Flashcards
Coasts
Flashcards do conjunto (44)
- 1How are waves created?By the wind blowing over the surface of the sea. The friction between the wind and the surface of the sea gives the water a circular motion
- 2What are constructive waves?Low frequency
Low
Huge
Weak backwash
Strong swash
Deposits material - 3What are destructive waves?High
Steep
Higher frequency
Strong backwash
Weak swash
Removes material from the beach - 4What is mass movement?Movement of material downhill due to gravity.
Landslides
Slumping - 5What affects the rate of erosion on a coastline?1. Fetch
2. Rock type
3. Aspect (dominant wind/wave)
4. Breaking point of waves
5. Width of beach - 6What is longshore dift?Currents move material along the coast
1. Swash carries sediment up the beach
2. Backwash carries sediment back down the beach, at right angles to the shoreline
3. When there's an angle between the prevailing wind and the shoreline, few rounds of swash/backwash moves up - 7How does a wave cut platform form?1. Weathering and erosion on a cliff cause a notch to form at high water mark
2. This notch eventually develops into a cave
3. Rock above the cave becomes unstable with nothing to support it and collapses
4. Flat surfaces are left behind - 8How do headlands and bays form?1. Where there are bands of alternating hard rock and soft rock at right angles
2. The soft gets eroded quickly = bay
3. The hard rock is eroded less = headland - 9How do caves, arches, stacks and stumps form?1. Weak areas in rock are eroded to form caves
2. Caves on the opposite side of the headland may eventually join up = arch
3. When an arch collapses it forms a stack
4. Further erosion and weathering = stump - 10How do blowholes form?Occasionally, the roof of a cave is weakened along a major joint by hydraulic pressure and the roof collapses to form a blowhole
- 11How are beaches formed?When constructive waves deposit sediment on the shore
- 12What are the two different types of beaches and their characteristics?1. Shingle - steep, narrow, larger particles and pile at steep angles
2. Sand - wide, flat and made of smaller particles - 13What are associated features with beaches?1. Berms- ridges of sand and pebbles found at high tide marks
2. Runnels- grooves in the sand running parallel to the shore
3. Cusps- crescent-shaped indentations that form on beaches of mixed sand/shingle - 14How do spits form?1. Longshore drift deposits material across the river mouth, leaving a bank of sand/ shingle sticking out into the sea
2. Occasional changes to dominant wind and wave direction may lead to a recurved end
3. Overtime, several recurved ends may be abandoned as waves return to their original direction - 15What forms behind a spit?The area behind the spit is sheltered from the waves and wind and often develops into mudflats and salt marshes
- 16How do bars form?1. Formed when a spits joins two headlands together
2. This can occur across a bay or across a river mouth
3. Lagoon forms behind the bar - 17How do sand dunes form?1. When sand deposited by longshore drift is moved up the beach by wind
2. Sand trapped by driftwood or berms is colonised by plants and grasses
3. The vegetation stabilises the sand and encourages more sand to accumulate there = embryo dune
4. Over time new dunes form = mature - 18How do salt marshes form?1. In areas of sheltered water
2. As silt and mud are deposited by the river or tide, mudflats develop
3. The mudflats are colonised by vegetation that can survive high salt levels
4. Plants trap more mud and silt and gradually creates an area of marshland - 19What is a case study for coastal erosion?Holderness
- 20What is eustatic sea level change?Effects always global
Caused either by change in the volume of water in the sea of by shape of ocean basin
- tectonic movements
- changes in climate - 21What is isostatic sea level change?Effects are local
Caused by vertical movements of the land relative to the sea
- Tectonic uplift
- Compression or decompression
- Subsidence of land due to shrinkage - 22Why is coastal flooding more likely now?Rising sea level
- 23What landforms are a result in coastline of submergence?1. Rias- river valleys partially submerged
2. Fjords- drowned glacial valley
3. Dalmatian coastline- valleys lie parallel to the coast - 24What landforms are a result in coastlines of emergence? (appears)1. Raised beaches- when the fall in sea level exposes wave cut platforms and their beaches
2. Relict cliffs- cliffs above beaches are no longer eroded and get covered slowly by vegetation - 25What are physical causes of flooding?1. Low pressure atmospheric systems
2. Strong onshore winds
3. Tidal currents and surges
4. High rainfall
5. Tsunamis - 26What are human causes to coastal flooding?1. Management of river systems
2. Management of coast systems
3. Building on coastal lowlands
4. Reclamation of coastal lowlands - 27What is the case study for coastal flooding?Tsunami, 26th Dec 2004
Southern Asia - 28What are the four options to coastal management?1. Hold the line
2. Advance the line
3. Do nothing
4. Retreat the line - 29What is the case study for soft engineering? (coastal)Blackwater estuary, Essex coastline
- 30What is the case study for hard engineering? (coastal)Holderness
- 31How does a sea wall work?The wall reflects waves back out to sea, preventing erosion of the coast. Acts as a barrier to flooding as well
- 32What are disadvantages to a sea wall?1. Expensive to build and maintain
2. Creates strong backwash which erodes under the wall - 33How do revetments work?Slanted structures built at the foot of cliffs. They can be made from concrete or wood. Waves break against the revetments which absorb the wave energy and so prevent erosion
- 34What are disadvantages to revetments?1. Create strong backwash which erodes under the wall
2. Expensive to build (cheap maintain) - 35How do gabions work?Rock filled cages
Absorb wave energy and reduce erosion - 36What are disadvantages to gabions?1. Ugly
but are cheap - 37How do groynes work?Fences are built at right angles to the coast. They trap beach material transported by longshore drift. This creates wider beaches which slow the waves down and gives greater protection from flooding and erosion
- 38What are disadvantages to groynes?1. Starve beaches down-drift of sand leading to greater erosion and flooding
2. Relatively cheap - 39What is beach nourishment?Where sand and shingle are added to beaches from elsewhere. This creates wider beaches
- 40What is beach stabilisation?Reducing the slop angle and planting vegetation to stabilise sand, this creates wider beaches
- 41What is land use management?Managing the land
e.g wooden walkways - 42What is creating marshland?From mudflats can be encouraged by planting appropriate vegetation, this stabilises sediment
- 43What is coastal realignment?Also known as managed retreat
Involves breaching an existing defence and allowing the sea to flood the land behind it. Overtime, vegetation will colonise the land and it'll become marshland - 44Why is soft engineering more sustainable than hard engineering?Hard engineering is often more expensive and disrupts natural processes, soft engineering tends to be cheaper requires less time and money to maintain. As well it integrates with the natural environment creating habitats (marshland), has a lower environmental impact and economic cost
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- Geography AS (Coasts) FlashCards sobre Coasts, criado por becca_walls em 09-05-2015.
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