weathering and erosion

Question 1

define ‘erosion’:

Answer 1

wearing away and removal of material by a moving force (e.g. a wave)

Question 2

describe hydraulic action/power:

Answer 2

there are natural cracks in cliff faces, and when water is forced into the cracks, they compress trapped air, and the cracks widen. as the water rushes out again, this force and the force of the water may cause pieces of rock to chip off.

Question 3

describe abrasion:

Answer 3

sediment is carried by the water, and when waves hit the cliff face, the sediment is thrown against the rock, scraping fragments off, and slowly eroding it over time. the material acts as sandpaper, wearing away the seabed/cliff.

Question 4

describe solution (a.k.a. corrosion):

Answer 4

weak acids in seawater dissolve soluble rocks such as chalk and limestone.

Question 5

describe attrition:

Answer 5

loose sediment in the water is swirled around by the waves. because of this, the particles bash into each other, and over time, each pebble either breaks apart / becomes smooth, spherical and shiny.

Question 6

define ‘weathering’:

Answer 6

the wearing away of rocks in situ (where they are).

Question 7

describe chemical weathering:

Answer 7

the breaking down of rock, caused by a chemical composition change within that rock.
- rain is naturally acidic, so naturally rock will wear away over time. however, burning fossil fuels releases gases into the atmosphere, such as carbon dioxide. when the climate is warm and wet, this carbon dioxide can dissolve in rain to create a ‘carbonic acid’.
- the carbonic acid in the rainfall hits the rocks and dissolves the parts of the rocks made up of calcium carbonate.
- this also breaks down the rock.

Question 8

describe mechanical weathering (freeze thaw):

Answer 8

• chemical composition remains the same
  when it rains, water fills up the cracks in the rocks. during the night, it gets very cold, and water freezes, making it and the cracks expand. this occurs every night, until the crack is so wide that the rock splits apart.
• can cause significant erosion of coast lines over time.

Question 9

describe mechanical weathering (onion skin):

Answer 9

• chemical composition remains the same
  often occurs in areas of great temperature change. rocks heat during the day, causing them to expand. when the temp. falls at night, the rock will contract. this expansion and contraction applies stress to the outer rock layers, causing them to split apart.

Question 10

describe biological weathering:

Answer 10

sometimes a seed of a plant will land in a crack in a rock and begin to grow. as it grows, its roots will get bigger and longer, and the roots will force a crack in the rock to grow wider. eventually the root will split the rock apart.
- bird nests on the side of cliff faces can also degrade the rock.