Coastal geomorphology

Question 1

importance of coasts

Answer 1

• population pressures: 3 billion live on coastal zone
• Impact of coastal disasters and storm surges
• sea level rise/coastal erosion: isostatic change/climate change

Question 2

coast

Answer 2

area between land and sea

- extends inland until meets a different geographical setting

Question 3

shoreline

Answer 3

precise boundary where water meets adjacent dry land

• not clearly defined
• salt marsh system for land or sea

Question 4

coastal influences

Answer 4

• wind dominated
• tide dominated
• river dominated

Question 5

coastal zones

Answer 5

• backshore
• foreshore (swash zone)
• inshore (surf and breaker zone)
• offshore

Question 6

tidal currents

Answer 6

• driven by gravitational attraction of sun and moon

- amplified by the configuration of the coastline

Question 7

wave energy

Answer 7

• dictated by wind strength

- may reflect distance over which wave energy has travelled (fetch)

Question 8

river dominated system

Answer 8

• where wave/tide energy is low
• where major river system deposit large amounts of sediment
• deposition from river system may dominate coastal process

Question 9

tides

Answer 9

daily fluctuations in the height of the ocean, caused by gravitational attraction of water to moon and sun

• tidal range varies depending on latitude and the shape of the coasts
• cause water level changes at the coast

Question 10

waves

Answer 10

• transport energy by motion, ultimate sources of wave energy are the sun and winds
• energy and size dependent on wind speed, duration and distance travelled (fetch)
• turbulent airflow = pressure variation = wave formation = disturb airflow = sustain waves

Question 11

Longshore current

Answer 11

current that parallels shoreline developed by waves coming in at an angle to shore

Question 12

Types of tides

Answer 12

• diurnal & mixed semi-diurnal
• semi-diurnal tides most places
• spring tides higher than normal tides
• neap tides lower than normal

Question 13

Tidal ranges

Answer 13

• micro tidal <2m
• meso tidal 2-4m
• macro tidal >4m
  tidal range has greater impact than type of geomorphology

Question 14

tide types

Answer 14

• flood tide, incoming
• ebb tide, outgoing
• maximum tidal velocity is achieved at the tide midpoints (most geomorphological work is done)

Question 15

Wave types

Answer 15

• spilling: low angle shore, foamy
• plunging: moderate subsurface, or significant changes in depth
• collapsing: steep angle shore, bottom face steepens until collapse, foamy
• surging: long period waves don’t break, typical of tsunami events

Question 16

constructive waves

Answer 16

• strong swash and weak backwash

- deposition greater than erosion

Question 17

destructive waves

Answer 17

• weak swash and strong backwash

- erosion is greater than deposition

Question 18

coastal erosion

Answer 18

• waves are dominant mechanism in coastal erosion, water forced into cracks in rock at high pressures (Cavitation)
• wave energy focused on headlands: prominent cliffs that jut out into deep water
• attacks the sides of headlands & form sea caves, sea arches and sea stack by undercutting

Question 19

attrition

Answer 19

materials carried by the waves bump into each other and so are smoothed and broken down into smaller particles

Question 20

hydraulic action

Answer 20

the process involves the force of water against coast. the waves enter cracks in the coastline and compress the air within the crack. when the wave retreats, the air in the crack expands quickly, causing a minor explosion. the process is repeated continuously

Question 21

corrosion

Answer 21

this is the chemical action of sea water. the acids in the salt water slowly dissolve rocks on the coast. limestone and chalk are particularly prone to this process

Question 22

abrasion/corrasion

Answer 22

this is the process by which the coast is worn down by material carried by the waves. waves throw these particles against the rock, sometimes at high velocity

Question 23

wave cup platform

Answer 23

• waves attack the base of the cliff through the process of abrasion, corrosion, hydraulic action and attrition
• over time the cliff will be undercut and a wave cut notch is formed
• eventually the cliff becomes unstable and collapses. further cliff retreat will form a wave cut platform

Question 24

caves, arches, stacks and stumps

Answer 24

Durdle Door, Dorset

Old Man of How, orkney

Question 25

preventing coastal erosion

Answer 25

- can establish sand dunes and stabilise existing dunes | - can build seawalls: concrete or riprap structures designed to protect shoreline from waves

Question 26

coastal management

Answer 26

- no active intervention: nothing is lost if coast erodes - managed realignment: communities relocated and ban places on re-development - accommodation (communities adapt and accept risk) - hold the line (hard/soft engineering measures)

Question 27

coastal deposition

Answer 27

- occurs when amount of sediment exceeds wave/current ability to transport it - human activities often induce coastal deposition on purpose or by accident: - use groins or breakwaters to disrupt longshore current or block waves and induce deposition

Question 28

beaches

Answer 28

relatively narrow strips of sand, pebble or cobbles deposited along a shoreline - 90% of beach sediment comes from streams that drain to coast, transported by longshore currents

Question 29

spit and/or hook

Answer 29

narrow strip of sand that grows across the moth of bay due to longshore current

Question 30

barrier islands

Answer 30

long narrow island made of sand that flank main shoreline and separate bays from open ocean - needs abundant coastal sediment and low coastal relief (little or no recent coastal uplift)

Question 31

tombolo

Answer 31

narrow strip of sediment deposited behind a sea stack by refracted waves

Question 32

estuary head

Answer 32

where the river enters

Question 33

estuary margins

Answer 33

the sides

Question 34

an estuary mouth

Answer 34

opening to the sea

Question 35

delta development

Answer 35

over time islands of sediment appear in a triangle shape in an estuary

Question 36

salt marsh development

Answer 36

- intertidal areas of fine sediment transported by water and stabilised by vegetation 4 elements needed for development: - a stable area of sediment covered by the tide for a short time - a supply of sediment - low water velocities - a supple of seeds for the establishment of vegetation cover

Question 37

Primary coast

Answer 37

shaped by non-marine processes (glaciations, streams etc.) | - often a landscape drowned by rising sea level

Question 38

secondary coast

Answer 38

shaped by coastal erosion and deposition features outline previously - primary coasts often have secondary features

Question 39

plate tectonics

Answer 39

rifted continental margins tend to be dominated by deopositional features - active margins tend to be dominated by erosional features

Question 40

summary of coastal features

Answer 40

coastal forms correlate strongly with energy of the processes operating, much depend on: - geology, topography, Relief & climate - highly dynamic environment, ever changing - future sea-level rise will enhance and accelerate the effectiveness of erosion processes