Coastal Processes Compression : Air is trapped between the waves and a cliff. This is compressed & driven into cracks in the rocks causing great pressure . As the wave retreats it results in sudden decompression. This activity weakens the rocks.
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Compression : Air is trapped between the waves and a cliff. This is compressed & driven into cracks in the rocks causing great pressure. As the wave retreats it results in sudden decompression. This activity weakens the rocks.
Longshore drift: waves approach the beach at an angle, driven by the wind. Run up the beach at an angle and returns at a right angle… zig zag pattern. The swash carries sediment up the beach and the backwashcarries it down the beach. This causes movement of sediment along the beach.
Abrasion: Boulders, pebbles and sand pounded against coast
Hydraulic Action: Impact of waves
Attrition: Stone rounded off by impact
Plucking: Meltwater penetrates cracks in the rock. This freezes & expands weakening and fracturing the rock. The galcier attaches itself to this rock and as it moves it pull or plucks the rock away. Assisted by freez thaw action.
Abrasion: Rocks attached to side & bed of the galcier scour, scrape & polish the surfaces they come in contact with. These cut scratches & grooves in the bedrock, called striae, which indicate the direction of movement of the galcier.
Basal slip: The sliding movement of a glacier over its rock flour. (rocks crushed by the glacier)
Freeze-thaw: Breaking of rock due to repeated freezing of water
As waves approach shore it gets shallower so friction with the bottom increases
As the cliff retreats inland it exposes rock underneath with a gentle seaward slope called a wave cut platform
If this platform gets too big the waves lose all there energy before reaching the cliff the cliff becomes inactive and erosion ceases to occur
This can be seen by vegetation growing on the cliff and debris collecting at the bottom
Vertical cliffs occur in areas of uniform rock or where strata dip inland
The foreshore is lower, gentle gradient and consists of sand, mud and shell particles
Sandspits are long narrow ridges of sand and shingle that are attached to land on one side
Formed by longshore drift when coast changes direction sharply
Sediments carried off shore and deposited on sea bed building up to form spit
Continues to grow as long as deposition is greater than erosion
Sand dunes may from on sheltered landward side and beach formed on seaward side
End can often be recurved due to change in wave direction
Salt marsh can also develop on the landward side
E.g. Strandhill co sligo
Tombolo is a spit that connects an island to the shore e.g. Howth linked to Sutton Island