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Coasts - EQ 1 - Coggle Diagram
Coasts - EQ 1
The littoral zone
- the breakwater area, nearest to the coastline where high + low tides occur
Offshore: - the area of deeper water beyond the point at which waves begin to break. friction between the waves and the sea bed may cause some distortion of the wave shape
Nearshore - area of shallow water beyond the low tide mark, within which friction between the seabed and waves distorts the wave sufficiently to cause it to break (breaker zone) there may be a breakpoint bar between the offshore + nearshore zones
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Backshore - the area above the high tide mark, affected by wave action only during major storm events
Bedrock lithology
- the rate of coastal recession is influenced by the type of bedrock. It is influenced by how reactive the rock is to chemical, whether it is clastic + crystalline, whether it has cracks, fissures + fractures
igneous
- e.g. granite, dolerite, basalt
- erode + weather very slowly as have interlocking crystals, so are resistant
- contain few joints + weaknesses
Metamorphic
- e.g. marble, slate and schist
- recrystallised rock through heat + pressure. crystalline structure so is resistant but less than sedimentary
Sedimentary
e.g. sandstone, limestone, clay
- formed by compaction, least resistant type as are heavily jointed, they have weak structures
- have moderate erosion rates
Unconsolidated sediment
- e.g. not yet solid rock - alluvium
- not yet cemented + compacted. drifts due to deposition, and usually overlays bedrock
- very easily eroded at 2-10 meters per year
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Role of vegetation
- stabilises the coast - plant roots bind soil together, leaves + stems cover the grounds surface protecting it from LSD, wind, wave + tidal erosion
- coasts are harsh environments for plants due to : exposed nature of high winds, lack of shade, salt water submerging, sand lacking nutrients
- pioneer plants - first to colonise at a coastline - they modify the environment by stabilising sediment, add nutrients to soil, + reduced evaporation rates
- they create plant succession - the process of different plant communities occupying an area of the coast over time
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Classifying coasts
Short-term
- Energy inputs - tides, as well as currents, rivers, precipitation, gravity + tectonic - creates high + low energy coastlines - sediment inputs - deposition and erosion rates - deposition higher means expanding coastline, erosion higher mean eroding coastline - advancing + retreating - happens due to erosion + deposition, as well as emergent + submergence coasts linked with sea level
Long-term
- Geology - the lithology + structure, used to determine whether a coast is rocky, sandy or estuarine - and concordant or discordant
- sea level change - used to classify emergent + submergence coasts. tectonic plate movement can lift or submerge sections of land. climate change, causing sea level rise, can cause a coast to become submerging
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Concordant Vs discordant
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Discordant - differing layer of resistant and sock bands of rock - softer rock will erode faster than harder rock
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Complex cliff profiles
- produced where there are differing types of lithology. less resistant strata erode + weather quickly, producing wave cute notes.
- resistant strata erode + weather slowly, retreating less rapidly