Coastal landscapes

Topic 3 - Coasts

littoral zone

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

• inc. subzones = offshore, nearshore, foreshore, and backshore

• reaches dynamic equilibrium

littoral zone inputs

sediment input by the action of the waves, currents and wind

littoral zone outputs

sediment washed out into the sea by erosion

high energy coast characteristics

• destructive waves

• long fetches

• high erosion - exceeds rate or deposition

• caves, arches, stacks, stumps, cliffs, wave cut platforms

low energy coast characteristics

• constructive waves

• short fetch

• higher rate of deposition - exceeds rate of erosion

• spits, bars, beaches, sand dunes, salt marches

concordant coastline

• alternating bands of hard/soft rock parallel to the coast

discordant coastline

alternating bands of rock at 90’ to the coast

• erosional landforms more common

• e.g. Dorset, greensand rock is less resistant = bay and headland creation

concordant/pacific coasts

lead to the formation of Dalmatian coasts

• offshore islands and coastal inlets parallel to the coast

• e.g. lulworth cove, Dorset = resistant limestone protects less resistant rock

discordant/atlantic coasts

• faster eroding rock retreats, leaves behind headlands

• e.g. swanage bay clays are eroded easier

bay and headland formation

• discordant coastline = retreating soft rock changes shape of coastline

• leads to wave refraction = changes way waves approach the coast

• can increase headland erosion

• leads to formation of caves, arches, stacks, stumps

coastal morphology

the shape, structure and evolution of coastal landscapes and their features

• like beaches and cliffs

what is coastal dip

the angle the rock layer forms with the horizontal bedding plane

• can dip towards land or sea

coastal dip - towards land

• steeper cliff profile

• more vulnerable to erosion processes

coastal dip - towards sea

• more gentle cliff profile

• more vulnerable to mass movement processes e.g. rockfalls

coastal lithology

the physical characteristics of particular rocks

e.g. strata, bedding planes, joints

bedding plane

natural horizontal breaks in the strata

• caused by gaps in time during periods of rock formation

joints

natural vertical cracks/fractures

• caused by contraction as sediments dry out

• or by earths movement during uplift

folds

formed by pressure during tectonic activity

• makes rocks buckle and crumple

• e.g. lulworth crumple

faults

formed when the stress a rock is subjected to exceeds its internal strength

• causes it to fracture

• faults slip/move along fault planes

land relief

the height or slope of the land

• affected by geology and geological structure

rocks with more faults and joints

more susceptible to the processes of erosion/weathering

• bc processes exert forces on weaknesses found in rock layers

igneous rock

formed from the crystallisation of magma

• contain crystals that inc. strength and reduce number of lines of weaknesses

• more resistant to erosion and weathering

• e.g. basalt and granite

• rate of erosion 0.1-0.5cm

intrusive igneous rock

formed from magma inside the earth

extrusive igneous rock

formed when magma escapes through vents on the earths surface

sedimentary rock

form from build up, compacting and hardening of sediments into layers (by lithification)

• formed in less time = susceptible to erosion and weathering

• e.g. limestone and chalk

• erode 2-6cm annually

metamorphic rock

formed from the change in structure of sed/ig rocks caused by variations in heat and pressure

• rocks are metamorphosed

• e.g. marble (by changing limestone structures)

• resistant to erosion

sand dunes

need constant supply of sand and strong wind (transports sand and obstacles to trap sand)

• from mobile dues (embryo, fore, yellow) to fixed dunes (grey dunes, dune slack)

• contain xerophytes and halophytes

xerophytes

plants that can withstand and are adapted to dry weather

• e.g. heathers = grey dunes (more humus)

halophytes

plants that can withstand and are adapted to high concentrations of salt from seawater

• e.g. sea rocket, sea crouch = on embryo dunes

• marram grass = yellow dunes

coastal system inputs

• marine - waves, storm surges

• atmospheric - water, climate change, solar energy

• land - rock type/structure, tectonics

• people - human activity, coast management

coastal system processes

• weathering

• mass movement

• erosion

• transport

• deposition

coastal system outputs

• erosional landforms

• depositional landforms

• different coast types

littoral zone sections

• back shore - above wave influence

• foreshore - intertidal/surf zone

• near shore - breaker zone

• offshore - beyond wave influence

breakpoint bar

zone of breaking waves

factors that change the littoral zone

• short term = individual wave, daily tides, seasonal storms

• long term = sea level change, climate change

unconsilated material

• loose materials

• e.g. boulder clay (holderness coast)

• not cemented together in any way and easily eroded

process of changing cliff profiles

• horizontal strata produce steep cliffs

• rocks dip towards sea, vertical joints opened by weathering

• steep dip towards sea, rock slides down cliff along bedding planes

• rocks dip inland, produce stable steep cliff

• rocks dip inland, well developed joins at 90’ to bedding planes (joints act as slide planes)

haff coasts

coasts with concordant features (spits and lagoons) parallel to the coasts

• named after haffs of the southern shore of Baltic Sea (enclosed by sand spits/dunes)