coastal landscapes and change Flashcards
(23 cards)
what is the littoral zone ?
area of the coast where land is subject to wave action.
short term factors of the littoral zone ?
tides, storm surges
long term factors of the littoral zone ?
changes in sea level and climate change
what are the four subzones of the littoral zone ?
backshore- where most of human activity occurs
foreshore- where most physical processes of erosion occur
nearshore
offshore-the open sea
why is the coast considered as an open system ?
receives inputs from outside the system, transfers outputs away from the coast.
these systems may be;
-terrestrial
-atmospheric
-oceanic
what are sediment cells
self contained streches of coastline made up of 3 components.
each cell operates as a system with inputs transfers and ouptuts of sediment
what are the three components of sediment cells ?
inputs or sources (which includes);
-cliff erosion
-river sediments
-sediment sinks
-offshore supplies
transfers (which includes);
-longshore drift
-traction/saltation/suspension/solution
-waves/currents/tides
sinks (which includes);
-spits/tombolos/offshore bars
-sand dunes
-salt marshes
-beaches
what is dynamic equilibrium ?
Dynamic as sediment is constantly being generated in the source region, transported through the transfer region and deposited in the sink region
what is a negative feedback loop ?
lessens any change which has occured within the system.
taking it away from dynamic equilibrium (positive feedback) and moving the system BACK towards equilibrium.
what is positive feedback ?
exaggerates the change, making the system more unstable and taking it away from dynamic equilibrium.
what is corrasion ?
sand and pebbles picked up by the sea from offshore sources, and hurled against the cliffs at high tide causing the cliffs to be eroded
what is abrasion ?
process where sediment is moved along the shoreline, causing it to be worn down over time
what is attrition ?
wave action cause rocks and pebbles to hit against each other, wearing each other down and so eventually becoming rounder and smaller.
what is hydraulic action ?
as a wave crashed onto a roick or cliff face , air is forced into cracks, joints and faults in the rock . the high pressure causes the cracks to force apart and widen when the wave retreats and the air expands, causing the rock to fracture over time .
what is cavitation ?
(linked with hydraulic action)
bubbles found within the water may implode under the high pressure creating tiny jets of water that over time erode the rock .
what is corrosion or solution ?
acidic seawater causes alkaline rock to be eroded (eg limestone)
what is wave quarrying ?
breaking waves that hit the cliff face exert a pressure up to 30 tonnes per metres(2)
when are erosion rates the hiughest
-when waves have a long fetch
-during winter
-heavy rainfall occurs
-at high tide
-when waves approach the coast perpendicular to the cliff
igneous rocks examples/structure/rates
-granite/basalt
-interlocking crystals which allow for high resistance
-very slow, less than 0.1cm yearly
metamorphic rocks examples/structure/rates
-slate/schist/marble
-crystal all orientated in the same direction
-slow, 0.1-0.3cm yearly
sedimentary rocks examples/structure/rates
-limestone
-lots of fractures and bedding planes making them weak
-very fast, 0.5-10cm yearly
How is a cave/arch/stump formed ?
1-cliffs with joints faults and cracks are eroded more rapidly and erosion all processes exploit those weaknesses in the rock, deepening and widening weak points eventually forming a sea cave .
2-line of weakness extends right through the headland caves form on both sides.
3-marine erosion deepens the caves until they connect up,creating a complete tunnel through the headland and forming an arch.
4-hydraulic action and abrasion attack the sides of the arch between low tide and high tide, forming wave cut notches.
5-undercutting leads to the collapse of overlaying material by mass movement.
6-sub-Ariel processes attack the roof of the arch
7-roof collapses by by block fall leaving the seaward end of the headland detached from the land as a stack
8-erosion occurs at the base of the stack , forming a notch on all sides until rock collapses as block fall leaving a stump.
