Coastal Landscape Development (workbook 3a)

Different Landforms

Created by erosion

Created by deposition

Created by sea level change

stump

stack

bay

headland

arch

wave-cut platform

wave-cut notch

cave

shingle beach

sand beach

spit

bar

tombolo

offshore bar

mudflat

saltmarsh

sandunes

cuspate foreland

longshore drift and deposition are fast- minute by minute

erosion and weathering are slow- years

Timescales for formation

INSTANTANEOUS- affected by changes that operate within a single cycle (e.g waves or tides). Ranges from seconds to weeks e.g beach

EVENT- time span from an individual event through to seasonal variations. varies from a few days to many years e.g a sand dune

ENGINEERING- fluctuations take place over longer periods of time. from years to decades to centuries e.g stack

GEOLOGICAL- from decades to millenia as changes take place in sea level and climate e.g spit

raised beach

marine platform

Fjord

Dalmation Coast

Rias

OREGON COAST- made up of many distinctive landforms formed by erosion and deposition over varying time periods

GEOLOGY- significant factor in change at the coast as it can determine the speed of erosion and the supply of sediment

other factors include prevailing winds, fetch, wave type, tides, wind and the moon

Sea level change

the last ice age ended around 11,500 years ago and we are now in a period known as the holocene

Transgression- rising sea levels- coastline retreating

Regression- sea levels fall as ice is trapped in glaciers and ice sheets

coastal landscapes

OLD HARRY- stack- shows how a landscape changes over time

KIMMERIDGE, DORSET- wave cut platform, headland and a cliff

ETRETAT, NORMANDY, FRANCE- bay, headland, cliff, stack, arch

DOVER, KENT- cliff, wave cut platform

SANTA CRUZ ISLAND, CALIFORNIA- cave

BAJA CALIFORNIA, MEXICO- arch, stack

ALGARVE COAST, PORTUGAL- stack

tectonic movement where crustal plates move and land is submerged and emerged may change sea levels

formation of a stack

BLOWHOLE- vertical erosion (marine processes) exploit weaknesses in rock. Water forces itself upwards and can emerge at the surface

GEO- when rock collapses and forms a steep-sided inlet

formation of a spit

more coastal landforms

sand dunes

1) sub-aerial processes occur on top of the cliff

2) weaknesses are created by weathering e.g solution

3) erosion occurs at the cliff foot

4) creates weaknesses in the rock

5) wave-cut notch formed by erosion e.g wave pounding

stack 3

6) cave formed by further erosion e.g wave quarrying

7) arch formed by undercutting by erosion e.g hydraulic action

8) stack formed from weathering causing the arch to collapse

9) cliff recession by erosion and slumping

10) wave cut platform exposed at low tide

CAPE COD, MASSACHUSETTS- sands dunes, sand beach

CAPE HATTERAS, NORTH CAROLINA- barrier island

CHESIL BEACH, DORSET- tombolo

NEW YORK STATE- offshore bar

CHAMPAGNE BAY, VANATU- sand beach

FAREWELL SPIT, NEW ZEALAND- spit, saltmarsh

e.g Dawlish Warren, Devon

1) longshore drift carries a supply of sediment along the shore

2) where the coast changes direction, material is deposited in open sea by longshore drift

3) material accumulates over time so that it lies above the level of the water and a spit develops

4) vegetation begins to grow, helping colonise the spit

5) the end of the spit is shaped by waves from other directions so that it forms a hook

6) if sediment continues to be supplied, the spit may grow beyond the hook

TOMBOLO- a spit joining an offshore island to the mainland e.g Chesil beach or Tombollo Di Orbitello, Italy

LAGOON- the lake behind a spit

BARRIER ISLANDS- found in seas with shallow gradients, close to the shore away from deep water. Formed as a result of deposition from constructive waves. Form parallel to the shore e.g North Carolina/ Outer Herbrides Scotland

reasons for formation

  • accumulation of material transported by swash or wind blown sand
  • isolation of the shore when sea levels rise, higher storm beaches and sand dune ridges are left isolated
  • the emergence of previously submerged offshore bars as sea levels fall
  • spits being heavily built up by storm waves, then being breaches

OFFSHORE BAR- describes a spit that has formed across the bay to join two headlands. They can reduce erosion by reducing energy

processes

OVERTOPPING- shingle and water thrown landwards onto the ridge

CUT BACK- erosion of the seaward face of the shingle ridge due to wave action

CUSPATE FORELAND- a low-lying triangular area where sediment has been deposited e.g Kent

reasons for formation

  • waves from different directions create 2 converging spits
  • deposition of fluvial material
  • changes in direction of the coast

Slapton Sands

  • made of flint
  • developed 6,000 years ago due to sea level change
  • in 2004, storm waves overtopped the barrier and deposited shingle onto the road
  • road destroyed due to flooding

RUNNEL- dip in sand at right angle direction to the maximum fetch

RIDGE- collection of sediment by the shore

BERM- ridge of material running across the back of a beach, found at the highest point on a beach that a wave has reached

BEACH CUSP- crescent shaped indentation on the seawards edge of a berm, related to swash distance

STORM BEACH- material deposited from a storm found at the upper shore

Dunes of Flanders, France

example of an aoelian feature

form when:

  • large supply of sand
  • large tidal range so sand dries out
  • flat surface gradient
  • sufficient space
  • when there is a stabilising agent

wind transports grains by:

  • SALTATION- the main form of transport. sand grains are picked up by the wind then bounced along
  • SUSPENSION- lighter, smaller grains can be picked up and carried in air by the wind
  • SURFACE CREEP- traction type process where grains are rolled along by the wind

EMBRYO DUNES- take 10-20 years to develop, less high as no input of sand

VEGETATION- grows on the dunes and slows down wind speeds. Marram grass stabilises the dunes

BLOW OUT- u shaped hollow where sand in the centre has been removed

MUDFLATS/ SALTMARSH- form in low energy environments where wave action is weak. vegetation colonises mudflats to form saltmarshes. This vegetation must be tolerant of saline conditions if at coast

The Sundarbans, Bangladesh- Mangrove forests on mudflats