

What does permeable mean?

Answer 21

Less resistant material that is possible for water to soak through.

Question 22

What does saturate mean?

Answer 22

When the small pores and cracks are filled with water and cannot hold anymore water.

Question 23

What is the base?

Answer 23

The bottom of the cliff.

Question 24

What is mass movement?

Answer 24

Downward movement of weathered material under the force of gravitational pull.

Question 25

Name the 5 erosional processes.

Answer 25

Solution, attrition, abrasion, corrasion, hydraulic action.

Question 26

What is solution?

Answer 26

The dissolving of soluble chemicals in rocks e.g. limestone.​

Question 27

What is hydraulic action?

Answer 27

The power of the waves as they smash onto a cliff. Trapped air is forced into holes and cracks in the rock eventually causing the rock to break apart. The explosive force of trapped air operating in a crack is called cavitation.

Question 28

What is attrition?

Answer 28

Rock fragments carried by the sea knock against one another causing them to become smaller and rounder.

Question 29

What is corrasion?

Answer 29

Fragments of rock are picked up and hurled by the sea at a cliff. The rocks act like tools scraping and gouging to erode the rock.

Question 30

What is abrasion?

Answer 30

The is the ‘sandpapering’ effect of pebbles grinding over a rocky platform often causing it to become smooth.

Question 31

Explain the process of freeze-thaw weathering.

Answer 31

Water collects in cracks or holes (pores) in the rock. At night this water freezes and expands and makes the cracks in the rock bigger. When the temperature rises and the ice thaws (melts), water will seep deeper into the rock. After repeated freezing and thawing, fragments on rock may break off and fall to the foot of the cliff as scree.

Question 32

Explain the process of salt weathering.

Answer 32

Seawater contains salt. When the water evaporates it leaves behind salt crystals. In cracks and holes (pores) these salt crystals grow and expand. This puts pressure on the rocks and flakes may eventually break off.

Question 33

Explain the process of carbonation.

Answer 33

Rainwater absorbs CO² from the air and becomes slightly acidic. Contact with alkaline rocks (chalk and limestone) produces a chemical reaction causing the rocks to slightly dissolve.

Question 34

Explain the process of rotational slip.

Answer 34

Rotational slip forms from soft boulder clay, left behind by melting glaciers. The soft, less resistant boulder clay is eroded through hydraulic action, where the power of the waves smashes onto the cliff. As a result, trapped air is forced into holes and cracks in the rock. The pressure builds causing the rock to break. Abrasion also erodes to the soft boulder clay by pebbles grinding over a rocky platform often causing it to become smooth. Prolonged rainfall saturates the permeable boulder clay which increases its weight. Due to gravitational pull and the increased weight of the saturated boulder clay, the soft boulder clay slumps. The debris on the beach is then eroded by the sea, leaving the cliff exposed once more.

Question 35

Explain the process of a landslide.

Answer 35

Landslides form in areas of more resistant cliff material. More resistant rock is mainly eroded by the waves and not weathering processes. This causes erosion at the base of the cliff, from hydraulic action where the force of the waves causes air to be trapped in the cracks and pressure causes rocks to break. In addition, abrasion causes pebbles to be grinded along the base of the cliff. This creates a wave-cut notch in the base of the cliff. As the notch increases in size, the weight of the cliffs above becomes too much to support, leading to a landslide. This material will provide temporary protection for the cliff behind. However, once the sea has removed it, this process will occur again. Wave-cut platforms will be created where cliffs are made of more resistant material.

Question 36

Explain the process of a rockfall.

Answer 36

A rockfall involves rock fragments breaking away from the cliff face, often due to freeze-thaw weathering. Water collects in the crack or pores in the rock. At night this water freezes and expands and makes the cracks bigger. When the temperature rises from the morning, and the ice thaws (melts), water will seep deeper into the rock. After repeated freezing and thawing, fragments of rock may break off and fall to the foot of the cliff as scree.

Question 37

Explain the process of a mudslide.

Answer 37

Mudslides form from boulder clay. The less resistant, permeable boulder clay becomes saturated from prolonged rainfall. Due to gravitational pull and the increased weight of the saturated rock, the boulder clay slides. Sliding is faster than slumping, and mudslides occur at steeper cliffs.