Chapter 5: Coastal change and conflict

laurenclark90
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Mind Map on Chapter 5: Coastal change and conflict, created by laurenclark90 on 05/03/2014.

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laurenclark90
Created by laurenclark90 over 5 years ago
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Chapter 5: Coastal change and conflict
1 Geology of coasts
1.1 Soft rock coasts
1.1.1 clay - easily eroded by by the sea
1.1.1.1 Holderness, Yorkshire
1.1.2 cliffs
1.1.2.1 May be high but less rugged and steep than hard rock coasts
1.1.2.1.1 piles of mud + clay on cliff face
1.1.2.1.1.1 at foot of cliff - few rocks, some sand + mud
1.1.2.1.1.1.1 sea often brown
1.2 Hard rock coasts
1.2.1 granite - reistant to erosion
1.2.1.1 Land's End, Cornwall
1.2.2 cliffs
1.2.2.1 high, steep + rugged
1.2.2.1.1 bare cliff face
1.2.2.1.1.1 some rocks + boulders at foot
1.2.2.1.1.1.1 erosion features e.g. caves, arches, stacks
2 erosion
2.1 Hydraulic action
2.1.1 Waves hitting rock foces air into cracks. Trapped air, released quickly, breaks up the rock
2.2 Abrasion
2.2.1 Waves pick up stones and hurl them against the cliff which wears away the rock
2.3 Attrition
2.3.1 Pebbles carried by waves - rounder + smaller as they collide with eachother
3 Coastal landforms
3.1 At a headland
3.1.1 Cave - when waves erode weakness in the rock e.g. joint/fault
3.1.1.1 Arch - when 2 caves erode back from either side of a headland and meet in the middle
3.1.1.1.1 Stack - when the arch roof weathers and arch collapses
3.1.1.1.1.1 Stump - stack eroded by wind and water
3.2 wave- cut platform
3.2.1 1. waves cause undercutting at base of slope
3.2.1.1 2. forms a notch that gradually gets bigger
3.2.1.1.1 3. rock above loses support and collapses
3.2.1.1.1.1 4. debris gradually washed away by waves
3.2.1.1.1.1.1 process repeats - cliff slowly retreats backwards and becomes steeper
3.2.1.1.1.1.1.1 e.g. seven sisters, east sussex
4 Coasts
4.1 concordant coast - alternating hard and soft rocks occur parallel to coast and are eroded at different rates
4.1.1 formation of lulworth cove
4.1.1.1 1. waves slowly cut through weakness in resistant band of limestone - forms a small narrow entrance to cove
4.1.1.1.1 2. cove widens- soft clay eroded quickly
4.1.1.1.1.1 3. a band of chalk behind the clay is more resistant so erosion is slower
4.2 Discordant coast - alternating hard and soft rock occur at right angles to coast and are eroded at different rates
4.2.1 hard rock stands out as headlands and soft rocks form bays
5 waves
5.1 constructive
5.1.1 in calm conditions waves are
5.1.1.1 small, weak, low frequency
5.1.1.1.1 don't break with much force
5.1.1.1.1.1 add sand/ sediment to coastline by deposition
5.1.1.1.1.1.1 swash is greater than backwash so sediment is pushed up beach
5.1.2 long wavelength
5.1.2.1 shallow gradient
5.1.2.1.1 strong swash
5.1.2.1.1.1 weak backwash
5.2 destructive
5.2.1 break with lots of force + energy
5.2.1.1 have the power to carry out erosion of beaches + rocks
5.2.1.1.1 high frequency
5.2.1.1.1.1 backwash is greater than swash so sediemnt taken away from beach into sea
5.2.2 steep gradient
5.2.2.1 tall waves
5.2.2.1.1 short wavelength
5.2.2.1.1.1 weak swash
5.2.2.1.1.1.1 strong backwash
6 Longshore drift
6.1 1. waves approach the coast at an angle
6.1.1 2. Swash pushes sand and gravel up beach at same angle
6.1.1.1 3. Backwash carries sand and gravel back down beach at 90 degrees under force of gravity
6.1.1.1.1 4. sand + gravel move along beach in a zigzag fashion
6.1.1.1.1.1 5. sand is lighter so moves up the beach further than gravel or pebbles
7 Formation
7.1 spit
7.1.1 longshore drift carrys beach sediment beyond a bend in coastline
7.1.1.1 leading to an extention of the beach into the open water
7.1.1.1.1 end of spit becomes curved when exposed to srong winds + waves
7.1.1.1.1.1 deposition happens in the sheltered water behind then spit, and becomes a salt marsh
7.1.2 definition: material deposited by the sea which grows across a bay/river mouth
7.2 Bar
7.2.1 if longshore drift continues along the spit
7.2.1.1 over time, the sand + pebble accumulation grows larger and builds builds across an estuary to form a bar / join up with coastline on the other side
7.2.1.1.1 bar cuts off rivers from the sea so water builds up behind bar - forms a freshwater lake/ lagoon - e.g. slapton Ley, devon
8 Weathering
8.1 Mechanical
8.1.1 salt cystal growth (left from evaporated seawater) causes stress in rock - breaks into tiny fragments
8.2 Chemical
8.2.1 acid rain - reacts with weak minerals - dissloves + rock decays
8.3 Biological
8.3.1 roots of vegetation - grow in rock cracks + slit rock apart
9 Mass movement
9.1 rock fall
9.1.1 fragments of weathered rock from a cliff face fall under gravity + collect at base
9.2 Slumping
9.2.1 bottom of cliff eroded by waves
9.2.1.1 slope becomes steeper and cliff can slide downwards in a rotational manner
9.2.1.1.1 triggered by saturation due to rain
9.2.1.1.1.1 this lubricates the rock and makes it heavier
10 climate change on marine erosion + deposition
10.1 uk - rising sea levels as warmer temps. from global warming melt glaciers ans ice sheets
10.1.1 changing storm patterns - stronger + less predictable
10.2 impacts on marine erosion
10.2.1 stronger storms- bigger wave energy - more erosion
10.2.2 abandoned cliffs - come under new attack by waves as sea level rises
10.2.3 soft clay coasts - faster retreat
10.3 impact on marine depositional features
10.3.1 rising sea levels - beaches + bars at risk of submergence and erosion
10.3.1.1 e.g. Studland beach, Dorset - 1 million tourist p.a (eroded by 2-3m a year)
10.3.1.1.1 facilities relocate + beach replenished
10.3.2 extreme weather becomes more common - violent storms (+hurricanes)
10.3.2.1 destroy beaches/ spits
10.3.2.1.1 rising sea temp. - more storm energy - spits breached creating large gaps
10.3.2.1.1.1 e.g. 2004 hurricane charley - coast of florida - north captiva spit breached - 450m gap due to high tides + v. strong winds
11 climate change
11.1 Sea level rise - 0.3m prediction by 2100
11.1.1 loy-lying areas at risk e.g bangladesh + maldives
11.1.2 Thames estuary flooding - 12X more frequent by 2100
11.1.2.1 TTB - holds back v.high tides
11.1.2.2 'Thames estuary 2010' new project to build new flood walls along river
11.2 Storms at sea
11.2.1 increase height of waves - cause flooding
11.2.2 the environment agency manages + forecasts
12 How fast a coast retreats depend on ...
12.1 Rock type - hard rocks erode slower that soft
12.2 Number of faults + joints - with more the rocks erode faster
12.3 Fetch - if wind blows over a wide area of sea (fetch), the waves are stronger + will have a greater impact on cliffs
12.4 cliff exposure - ones exposed to strong winds + weather will erode quicker than ones sheltered
12.5 Storms - ones exposed to frequent storms erode quicker
12.6 Sea defences - those protected have a slow retreat
13 Cliff erosion effects
13.1 Houses destroyes
13.2 Farmland lost
13.3 loss of income
13.4 Hotels + caravan parks abandoned
13.5 loss of roads

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