2B.1 Flashcards
Define littoral zone
An area of coastline which has all sediment processes occurring sources, transport and sinks. A littoral cell is not a closed system
What does the littoral zone consist of
backshore, nearshore, offshore zones and includes a wide variety of coastal types - it is a dynamic zone of rapid change
OKAY NOW FRY BACON (SEA - OFFSHORE, NEARSHORE, FORESHORE BACKSHORE)
What is the backshore
- The upper beach closest to the land, including any cliffs or sand dunes.
- essentially from the mean high tide water mark up to a change in physiography (sand dune or cliff)
What is the foreshore
The lower part of the beach covered twice a day at high tide (the part of the beach that receives the most regular wave action).
- it includes the swash zone
What is the nearshore
- area from the mean low tide mark to beyond where waves break (hence called the breaker zone)
- this part of the sea is not exposed unless there is low tide unlike the foreshore which is exposed at both high and low tide
What is the offshore zone
- open sea
- further seaward than nearshore
- 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.
What is wave breaking
Waves break, but vary between high and low tide points
What is a wave
- Initially in open water, as energy transferred from air to water
- Shelving increases friction and wave breaks
What do rocky coasts result from and why?
Rocky coasts (high and low relief) result from resistant geology
WHY …
withstands erosive forces of sea, rain and wind, often in a
high-energy environment
What is resistance of a rock dependent on?
1) is rock clastic or crystalline?
2) how many cracks, fractures and fissures?
3) lithology of a rock
Why does clastic/crystalline factors matter to rock resistance
- sedimentary rocks like sandstone are clastic as they
are made up of cemented sediment particles, therefore are vulnerable to erosion, - igneous and metamorphic rocks are made up of interlocking crystals, making them more
resistant to erosion
why does the amount of fissures, cracks and fractures affect resistance of geology?
the more weaknesses there are in the rock
the more open it is to erosional processes, especially Hydraulic Action
Igneous; State examples, rate of erosion
examples: granite, basalt
ROE: v slow, less than 0.1 cm a year
SEDI; State examples, rate of erosion
example is limestone
ROE = very fast, 0.5-10 cm year
metamorphic ; State examples, rate of erosion
examples: slate, schist, marble
ROE = slow, 0.1-0.3 cm a year
Why does age of rock affect its resistance to erosion
- Ancient limestones have been compressed and compacted over millions of years = more resistant
- Recently erupted volcanic lava flows and tephra deposits tend to be weaker and easily eroded = less resistant
How does permeability affect resistance to erosion
- Permeability is important as groundwater flow can weaken rocks by exploit joint structures and binding materials.
- It can also create high pore water pressures within cliffs reducing stability
State examples of permeable and impermeable rock
Permeable rocks include sandstones and limestones
Impermeable rocks includes clays, mudstones and most igneous and metamorphic rocks
Describe unconsolidated material and how it is affected by erosion
- unconsolidated coastal material is the weakest and most easily eroded (due to lack of strength and subsequent exploitation by water).
- They tend to slump when saturated.
- consider if there are reactive Minerals in the rock (e.g. Calcite) – solution.
Define differential erosion
The selective erosion of areas of weaknesses
