coastal environments Flashcards
what is weathering
the gradual breakdown of rock, in situ. It can be divided into 3 different types: mechanical, chemical and biological
Give an example of each type of weathering
Mechanical: freeze-thaw
Chemical:oxidation
Biological: plant roots
Four erosional processes:
hydraulic action, solution, abrasion, attrition
what is hydraulic action
the power of the waves forces water into cracks in a cliff. this compresses the air in the cracks. when the wave retreats the compressed air blasts out forcing the rock apart and crack to widen.
what is attrition
material carried by waves collide together causing them to become smaller and rounder over time.
what is abrasion
the waves pick up sand and pebbles and hurl them at the cliff face, wearing the cliff away. also applies to sediment in rivers wearing banks away.
how are headlands and bays formed
Formed from alternating bands of harder and softer rock. Less resistant rock is eroded faster, and more resistant is eroded less by the erosional processes, leaving headlands on either side of a bay.
what is longshore drift
the zigzag movement of sediment along the coast, travelling diagonally onto the beach by swash and dragged back at right angles by backwash.
what is sliding
an increase in water (e.g after heavy rain) reduces friction and increases weight causes material to become unstable and rapidly move downhill.
what is slumping
whole segments of the cliff moving down, causing rotational scars (land is bumpy like stairs)
how’s a spit formed
sediment carried by longshore drift is deposited where coast suddenly changes direction so the water is shallow and protected by the headland and spit slowly builds up
how does vegetation protect the coast
it stabilises loose material and reduces erosion
three examples of vegetation/structures that protect coast
sand dunes, mangroves and salt marshes
formation of caves, arches, stacks and stumps
crack in cliff opens up and grows due to erosional processes. Cave becomes larger until it breaks through headland, forming an arch. Arch is eroded and forms a stack which is eroded further to a stump.
where are sand dunes found
Further from the shore in areas where there’s lots of sand and high winds
where are salt marshes found
mid-level mudflats that lie high above the high water mark.
where are mangrove forests found
found in over 100 countries in subtropical and tropical climates
Abiotic characteristics of the Great Barrier Reef
Developed in shallow tropical waters, on a very shallow continental shelf.
Beyond this is a steep 2,000m drop off
Average depth of just 35m
900 islands
Biotic characteristics of the Great Barrier Reef
Largest living structure on the planet
3,000 individual coral reef
over 450 species of hard coral
symbiotic relationship between microscopic algae and coral
symbiosis between clownfish and anemones
Threats to coral reefs
Development - increased tourism means more human activity in water, more fishing, pollution from development
Industrialisation - ports developed, lots of pollution, more fishing
Agriculture - deforested land accelerates soil erosion, pollutes the sea.
Invasive species - e.g. crown of thorn starfish
climate change - coral bleaching
what is coral bleaching
When the temp of the water increases due to global warming, the small plants inside polyps can’t photosynthesise as effectively, so they are gotten rid of. Coral has lost its most important food source and starves. Flesh becomes clear and the white we see is the bones.
name some stakeholders of the coast
- wildlife lovers
- fishermen
- divers
- tourists
what are the 4 shoreline management plans
do nothing
managed retreat
hold the line
advance the line
hard engineering definition and examples
building and using man-made, artificial structures to protect coastlines. Often expensive, short-term and unsustainable. Examples: groynes, gabions, rip rap, sea walls, revetments
