coasts- weathering and geology
Terms in this set (66)
what are geomorphological processes?
natural process acting on and shaping the land
what are marine processes?
processes that operate on the coastline connected with the sea
what are sub-aerial processes?
processes of the air and weather around that decompose and disintergrate the rocks on the coast by weathering
mechanical (physical) weathering
the physical breakdown of rocks into smaller fragments such as expansion and contraction due to temperature change
freeze thaw/frost shattering
when temperatures fluctuate either side of 0 degrees - the water in cracks freeze which then expands by 9% - creates pressure within a joint causing bits to break off
where is freeze thaw common?
coastal Artic areas such as Norway,Iceland and Alaska
when a rock becomes saturated with water containing salt and pressure is exerted on the rock due to the enlargement of salt crystals in comparison to the spaces they are formed in
where is salt weathering found?
in softer rocks such as chalk and when it is warm enough for the water to be evaporated away during low tide
the decay of decomposition rock in situ
where does chemical weathering take place?
in the presence of water which acts like a dilute acid
where carbon dioxide dissolves in water making a weak, carbonic acid which acts on limestones
when does carbonation increase?
with decreasing temperatures
why does carbonation decrease in lower temperatures?
as CO2 is more soluble at lower temperatures
the breakdown of rocks by the action of vegetation and coastal organisms
the piddick can drill into solid rocks especially chalk and produce a sponge like rock and seaweed can prise away loose rocks.
dissolved organic material in the form of stable organic acids
where are humic acids very significant?
in limestone areas e.g. the Karst Towers in Thailand
common on coastlines that are steep
what is mass movement dependent on?
level of cohesion within sediment, the height of the slope and the slope's angle, grain size within sediment + temperature and level of saturation
where softer material overlies much more resistant materials
occurs from cliffs undercut by the sea or on cliffs affected by mechanical weathering
a process that assists mass movement and may take the form of a stream emerging in a bay
a block of rock that moves rapidly downhill along a planar surface
what are landslides triggered by?
earthquakes or very heavy rainfall when the slip surface becomes lubricated + friction is reduced
the sudden collapse or breaking away of individual rock fragments at a cliff face
what are rockfalls associated with?
steep or vertical cliffs in heavily jointed and resistant rock
what is rockfall triggered by?
what happens once rocks break away from their source?
rocks fall/bounce down the slope to form scree and scree often forms a temporary store
rotational cliff slumping
commonly occur in weak and unconsolidated clays and sands
permeable rock overlies impermeable rock =
a build up of pore water pressure
what is rotational cliff slumping characterised by?
by a sharp break or slope
what can multiple rotational cliff slumps result in?
a terraced appearance on the cliff face
the impact of water and its shock-wave pressure on the rock surface
what impact does hydraulic action have on coastal engineering?
sea walls need to be replaced every 25-30 years
breaking wave traps air as it hits a cliff face and the force of water compresses this air into any gap in the rock face creating pressure in joint or fissure. As water pulls back there is an explosive effect of the air under pressure being released.
material of the sea is picked up from sand to large rocks and hurled against the cliff face
form of carbonation and technically weathering
when loose rocks are broken down into smaller and more rounded pebbles
the rolling of sediment along the sea bed and occurs in high energy environments
when sand and silt is carried along by moving water
when the energy of moving water decreases and is no longer competent to continue entraining sediment so it will deposit it
wind transports sediment near the surface by saltation.
transportation of sediment through a series of leaps or bounces
where is sand deposited during the process of aeolian transportation?
the rear of the beach beyond tidal range in which forms sand dunes
wave cut notch
where the waves undercut the foot of the cliff
wave cut platforms are exposed at?
where are wave cut platforms covered?
the notch enlarges until?
the cliff collapses above
the cliff will increase in?
wave cut platform
the slightly sloped foot at base of sea cliff
why are clay cliffs disadvantaged?
as rain makes the clay very slippery
what will rain eventually do to the clay cliff?
huge blocks of clay will slide past each other down the slope
bodies of water surrounded on three sides by land
points of high land that stick out into a body of water
where do bays form?
along coastlines where there are alternating outcrops of harder and softer rock
what do destructive waves erode?
areas of softer rock to form bays
what can waves not wear away?
what do headlands protect?
adjacent bays from destructive waves
develop when groundwater dissolves limestone
a natural rock formation due to the erosion by sub-aerial processes
a steep and vertical column or columns of rock in the sea by the coast
a crystalline rock by the cooling and solidification of magma such as granite
a rock made up of sediments deposited in distinct layers such as limestone
a rock that has been altered by pressure and heat e.g. slate
the overlying weight of sediment over time causing compaction, cementation and hardening
generally younger rocks that are loose and can be easily eroded