2B.6 subaerial processes

Question 1

what are the three types of weathering

Answer 1

biological, chemical, mechanical

Question 2

what is weathering

Answer 2

the breakdown or decay of rocks in situ- near the earth’s surface without any movement of the material involved.

Question 3

what are the 2 types of mechanical weathering?

Answer 3

freeze thaw weathering
salt crystallisation

Question 4

what is freeze thaw weathering

Answer 4

mechanical weathering type- when water enters a crack or joint in the rock when it rains. And then freezes, the water expands by 10% which exerts pressure and widens the crack. Fragments eventually break off forming scree

Question 5

what is salt crystallisation weathering?

Answer 5

mechanical weathering where salt water evaporates leaving salt crystals behind. these can grow and exert pressure on the rock so it breaks up.

Question 6

what are the three types of chemical weathering

Answer 6

carbonation
hydrolysis
oxidation

Question 7

what is carbonation weathering

Answer 7

chemical weathering when rain absorbs carbon dioxide from the air to form weak carbonic acid. this reacts with calcium carbonate in rocks like limestone and chalk to form calcium carbonate which is easily dissolved

Question 8

what is hydrolysis weathering?

Answer 8

chemical weathering which occurs when water reacts with minerals in the rock causing the chemical composition to change and become more unstable

Question 9

what is oxidation weathering?

Answer 9

chemical weathering when oxygen reacts with minerals like calcium and magnesium to form iron oxide

Question 10

what are two types of biological weathering?

Answer 10

plant roots and rock boring

Question 11

outline plant roots weathering

Answer 11

biological weathering when plant roots start to grow into small cracks in cliff face. they widen as the roots grow thicker, this breaks up the rock

Question 12

outline rock boring weathering

Answer 12

biological weathering where animals can move rocks to the surface where they are open to weathering. animals like limpets also secrete chemicals causing rocks to dissolve. birds and animals dig burrows into cliffs. water which runs through decaying vegetation becomes acidic and increases chemical weathering

Question 13

what is mass movement?

Answer 13

when material is moved due to gravity. the downslope movement of rocks and soil from the cliff top is under the influence of gravity. can provide a sediment input to the coastal system

Question 14

what is rock fall

Answer 14

occurs when strong jointed and steep rock faces are exposed to mechanical weathering. on slopes over 40 degrees. material once broken away from the source forms scree or talus at slope foot.

Question 15

what is a rock debris slide

Answer 15

rocks that are jointed or have bedding planes roughly parallel to the slope are susceptible. increase in water can reduce friction causing sliding. in a rock or landslide slabs of rock can slide over underlying rocks along a slide or slip plane.

Question 16

what is topple

Answer 16

when pieces of rock or cliff face fall forward as large blocks due to forward rotation down a slope. occurs around an axis at the base of the block of rock.

Question 17

what is translational slide

Answer 17

a downslope movement of material that occurs along a distinctive planar surface of weakness such as a fault, joint, or bedding plane.

Question 18

what is rotational slide / slumping

Answer 18

when material moves down a concave cliff face making the material rotate backwards into the cliff as it slips down. occurs in saturates conditions, includes a rotational movement causing rotational scars and repeating slumping creating a terraced cliff profile.

Question 19

what is earth / mud flow

Answer 19

occurs when material behaves more like a liquid or fluid due to a high water content and unconsolidated material which causes slope material to lose cohesion and turn into slurry

Question 20

what is soil creep

Answer 20

slowest form, a continuous process of downhill movement of individual soil particles

Question 21

what is solifluction

Answer 21

between 5 and 100 cm annually. mainly in tundra areas where ground is frozen, the surface layer becomes saturates and flows over the frozen subsoil and rock.

Question 22

what does the type of mass movement depend on

Answer 22

• the angle of the slope
• the rock lithology and geology
• vegetation cover on cliff face
• saturation of ground

Question 23

what are the impacts of weathering and mass movement

Answer 23

loss of businesses from tourism
loss of land
land unstable or unsafe
building collapse
injury
death

Question 24

what landforms are created by mass movement

Answer 24

rotational scars
talus scree slopes
terraced cliff profiles

Question 25

what is a rotational scar

Answer 25

a subaerial landform which looks like a fresh curved unweathered and unvegetated rock surface on a cliff face. left behind from rotational slumping. when heavy rain is absorbed by unconsolidated material it makes up the cliff, the cliff face gets heavier and unstable so it separates from the material behind at a rain-lubricated slip plane. surface of rupture is curved concavely upward.

Question 26

what is a talus scree slop

Answer 26

sub aerial landform, talus is the unstable steep mountain slope composed of rock fragments and other debris. it is material that has accumulated at the base of a projecting mass of rock, or talus slope

Question 27

what is a terraced cliff profile?

Answer 27

a subaerial landform where the cliff profile is stepped due to lithology or rock fractures.

Question 28

what is the ONLY case study for 2b.6?

Answer 28

west bay dorset

Question 29

what is the geology of west bay dorset?

Answer 29

cliffs of weak sandstone, mudstone, and limestone layers. weak and easily eroded sedimentary rocks. concordant coast so has bays

Question 30

what subaerial processes occur at west bay dorset

Answer 30

weathering: freeze thaw, salt crystallisation, biological weathering mass movement: rock fall, landslides due to heavy rain in porous sandstone.

Question 31

what was the significant event at west bay dorset

Answer 31

August 2012 cliff collapse which killed a holidaymaker.