2b - coastal landscapes & change

Question 1

COASTAL LANDSCAPES - describe what is meant by the ‘littoral zone’

Answer 1

• a series of sub-zones to represent the features of the wider coastline from sea to land

Question 2

what does the littoral zone include?

Answer 2

• includes 4 key sub-zones : offshore, nearshore, foreshore and backshore

Question 3

when does the littoral zone reach dynamic equilibrium?

Answer 3

• when there is a balance between inputs and outputs

Question 4

state the inputs and outputs of the littoral zone

Answer 4

• sediment is the key input AND output of the system and is determined by :
  —> INPUTS - the action of waves, currents and wind
  —> OUTPUTS - washed into the sea by erosion

Question 5

what are high energy coasts characterised by?

Answer 5

• destructive waves
• long fetches
• high rates of erosion
• caves
• arches
• stacks & stumps
• cliffs & wave-cut platforms

Question 6

what are low energy coastlines characterised by?

Answer 6

• constructive waves
• shorter fetches
• higher rates of deposition
• spits & bars
• beaches
• sand dunes & salt marshes

Question 7

GEOLOGICAL STRUCTURE - describe concordant coastlines

Answer 7

• have alternating bands of hard and soft rock parallel to the coast

Question 8

describe discordant coastlines

Answer 8

• have alternating bands of hard and soft rock at right angles to the coast
  —> erosional landforms are more common on discordant coastlines because erosion happens at different rates along their length

Question 9

how is Dorset an example of a discordant coast?

Answer 9

• in Dorset, the coastline consists of Portland limestone and Greensands
• the Greensands is less resistant to erosional processes, and so retreats at a faster rate than the Portland limestone
• this has resulted in the creation of a bay and headlands

Question 10

COASTAL MORPHOLOGY - how are Dalmation coasts formed?

Answer 10

• concordant coastlines, also referred to as Pacific coasts, lead to the formation of Dalmation coasts
• Dalmation coasts are made up of offshore islands and coastal inlets running parallel to the coastline
  —> EXAMPLE : Lulworth Cove, located on the south-west Dorset coastline.
  —> here, the more resistant rock (eg limestone) acts as a barrier to protect the less resistant rock

Question 11

what landforms form at Atlantic coasts?

Answer 11

• headlands and bays often form on discordant coastlines (also referred to as Atlantic coasts)
• as the faster eroding, less resistant rock retreats (eg the clays at Swanage Bay), this leaves behind the more resistant rock as headlands

Question 12

how are headland features formed?

Answer 12

—> on discordant coastlines, the retreating, less resistant rock and the exposed resistant rocks cause a change in the shape of the coastline. This leads to WAVE REFRACTION.
—> this change in the way in which waves approach the coastline can cause an increase in the rate of erosion on the headlands
—> this leads to the formation of headland features like caves, arches, stacks and stumps.

Question 13

GEOLOGICAL STRUCTURE - what causes the geological structure of rocks?

Answer 13

• the geological structure of rocks (the formation of joints, the angle of the dip, faulting and folding) is caused by the deformation and stress placed on them from tectonic processes

Question 14

why are rocks like sedimentary more susceptible to erosion and weathering?

Answer 14

• these are rocks with the presence of more joints and faults
• this is because these processes exert forces on the weaknesses found in the layers of the rocks

Question 15

define the term ‘dip’

Answer 15

• the angle of the rock layer which forms the horizontal bedding plane
• rocks can dip either towards the land or towards the sea

Question 16

how is a gentler cliff profile created?

Answer 16

• bedding planes that dip towards the sea create these
• BUT these cliffs are vulnerable to mass movement processes, like rockfalls

Question 17

how is a steeper cliff profile created?

Answer 17

• bedding planes that dip towards the land tend to create these
• BUT, these cliffs are more vulnerable to erosion processes, like hydraulic action and abrasion

Question 18

BEDROCK LITHOLOGY - what does this refer to?

Answer 18

• the physical properties of different rocks
• the existence of sedimentary, igneous and metamorphic rocks affects the rate of recession along a coastline

Question 19

how are igneous rocks formed?

Answer 19

• igneous rocks, such as basalt and granite, form from the crystallisation of magma.
• they are more resistant to erosion and weathering

Question 20

why are igneous rocks more resistant to erosion and weathering?

Answer 20

• igneous rocks contain crystals which increase the strength of the rocks and reduce the number of lines of weaknesses that would be exploited by physical processes

Question 21

state the difference between intrusive and extrusive igneous rock

Answer 21

• intrusive igneous rock is formed from magma inside the Earth, whereas extrusive igneous rock is formed when magma escapes through vents on the Earth’s surface
• the average rate of erosion of igneous rock is 0.1-0.5cm per year

Question 22

how are sedimentary rocks formed?

Answer 22

• sedimentary rocks, such as limestone and sandstone, form from the build up, compacting and hardening of sediments into layers over time by lithification

Question 23

why are limestone and chalk more susceptible to erosion and weathering?

Answer 23

• sedimentary rocks that have been formed in a shorter geological time scale tend to be more susceptible and erode at a faster rate compared with those formed over a longer geological time
  —> the average rate of erosion of sedimentary rocks is 2-6cm per year

Question 24

how is metamorphic rock formed?

Answer 24

• metamorphic rocks, such as slate and marble, are formed from the change in the structure of sedimentary and igneous rocks, caused by variations in heat and pressure
• the process of change is referred to as the rocks having been metamorphosed.

Question 25

how is marble an example of metamorphic rock?

Answer 25

• marble is an example of a metamorphic rock that has been formed from the changing structure of limestone caused by the re-crystallisation of calcite
• METAMORPHIC ROCKS ARE RESISTANT TO EROSION