Rates of erosion and coastal succession

Question 1

Coastal recession

Answer 1

How fast a coastline is moving inland.

Question 2

What influences the rate of coastal recession?

Answer 2

Lithology and rock type

Question 3

What are the 3 major rock types?

Answer 3

Igneous, Sedimentary, Metamorphic

Question 4

rock types sedimentary igneous metamorphic in order of resistance

Answer 4

most resistant

• igneous
• metamorphic
• sedimentary

Question 5

Example of igneous rock

Answer 5

• Granite
• Basalt
• Dolerite

Question 6

Erosion rate of igneous rock

Answer 6

Very slow, less than 0.1cm per year. Rocks are crystalline, with interlocking crystals, makes strong, hard, erosion resistant rock. They have few joints, therefore few weaknesses for erosion to exploit.

Question 7

Erosion rate of metamorphic rock

Answer 7

Slow, 0.1-0.3cm per year. Crystalline metamorphic rock is resistant to erosion. Foliation - crystals are orientated in one direction, which produces weaknesses. Often folded and heavily fractured, forming weaknesses which erosion can exploit.

Question 8

Examples of metamorphic rock

Answer 8

• Slate
• Schist
• Marble

Question 9

Examples of sedimentary rock

Answer 9

• sandstone
• limestone
• shale

Question 10

Erosion rate of sedimentary rock

Answer 10

Moderate to fast erosion rate. 0.5-1cm per year. Clastic rocks are eroded faster. Age is important, with geologically young rocks being weaker. Many bedding planes and fractures, like shale, vulnerable to erosion.

Question 11

Clastic rock

Answer 11

rocks consisting of sediment particles cemented together

Question 12

Crystalline rock

Answer 12

rocks made up of interlocking crystals

Question 13

Unconsolidated material

Answer 13

Sediment which has not been cemented to form a solid rock, process called lithification.

Question 14

How does unconsolidated material influence rates of recession?

Answer 14

When rock forming cliffs is unconsolidated material, rates of recession are much greater.

Question 15

What is erosion and weathering resistance influenced by?

Answer 15

• how reactive minerals in the rock are when exposed to chemical weathering
• whether rocks are clastic or crystallines, crystalline are more erosion resistant
• the degree to which rocks have cracks, fractures and fissures, which are weaknesses exploited by erosion.

Question 16

Example of fast receding coastline due to unconsolidated sediment

Answer 16

Boulder clay Holderness Coast, 2-10m per year.

Question 17

Why do cliff coastlines have complex cliff profiles?

Answer 17

• Because they’re made of different rock types, which have different rates of erosion due to the alternating types of strata.
• permeability also influences cliff profiles.

Question 18

How does permeability influence cliff profiles?

Answer 18

Permeable rocks allow water to flow through them, e.g. sandstone and limestone. Impermeable rocks do not allow this to happen, like clays and most igneous and metamorphic rocks. Permeable rock, water flows between layers, removes cement that holds sediment together, weakens rock. Causes high pore water pressure. Water from below ground onto rock, causes surface runoff erosion.

Question 19

Pore water pressure

Answer 19

Internal force within rocks, exerted by the mass of groundwater within permeable rocks.

Question 20

How does coastal vegetation protect coastlines from erosion?

Answer 20

Plants have a stabilising influence on coastlines

Question 21

How does vegetation stabilise coastal sediment?

Answer 21

• roots bind sediment particles together, making them hard to erode
• when submerged, plants provide a protective layer, so sediment surface is not directly exposed to moving water and erosion
• plants protect sediment from erosion from wind by reducing wind speed at the surface because of friction with the vegetation.

Question 22

why do coastal plants need to be specially adapted?

Answer 22

because the combination of salt water, strong winds, tides and waves makes the coast an extreme environment

Question 23

what are the two types of specially eroded coastal plants?

Answer 23

Halophytes and xerophytes.

Question 24

Halophytes

Answer 24

salt tolerant plants

Question 25

Xerophytes

Answer 25

drought tolerant plants

Question 26

Plant succession

Answer 26

The changing structure of a plant community over time as an area of initially bare sediment is colonised.

Question 27

basic process of plant succession on a coast with a supply of sediment and deposition takes place.

Answer 27

Pioneer plant species grows in bare sand/mud. Forms first stage of plant succession. Each step in plant succession is a seral stage. The end result is a climax community

Question 28

Examples of coastal climax communities

Answer 28

Sand dunes and salt marshes

Question 29

How does succession begin at coastal dunes?

Answer 29

Succession begins by the colonisation of embryo dunes by a pioneer species.

Question 30

How to embryo dune pioneer plants contribute to succession?

Answer 30

• stabilise mobile sand by root systems
• reduce wind speed at the sand surface, allowing more sand to be deposited.
• add dead organic matter to sand, begins soil formation

Question 31

How do embryo dunes lead to further colonisation?

Answer 31

Embryo dunes alter the environment from harsh, salty. mobile sand to an environment that other plants can tolerate. New plant species colonise embryo dunes, creating a fore dune.

Question 32

How does succession occur at bare mud in estuaries

Answer 32

• Estuaries are sheltered from strong waves, sediment can be deposited.
• Rivers transport a supply of sediment to the river mouth, which may be added to by sediment flowing into the estuary at high tide.
• Forms a salt marsh.

Question 33

what does sand dune succession rely on?

Answer 33

Specialised plants, marram grass is an example. Tough, long, flexible waxy leaves can cope with being sand blasted in strong winds, and are designed to limit water loss through transpiration.

Question 34

How are sand dunes a dynamic environment?

Answer 34

• Periods of wind create low areas within sand dunes called dune slacks, erosion stops when damp sand at the water table is exposed as this cannot be easily eroded.
• embryo and fore dunes are prone to wind and wave erosion, especially during major storms, but as long as the supply of sediment to the coast resumes, new embryo dunes will form and the dune front will stabilise.