COASTS THEORY Flashcards
What is freeze-thaw? (Mechanical weathering)
Water enters crack in rocks, water freezes overnight + expands by approx. 10% in volume. Increase in pressure causing more cracks to develop. Process is repeated and cracks grow, wakening cliff.
What is salt crystallisation? (Mechanical weathering)
Seawater evaporates, salt left behind. Salt crystals grow over time, exerting pressure on rock, forcing cracks to widen.
What is carbonation? (Chemical weathering)
Rainwater absorbs CO2 from air to create weak carbonic acid. Reacts with calcium carbonate in rocks to form calcium bicarbonate which can then be easily dissolved. Acid rain reacts with limestone to form calcium bicarbonate which is then easily dissolved allowing erosion.
What is oxidation? (Chemical weathering)
Minerals exposed to air through cracks + fissures, mineral becomes oxidised increasing its volume, causing rock to crumble
What is solution? (Chemical weathering)
Rock minerals such as rock salt are dissolved
What is mass movement?
Movement of material down a slope under influence of gravity
What are the different types of mass movement?
creeps, flows, slides and falls
What is soil creep (mass movement)?
Slowest but most continuous form of mass movement involving movement of soil particles downhill. Particles rise + fall due to wetting + freezing, causing soil to move down slope. Leads to formation of shallow terracettes.
What is solifluction (mass movement)?
Occurs mainly in periglacial environments where land is frozen. Top layers thaw during summer (but lower layers stay frozen due to permafrost) surface layers flow over frozen layer.
What are mudflows (mass movement)?
Increase in water content of soil = reduction in friction, leading to earth and mud to flow over underlying bedrock. Water can get trapped w/in rock increasing pore water pressure, forcing rock particles apart + weakening slope.
What is rock fall (mass movement)?
Occurs on sloped cliffs when exposed to mechanical weathering. Leads to scree (rock fragments) building up at base of slope.
What are landslides (mass movement)?
Heavy rainfall leads to water between joints + bedding planes which can reduce friction and lead to landslide. Occurs when block of intact rock moves down cliff face v quickly along flat slope.
What are slumps (mass movement)?
Slope is curved, thus occur in weak + unconsolidated clay + sand areas. Build up in pore water pressure leads to land to collapse under own weight. Can create scarred/terraced appearance to cliff face.
What is runoff (mass movement)?
when heavy rain washes material from the surface of a cliff over the edge and down onto the shore.
What causes waves?
Wind blows over the surface of the sea. As wind drags over water surface, friction causes disturbance and waves form
What movement do waves follow?
Waves follow an orbital movement
What controls wave energy?
force of wind + its direction, duration of wind, fetch - the longer the fetch, the more energy wave has
what are the three types of breaking wave?
spilling - waves break on to gently sloping beaches, water flows gently forward as waves breaks
plunging - steep waves breaking on to steep beaches ; water falls vertically downwards
surging - low-angle waves breaking on to steep beaches; wave slides forward
constructive waves features:
- build beaches
- are product of distant weather systems
- have longer wavelengths , lower height + are less frequent
- swash is bigger than backwash so add to beach materials
destructive waves features:
- have shorter wavelength, greater height + are more frequent
- backwash is greater than swash so sediment dragged offshore
- create steeper beach profile, though over time will flatten beach as material is drawn backwards
How are tides created?
tides are produced by gravitational pull of moon + sun - as moon orbits Earth, high tides follow it
When do the highest tides occur?
when the moon + sun are aligned, when gravitational pull is at its strongest
What is tidal range?
Difference between water level at high tide + low tide
When are tidal ranges low?
Are low in enclosed seas - wave action is restricted to narrow area of land
When are tidal ranges high?
Are higher in places where coast is funnelled, eg estuaries
What is lithology?
Physical + chemical composition of rocks
Is carboniferous limestone permeable or impermeable?
Carboniferous limestone is permeable bc of many joints
What makes a rock have a strong lithology?
Rocks (eg basalt, granite) made of dense interlocking crystals + are v resistant to erosion
What are the various sediment sources?
Rivers, sea bed, erosion of coastline, transported material, human activity (beach nourishment)
What is scree?
Collections of loose rock at base of slope
What is regolith?
Collective name for all of material produced by weathering
What is abrasion (corrasion)?
material carried by waves used as ammunition to wear away rocks on cliff or wave-cut platform - material is thrown or rubbed against it repeatedly
What is suspension?
Form of transporation - process by which very small particles held in water
What is traction?
Form of transportation - large stones + pebbles rolled along sea bed + across beach