Coasts EQ1
- Created by: Yespacito
- Created on: 11-01-20 19:53
View mindmap
- Coasts EQ1
- Categorising Coasts
- Regions of the coast
- Backshore: only affected by waves during spring tides or storms
- Foreshore: between the high and low tide points, where most wave processes occur
- Nearshore: area of intense human activity eg. fishing. Forms part of sediment cells.
- Offshore: deep water away from land where offshore drilling occurs.
- Divisions of coasts
- Rocky coasts
- Has cliffs which can vary in height and lithology. Clear land - sea boundary
- Coastal plains
- Gradually slope towards sea - forms sand dunes and mud flats. Blurred boundary between land and sea
- Examples of contrasting coasts
- Flamborough head - rocky coast. Has wave-cut platform exposed at low tide with steep angle
- Belgian sand dunes: Beach submerged at high tide. Vegetation stabilises coast so erosion is reduced
- Estuarine coast at Lymington, Hampshire: Mud flats exposed at low tide, vegetation at backshore forms a salt marsh. Transition from land to sea more gradual
- Rocky coasts
- Criteria to classify coasts
- Formation processes
- Primary coasts dominated by terrestrial processes
- Secondary coasts dominated by marine erosion
- Relative sea change
- Emergent coasts rise eg. by tectonic uplift
- Submergent coasts sink eg. sea level rise
- Tidal range - distance between tides
- Microtidal is less than 2m
- Mesotidal is between 2 and 4m
- Macrotidal is more than 4m
- Wave energy
- If wind slow and fetch short, low energy
- If high energy, exposed and long fetch, high energy
- Formation processes
- Formation of different coasts
- Rocky coasts
- Steep cliffs dominated by marine erosion
- Unvegetated
- Little debris because it gets transported away.
- Shallower cliffs are dominated by sub-aerial processes
- Steep cliffs dominated by marine erosion
- Coastal plains
- Fall in sea level exposes seabed and deposition causes coastal accretion so coast moves seaward
- Dynamic equilibrium - inputs into a coastal system (eg. erosion) occur at the same rate as outputs (eg. deposition)
- Rocky coasts
- Regions of the coast
- Geological Structure
- Features of geological structure
- Strata: the layering of different types of rock
- Deformation: the degree to which the rock layers are twisted or deformed by tectonic activity
- Faulting: fractures that are caused by rocks moving from their original position
- Discordant coasts
- Rock strata run perpendicular to the sea
- Headlands and bays
- Soft rock erodes faster than hard rock, so the hard rock headland juts out while the bay is inland
- Effect on waves: in deep water, crests are parallel but as they approach a bay, they curve to fill the bay. This wave refraction means wave energy is focused on headlands
- Concordant coasts
- Rock strata run parallel to the sea
- Coves: water erodes through a fault/crack in the hard rock which then rapidly erodes the soft rock behind it, making a large area of water with a narrow entry
- Dalmatian coasts: tectonic activity forms a series of anticlines and synclines. During the Holocene period, eustatic sea level rise submerged most of the anticlines, just leaving the tops of the ridges behind, parallel to the coast
- Haff coasts: Sediment is built up parallel to the coast across a cove, forming a bar with a lagoon behind it.
- Cliff profiles
- Dip: angle of the rock to the sea, affected by tectonic activity
- Faults: A particular rock type is moved up or down by tectonic activity, and the layer is seperated
- Joints: the point where 2 rock strata meet
- Fissures: small cracks in rock that can be exploited by erosion
- Northumberland Heritage coast case study
- Cullernose point: a headland formed by hard rock being resistant to erosion
- Small caves form in layers of limestone after cracks are exploited by erosion
- Anticlines caused by tectonic activity
- Features of geological structure
- Factors affecting coastal recession
- Lithology
- Igneous: Slowly erode, interlocking crystals so resistant. Low jointing so few regions for exploitation by erosion
- Metamorphic: Slow, foliation (all crystals in one direction) so weaknesses. Often folded so erosion exploits
- Sedimentary: Fast, clastic (poorly cemented), fractured.
- Permeability of rock/cliffs
- If permeable, water can flow thru strata
- Water Pressure: water in strata exert pore water pressure, exerted by water above, so less stable so slumps
- Vegetation
- Halophytes: tolerate saltwater in roots, saltwater
- Xerophytes: Tolerate dry conditions eg. sand dunes
- Marram grass adaptations
- Tough, waxy, flexible leaves so resilient to sand blasting and limit water loss by transpiration
- 3m roots so tap water below surface
- Grow 1m per year, so keep pace with deposition of sand
- Plant succession
- Sand dune formation
- Specialised species grow (pioneer plants)
- Ends up as climatic climax community
- Sand dune ecosystem called psammosere
- Specialised species grow (pioneer plants)
- Salt marsh succession
- Gut weed binds mud
- Cord grass stabilises so mud accretion
- Salt marsh grass causes height increases
- Scurvy grass and rush develop profile
- Salt marsh grass causes height increases
- Cord grass stabilises so mud accretion
- Salt marsh ecosystem called halosere
- Importance of estuaries
- Sheltered from strong waves so deposition occurs
- Found at end of river so sediment transported to mouth and can be added at high tide
- Gut weed binds mud
- Sand dune formation
- Lithology
- Categorising Coasts
Comments
No comments have yet been made