Geog 1 - Coastal Environments - Key

Question 1

Abandon line

Answer 1

The strategic withdrawal of human occupation in areas of high risk. Use of less expensive and sustainable methods to “abandon the line” of the coast, often unpopular with farmers and property owners. E.g. National Trust policy Studland Bay.

Question 2

Abrasion

Answer 2

The wearing away of shoreline by sediment carried by waves. Also erosion by friction scraping, scouring and rubbing of load in contact with banks and bed (Corrasion)

Question 3

Accretion

Answer 3

The accumulation of marine sediments. Where deposition exceeds erosion.

Question 4

Advance line

Answer 4

This involves active intervention to produce a defence line that is seaward in some way of the existing line. This would usually involve some form of reclamation, the construction of offshore breakwaters or similar.

Question 5

Arch

Answer 5

A raised are left when two caves erode back to back on a headland. E.G. Durdle door.

Question 6

Attrition

Answer 6

The reduction and rounding of particles of sediment carried in water repeated collision with each other and the shore.

Question 7

Backwash

Answer 7

Movement of water back towards the sea after a wave has broken.

Question 8

Bar

Answer 8

Coarse grained deposit of sediment extending across the mouth of a bay, sometimes reaching the other side and sealing off the entrance E.g. Looe Bar.

Question 9

Benefit cost ratio

Answer 9

The ratio of the present value of benefit to the present value of costs. Benefits and costs are compared with the “without project” case for each option

Question 10

Berm

Answer 10

Low hill of sand or gravel that forms at the upper limit of the swash. They are short-term features and are removed by successive tides and storms.

Question 11

Beach nourishment

Answer 11

Sand and shingle brought from elsewhere are added to beaches to maintain their breadth and depth to protect from erosion in a natural way E.G. Hengistbury Head.

Question 12

Blow - hole

Answer 12

A chimney or pipe leading from a cave up through a cliff to the surface. Caused by erosion and often exploitation of joints in the geology.

Question 13

Breaching

Answer 13

Failure of defences allowing flooding by tidal or storm action.

Question 14

Char

Answer 14

An island formed from silt deposition in a delta. The land is about at sea level. It is very fertile and attracts settlers desperate for land. However can be easily washed away by monsoon floods and cyclones. Salt water reduces their fertility.

Question 15

Constructive waves

Answer 15

Low frequency 6 - 8 per minute which have elliptical water motion, with powerful swash and weak backwash. They build up deposition.

Question 16

Concordant geology

Answer 16

The alignment of geological outcrops which are parallel to the coastline. E.G. Dorset coast at Lulworth.

Question 17

Corasion

Answer 17

Erosion by friction of load in contact with banks and bed (abrasion)

Question 18

Corrosion

Answer 18

Includes the dissolving of carbonate rocks (limestone) in sea water and the evaporation of salt crystals which expand on formation and help the rock to disintegrate.

Question 19

Cusp

Answer 19

Crescent - shaped embayments developed on beaches of mixed sediments.

Question 20

Cuspate foreland

Answer 20

Is a triangular accumulation of sand an or gravel located alone the coastline. This feature is formed by longshore drift from opposing directions E.G. Dungeness

Question 21

Defence line

Answer 21

The crest of a sea wall / revetment (man made defences) or the crest of dunes or the cliff edge (natural defences)

Question 22

Deltas

Answer 22

Form when the amount of sediment delivered at the mouth of a river exceeds the amount removed by waves and tidal currents.

Question 23

Destructive waves

Answer 23

High frequency 13 - 15 per minute waves which have circular water motion, with weak swash and powerful backwash. They erode.

Question 24

Differential erosion

Answer 24

Varying rates of erosion relating to geology and energy of coastline. Resistant coastlines have hard rocks massive structure consolidated and not susceptible chemical weathering E.G. Land end (granite)

Question 25

Discordant erosion

Answer 25

Coasts which cut across the rock structure. E.G. Dorset North of Swanage Bay.

Question 26

Diurnal range

Answer 26

The difference between the lowest temperature and the highest temperature in a 24 hour period.

Question 27

Do nothing

Answer 27

Where no action is taken to protect the coastline

Question 28

Downdrift

Answer 28

In the direction of the net longshore transport of beach material

Question 29

Dunes

Answer 29

Concentration of mound like landformes composed of sand that has been blown off the beach by onshore wind. Embryo dunes first, followed by foredunes (yellow) grey dunes, then wasting dunes.

Question 30

Eustatic

Answer 30

Changes in sea level by variation in the amount of water in the oceans.

Question 31

Fetch

Answer 31

The distance of uninterrupted water surface over which the wind has blown to form waves. Longer fetch means higher energy waves.

Question 32

Fiord

Answer 32

Very deep U-shaped estuaries formed by the drowning of glaciated valleys on the Western side of land masses in temperate latitudes. E.g. Drygalski Fiord, South Georgia

Question 33

Flocculation

Answer 33

River load particles join together on contact with the salt in the sea water, increasing their weight and causing them to drop / be deposited.

Question 34

Flood

Answer 34

A temporary excess of water that spills over onto land

Question 35

Frequency

Answer 35

How often floods occur

Question 36

Gabion

Answer 36

Cages enclosing rocks to defend the coast.