GCSE Coastal Zone Flashcards
What factors shape our coastline
Waves
Rock type
Land processes
Marine Processes
What are the land processes shaping the coastline
Weathering
Mass movement
What are the marine processes shaping the coastline
Transportation
Deposition
Erosion
What is the fetch
The distance the wind has blown
What depends on the fetch
Size and strength of wave
Larger wave means
Greater fetch, stronger wind
Waves strongest from
South West Britain
Why do waves break
Waves slow at beaches because of FRICTION between wave and beach– causes it to break
Define swash
Forward movement of a wave UP a beach
Define backwash
Movement of a wave back DOWN a beach after the wave broken
Swash/Backwash transfer of energy
Transfers energy UP/DOWN a beach
Types of waves
Constructive, destructive
Characteristics of constructive
- builds beaches
- low waves
- carries material up the beach
- most common in summer
- material deposited when backwash soaks into sand/slowly drains away
Characteristics of destructive
- destroys beaches
- high and frequent waves
- strong backwash pulls material out to sea
- most common in winter
What affects height and shape of coastal scenery
Resistance, permeability, structure of rock
What is resistance
Rocks can be hard (granite) and soft (clay)
What is permeability
Rocks can be porous (chalk), permeable (limestone) and impermeable (granite)
What is structure
Rocks can have interlocking crystals, joints, faults and bedding planes
Weathering and mass movement are…
SUB-AERIAL PROCESSES/land processes
Define mass movement
Downhill shifting of rocks and loose material under the influence of GRAVITY which is greater than the force supporting it
What is slumping
Common when cliffs are of clay. During heavy rainfall- becomes saturated+heavy and oozes towards sea as part of a MUD or DEBRIS flow
(mudflow, rotational slip)
What is sliding
When large chunks of rock slide downslope quickly without warning
(landslide, rockfall)
Rotational slip
Rotational movement on a concave slide plane. Weak rock (clay)/soil becomes saturated- in response to GRAVITY simply collapses
Mudflow
Weak rock (clay, volcanic ash)/soil becomes saturated and FLOWS downhill. Can be slow/rapid. If mixed with melted snow/ice/ash from volcanoes– become lahars (deadly)
Rockfall
On steepest slopes. Rock fragments/slabs suddenly detach and angular debris falls to base as TALUS/SCREE. Gradual processes- freeze thaw weathering OR sudden and dramatic- earthquakes
Landslide
Flat/planar side plane with impermeable bedding plane is lubricated after rainfall- making slope slippery and landslides RAPID and deadly.
Landslide
Flat/planar side plane with impermeable bedding plane is lubricated after rainfall- making slope slippery and landslides RAPID and deadly.
Define weathering
The breakdown or decay or rocks in their original place (in SITU) or close to the earths surface, mainly caused by weather conditions (change in temp+rainfall e.g.)
Factors affecting weathering rate
Climate, vegetation, animals colonising cliffs
Erosion-not in situ- caused by
Movement of water, ice and wind
Types of weathering
Biological, chemical, mechanical
Biological weathering (all)
PLANTS- tree roots grow into cracks and widen them
ANIMALS- burrow into weak rocks and force apart
What is Chemical weathering
Breakdown by changing its chemical composition and causing rot and decay. Warm and wet climates
Carbonation, solution
What is Mechanical weathering
Breakdown of rock w/out changing chemical composition. Common where rock is bare/unprotected from extreme climates.
Exfoliation, freeze thaw
Carbonation
Rainwater has some CO2 in it making it a weak carbonic acid. It reacts and dissolves rocks e.g. limestone with CACO3. Removed using running water. Forms distinctive landforms
Solution
Minerals (eg rock salt) and rocks DISSOLVE in rainwater
Exfoliation
Warm climates-
In warm day, rock heats and EXPANDS. In cool night rock cools and CONTRACTS. Repeats, wears rock and it peels like an onion
Freezethaw
Happens where temp alternates above/below 0C
Rainwater in cracks+joints freezes subzero. Expands by 9%, puts PRESSURE on rock. FORCES cracks to widen. Ice thaws and melts and contracts above 0C, PRESSURE RELEASED. Repeat, causes rock to break apart and form scree
Define coastal erosion
Wearing away of the land by the action of waves. When a wave smashes down on a beach/against a cliff- it carries out erosion.
(hydraulic action, abrasion, corrasion, attrition, solution)
Hydraulic action
Sheer power of waves. Waves smash against a cliff- trapped air is compressed and blasted through cracks+holes causing rock to fall apart. Cavitation is the explosive force of trapped air in a cliff
Abrasion
Sandpapering effect causing rocks to smoothen and become smaller after dragged, scraped and rubbed along a rocky surface
Corrasion
Sea throws fragments of rock against a cliff face, causing it to scrape+gouge the rock
Attrition
Rock fragments in the sea bash against each other so become more rounded and smaller as they break into smaller fragments
Solution
Small, weak and vulnerable rocks e.g. limestone and chalk dissolve in seawater
Methods of transportation
LSD, traction, saltation, suspension, solution
Traction
Large heavy rocks ROLLED along the seabed by FORCE of the seawater
Saltation
Small rocks and pebbles and sand grains BOUNCE along the seabed by FORCE of seawater
Suspension
Small material (e.g. sand, silt) is CARRIED within the water
Solution
Small, weak and vulnerable soluble rocks are dissolved and are carried along within the water
What is Longshore drift
Movement of material along a coast in a zig zag formation
Process of LSD
Wave approaches in OBLIQUE angle, following direction of prevailing wind. Swash carries material up the beach after wave has broken. Backwash returns material at a right angle down the beach (shortest route under gravity’s influence). Material ZIGZAGS over time across beach.
What are the features of erosion?
Headland and bays
Cliffs and wave-cut platforms
Caves, arches and stacks
Where do headlands and bays form?
Discordant coastline- alternating rock types/ erosion resistance is different
Define concordant coastline
Coastline with the same type of rock along its length
Define headland
A promontory of land jutting out into the sea
Define bay
A broad COASTAL INLET often with a beach
Formation of Headlands and bays
Cliffs rarely erode at an easy pace.
Some types of more rock are more resistant to erosion
At discordant coastlines, destructive waves erode the softer rock quicker to form bays and coves (clay)
Waves cannot wear away resistant rock as easily so harder rock sticks out as HEADLANDS (sandstone, limestone, chalk)
Define a wave-cut platform
A wide, gently sloping rocky surface at the foot of a cliff
Define a wave-cut notch
A small indentation cut into a cliff by coastal erosion roughly at the level of high tide
How are wave-cut platforms formed?
Waves cause most erosion at the foot of a cliff
Concentrated marine erosion causes the waves to undercut the foot of the cliff when wave energy is at its max
Erosion continues and the notch enlarges and widens until the unsupported cliff collapses. This is aided by gravity and SA processes.
Repeated collapsing causes cliff to retreat, increase in height and leave a rocky platform behind.
How are caves, arches and stacks formed.
- lines of weaknesses eg faults, cracks occur in headlands (esp vulnerable rock, chalk, limestone)
- Corrasion, hydraulic action erode, widen fault–cave
- Cave widened, deepened. Sometimes there’s back to back cave
- Sea cuts through– arch
- Marine erosion–notches at base of arch
- SA processes weaken top+gravity helps towards collapse
- Isolated stack attacked by marine processes and gravity
- notches form + are undercut– stump
- headland retreats, process repeats
