Coasts Flashcards
Cliffs, wave-cut notch and wave-cut platforms
In areas of more resistant cliff material erosion is greatest when waves break at the foot of a cliff. This causes erosion at the base of the cliff.
* This creates a wave-cut notch in the base of the cliff. As the notch increases in size the weight of the
cliffs above become too much and the cliff collapses.
* The material from the cliff is broken up through attrition and some of it remains at the base of the cliff forming a terrace known as a wave cut platform.
Caves, arches, stacks and stumps
Even hard rock, that forms headlands, contains weaknesses. Hydraulic action forms cracks in the rock until an opening is formed.
* As the waves continue to attack the rock it is hollowed out to form a cave.
* Further erosion means that the cave is widened and deepened until it becomes an arch.
* Widening of the arch through undercutting means that material becomes unsupported and collapses
into the sea forming a stack.
* Further undercutting causes the stack to collapse leaving only a stump.
Formation of spits
A spit is a long beach made up of sand and
shingle that extends out to sea. It is found:
* In areas of shallow water.
* On a bend in the coastline.
* Eroded material is carried along the
coast by longshore drift. This action continues
until the prevailing wind and waves force the
spit to start to curve.
Holderness coast causes
Mostly comprised of boulder clay
The cliff foot erosional processes of hydraulic action and abrasion undercut the cliffs at their base and erode the soft material.
The strong currents of the North Sea rapidly transport material along the shore.
Most of Holderness is comprised of soft boulder clay, however, the northernmost part of the coastline is made up of chalk. Chalk is a more resistant rock and so less easily eroded.
Holderness coast effect
This has resulted in 14 villages being lost from the
coastline since Roman Times.
Ringborough Farm has lost 145 acres since 1939, meaning that half of the farm’s land has been lost to the sea. The farmer has also been forced to diversify
The rapid rate of cliff recession has meant that there has been a need to protect areas of high value with hard engineering defences e.g., the settlement of Hornsea on the Holderness Coast.
Without replenishment, Spurn Point may erode; this area is an SSSI (site of special scientific interest) and it is an important habitat for many bird species
Holderness coastal management
Use of groynes to trap moving beach material and provide a protective beach in front of the cliff
The construction of sea walls and revetments as wave-resistant structures at the base of the cliffs
Artificial off-shore breakwaters like tyres and concrete blocks, forcing waves to break off-shore.
Sea wall used to protect Easington Gas Station (cost 4.5 million)
Hurricane formation
Tropical storms begin when thunderstorms move over tropical ocean water.
* Tropical oceans (at least 27°C) warm the air above it.
* This warm, moist air starts to rise.
* Because this air is evaporating, there is less air left near the surface. This causes an area of
low air pressure.
* As the warmed, moist air rises and cools, the water in the air forms clouds.
* As the storm moves over the ocean, it picks up more warm moist air and grows. The speed of
its winds increases as more air is sucked in.
* Surrounding air rapidly moves into the low-pressure area to fill the space, causing wind speeds
to increase.
* The whole system of clouds and wind spins due to the trade winds and the earth’s rotation
(Coriolis effect).
* It can take hours or days to fully form a tropical storm. The eye is an area of calm winds, which
is surrounded by the ferocious eyewall of high winds and heavy rain.
Hurricane Katrina Impacts
*Katrina was a category 4 storm.
* Storm surges reached over 6 metres in height.
*New Orleans was one of the worst affected areas because it lies below sea level and is protected by levees. These protect it from the Mississippi River and Lake Ponchartrain. The levee defences were unable to cope with the strength of Katrina, and water flooded into the city.
*Despite an evacuation order, many of the poorest people remained in the city.
*People sought refuge in the Superdome stadium. Conditions were unhygienic, and there was a shortage of food and water. Looting was commonplace throughout the city. Tension was high and many felt vulnerable and unsafe.
*1 million people were made homeless and about 1,200 people drowned in the floods.
*Oil facilities were damaged and as a result petrol prices rose in the UK and USA.
Responses to the Katrina Hurricane
$50 billion in aid was given by the government.
The UK government sent food aid during the early stages of the recovery process.
The National Guard was mobilized to restore and maintain law and order in what became a hostile and unsafe living environment.
Coastal Opportunities and Threats on the US Gulf Coast
Tourism (20 million tourists annually)
Commercial fishing is a multi-million-dollar industry in the Gulf of Mexico, 146,000 jobs
Oil industry $31.3 billion generated
Ports
Tropical storms
Oil spills
Climate change
Where are coral reefs located
Coral reefs are located in tropical oceans near the equator.
* They are found 30 degrees north and south of the equator.
* The largest coral reef is the Great Barrier Reef in Australia.
* The second largest coral reef can be found off the coast of Belize, in Central America.
* Other reefs are found in Hawaii, the Red Sea, and other areas in tropical oceans.
What conditions do coral reefs need
They are generally found between latitudes 30 degrees Celsius north and south of the equator because this is where ocean temperatures are warm enough for them to survive. They cannot survive in water below 18 degrees Celsius and the optimum temperature for growth is 22-25 degrees Celsius.
* They require shallow waters (of up to 60m) so that light can reach the reefs allowing algae that live on the coral to photosynthesize (the coral feeds on algae)
* They require clear water with small amounts of suspended material – as this allows sunlight to penetrate and reach the coral. Also, if sediment settles on polyps, they are unable to feed.
* Corals cannot grow much above tide level because they need oxygen and food brought by breaking waves. They can’t survive for long periods exposed above the water.
* Corals grow best in conditions of high salinity as freshwater kills coral. For this reason, breaks in reefs often occur at river mouths.
The Great Barrier Reef
2012 km, at an offshore distance ranging from 10 to 100 miles.
Little annual variation in sea temperature, this has been important for the development of the reef as the optimum temperature for growth is 22-25 degrees Celsius.
400 types of coral, 1,500 species of fish and 4000 types of molluscs. It also holds great scientific interest as the habitat of species such as the dugong (sea cow) and the large green turtle, which are threatened with extinction.
Conditions needed for mangroves development
Mangrove trees thrive in hot, muddy, salty conditions that would quickly kill most plants.
* Temperatures – Most mangroves grow in warm waters within 30 degrees latitude of the equator.
* They only grow in areas where the temperature remains above 20 degrees Celsius
* They grow in calm, shallow, sheltered areas with no strong waves or currents.
* They develop in areas where there is a large area between the high and low water mark.
Characteristics of mangroves and adaptations
Mangrove swamps contain many different species of trees.
* Mangroves live in salty water as they are halophytes (salt tolerant plants).
* Mangroves are home to a diverse range of species including fish, birds, frogs, snakes, crocodiles, swamp rats, monkeys and tigers.
* Mangroves create a barrier to the shoreline and protect it from storms.
Salt-filtering roots that keep out much of the salt.
* Prop roots that help to hold the mangrove upright in the shifting sediments where land and water meet.
* Aerial roots that allow them to take in oxygen.
Mangroves also have salt-excreting leaves.
