Coastal Systems and Landscapes: Coastal landscape development Flashcards
(38 cards)
1
Q
How is a bay formed?
A
- Bands of hard and soft rock are eroded
- Soft rock erodes faster than hard rock
2
Q
How are tombolos formed?
A
- Bar or beach connects the mainland to an offshore island
- Formed due to wave refraction off the coastal island reducing wave velocity, causing the deposition of sediment.
3
Q
How are salt marshes formed?
A
- Spit is formed due to the longshore drift of sediment in low energy coastlines.
- The sediment projection creates a sheltered, saline environment where the flow of water is slower.
- Allows for silt and mud to be deposited in the sheltered estuary.
4
Q
How are spits formed?
A
- Longshore drift transports material along the coast
- Material is deposited due to reduction of energy where the sea meets the river
- Hook develops due to change in wind direction
5
Q
How are wave-cut notches and platforms formed?
A
- When waves erode a cliff, the erosion is mostly concentrated around the high-tide line .
- Hydraulic action and corrasion create a wave-cut notch
- As the notch becomes deeper, sub-aerial weathering weakens the cliff from the top.
- The cliff face becomes unstable and falls under its own weight by mass movement, leaving behind a platform of the unaffected cliff base beneath the wave-cut notch
- Over time the same processes repeat leading to a wave-cut platform to be formed.
6
Q
What is a raised beach?
A
Area of sand that is found high above the current beach
7
Q
Outline a dalmation coast:
A
Longitudinal coastlines that undergo submergence- formed when valleys parallel to the coast become flooded due to sea level change, leaving narrow and long islands parallel to the coastline.
8
Q
Outline a fjord:
A
- Glaciated U-shaped valley filled by sea water- formed when rising sea levels flood glacial valleys.
- Deeper in the middle section than at the mouth.
9
Q
Outline a Ria:
A
- A drowned river valley - formed when rising sea levels flood river valleys.
- Almost always estuaries
- Wide at mouth, water depth increases further inland.
10
Q
What is an emergence coastline?
A
Coastline that has emerged from the water
11
Q
What is a submergence coastline?
A
Coastline that has submerged below the water
12
Q
What are the two examples of emergence coastlines?
A
- Raised beaches
- Marine platforms
13
Q
What are the three examples of submergent coastlines?
A
- Ria
- Fjord
- Dalmation coastline
14
Q
What are the 3 main causes of isostatic sea level change?
A
- Uplift or depression of the earths crust due to accumulation or melting ice sheets
- Subsidence of land
- Tectionic processes
15
Q
What is the main cause of eustatic sea level change?
A
Tectonic uplift
16
Q
How does tectonic uplift cause eustatic sea level change?
A
Increases the volume of water.
17
Q
What are storm surges?
A
Occasions where meteorological conditions produce high winds and then higher wave levels than those at high tide.
18
Q
Define coastal sediment budget:
A
The balance between sediment being added to and removed from the coastal system
19
Q
How does wave refraction occur?
A
- Wave approaches the coast
- Wave drags in shallow water that meets the headland = increasing wave height and steepness, shortening the wavelength
-Wave in deeper water moves forward faster, causing the wave to bend. - Wave energy becomes concentrated on the headland, causing erosion.
20
Q
What is wave refraction?
A
The bending of waves as it passes from one medium to another.
21
Q
Outline how headlands are formed:
A
- Erosion (hydraulic action and abrasion) widens faults in the base of the headland, widening over time to create a cave.
- The cave will widen due to erosion and sub-aerial processes, eroding to the other side of the headland, creating an arch.
- The arch continues to widen until it is unable to support itself, falling under its own weight via mass movement, leaving a stack as one side of the arch becomes detached from the mainland.
- Eventually the stack will collapse into a stump
- A wave-cut platform will be left afterwards
22
Q
Outline how beaches are formed:
A
- Depositional landform that stretches from the high tide to the low tide.
- Created when sediment is deposited near the coastline when waves loose their energy.
- Beach accretion occurs when the beach is being built up by constructive waves.
- Beach excavation occurs in winter when destructive waves remove sediment from the beach.
23
Q
How do swash-alligned prevailing winds contribute to beach formation?
A
- Wave crests approach perpendicular to the coast so there is limited longshore drift- sediment doesnt travel far along the beach.
- Wave refraction reduces the speed of high energy waves, so a shingle beach with larger sediment is produced.
24
Q
How do drift-alligned prevailing winds contribute to beach formation?
A
- Waves approach at a significant angle, so longshore drift causes the sediment to travel far along the beach, leading to the formation of a spit at the end of a beach.
- Larger sediment is found at the start of the beach and weathered sediment moves further down the beach via longshore drift, becoming smaller.
25
What are berms?
Ridges which mark where the high tide line is at different times of the year.
26
What are cusps?
Small, curved dips in the beach where the swash comes in.
27
What are runnels?
Smaller ridges that are often found in smooth wet sand further towards the sea, caused by the tides.
28
How is a bar formed?
- A spit extends across a bay to join two headlands
- Water is trapped behind it forming a lagoon which is separated from the sea.
29
How are offshore bars formed?
(an offshore region where sand is deposited, as waves don't have enough energy to carry the sediment to shore)
- Waves break early, instantly depositing its sediment as loose sediment offshore
- Or, they can be formed as a result of backwash from destructive waves removing sediment from a beach.
30
Outline sand dune succession:
- Begins on dry, nutrient poor sand depostited by wind on high-energy coastlines.
- Embryo dunes are first colonised by pioneer plants, which die and release nutrients into the sand, decreasing the hostility.
- This allows for new species of plants e.g. Marram grass to colonise the land, which will progressively change the environment.
- A climax community will eventually form.
31
Outline salt marsh succession:
- Salt marshes form in low-energy coastal environments like estuaries, where fine sediment is deposited and forms mudflats.
- Pioneer species colonise the mud, trapping more sediment and starting succession.
- As more vegetation grows, conditions become less hostile (less salty and more oxygenated), leading to greater plant biodiversity and the development of a stable salt marsh ecosystem.
- A climax community will eventually form.
32
Outline estuarine mudflats:
- In river estuaries, the flow of river water meets the sea tides and waves, causing water flow to stop and for sediment to be deposited.
- As most of the sediment is small, this leads to a build up of mud, which overtime builds up until it is above the water level.
- Pioneer species colonise this area, causing more sediment to be trapped.
- A meadow is formed as sections reach above the high tide level, allowing for a climax community to form.
33
Outline isostatic sea level change:
- When the land rises or falls relative to the sea in a localised area.
- Often the result of glacial isostatic subsidence (when glaciers weight down the land beneath, so the land subsides.
- When the glaciers melt, isostatic recovery occurs and the coastline rebounds and rises again in the previous glacial areas.
- Tectonic activity e.g. earthquakes can also cause land subsidence, leading to isostatic sea level change.
34
Outline eustatic sea level change:
- Changes in sea level across the planet.
- Often due to thermal expansion- when water expands when it gets warmer, and so the volume increases leading to rising sea levels.
- Also due to changes in glacial processes.
35
Outline contemporary sea level change:
- Sea levels are continuously rising, due to thermal expansion and melting land ice (e.g. Greenland, Antarctica).
- Risen around 235mm since 1880 (start of industrial revolution).
- Predicited to rise to 0.3-1m by 2100 (depends on emissions).
- Has severe coastal impacts e.g. increased flooding risk (and storm surges), especially in low-lying areas like Bangladesh, saltwater intrusion.
- Adaptations to this increase have occured e.g. sea walls, retreat.
36
What is coastalisation?
- The process by which the coast is being developed and people are locating there, increasing the number of people at risk from marine related environmental activty.
- May be a byproduct of urbansiation, as many large cities are coastal.
37
What are storm surges?
- Result of the low pressure created by large weather events, like tropical storms.
- Sea level is raised- creates a flood risk, especially damaging following a tropical storm.
- Increased risk of SS occur by: removing vegetation- mangroves provide protection against extreme weather); global warming - as the surface of the oceans get warmer, it is predicted that the frequency and intensity of storms will increase, alongside SS and flooding.
38
How do coastal events contribute to environmental refugees?
- More than 1 billion people live on coasts that are at risk of flooding.
- Due to coastal events, e.g. flooding, people may loose their homes, culture and are forced to migrate to avoid the rising sea levels.
- E.g. in low-lying countries like Bangladesh where the coastline is made of clay, many people are displaced due to potential impacts of climate change on the coast.
