IB Geography Oceans and Coastal Landforms

• They are cause by the influence of prevailing winds blowing steadily across the sea

• The main pattern is roughly circular.

• Clockwise in northern hemisphere

• Anti-clockwise in southern hemisphere

Ocean currents move cold, nutrient rich water from the ocean floor to the surface. Eg. Found off the coast of Peru.

This supports fisheries, however the upwelling off the coast of Peru disappears during El Nino

The reversal of normal atmospheric circulation in the Southern Pacific Ocean. This warms the East Pacific.

The intensification of normal conditions, strong easterly winds push cold, upwelling water off the coast of South America into the Western Pacific

Near South America, winds blow offshore causing upwelling. Warm surface water is pushed into the Western Pacific. This causes high pressure, low temperature and low rainfall in South America. And causes low pressure, high temperatures and high rainfall in the Western Pacific.

High pressure over western pacific, and low rainfall

Low pressure over South America, causes high rainfall

Intense low pressure systems which bring heavy rainfall, strong winds, and high waves. This can cause flooding and mudslides. They usually originate over tropical seas.

• Sea temperatures over 27 degrees

• Warm water must have a greater depth than 60m

• The area must be far enough from the equator that the coriolis effect takes place.

• The largest Co2 sink

• Photosynthesis turns carbon dioxide into organic material. This material, over time, settles into the deep ocean.

Caused by man-made sources. Oceans absorb carbon which becomes carbonic acid. This lowers the pH of the ocean. This can kill off coral reefs and shellfish beds by reducing calcification. This results in slower growth and weaker skeletons

Constructive waves

• Depositional

• Long wavelength, low height

• Low frequency

• Swash greater than backwash

Destructive waves

• Erosional

• Short wavelength, high height

• High frequency

• Backwash greater than swash

Salt weathering

• salt compounds expand in joints and cracks, weakening rock structures

Freeze-thaw weathering

• Water freezes, expands and degrades jointed rocks

Biological weathering

• Carried out by molluscs, sponges and urchins

Tidal range controls vertical range of erosion, deposition and biological activity. It can also have a scouring effect.

Mass movement

• Provides large amounts of material which can bury beaches and protect cliffs

Rivers

• Carry sediment to coast

Periglacial processes

• Provide frost-shattered shingle for beaches

Erosion of cliffs

• Provides material for beach building, may also protect the cliff from further erosion

Wind erosion and transport can carry fine sand

Volcanic activity can produce dust and ash for beaches.

A low resistance rock will make a weak coast as they are easily eroded and won’t support an overhang. Jointing may also cause weakness. The amount of undercutting, and sub-aerial processes also affect the cliff profile.

Steep cliffs are replaces by a lengthening platform which then lowers cliff angles. This can be caused by sub-arial processes, erosion and weathering.

Lines of weakness can be eroded to form enlarged caves, if this breaks through a headland it is called an arch. Then if the roof of the arch collapses due to weathering and erosion it becomes a stack. The eventual erosion of the stack makes a stump

A spit is a beach of sand/shingle which is connected at one end to land. They have a thin attached end (distal end) and a larger (distal) end, which may be curved due to wave refraction. These occur as a result of longshore drift.

A global change in sea level. Sea levels change in connection with the growth and decay of ice sheets.

The localised change in the level of the land relative to the level of the sea. This could be caused by tectonic uplift.

• Temperatures decrease, glaciers and ice sheets advance and sea level falls eustatically

• Ice thickness increases so land is lowered isostatically

• Temperatures rise, ice melts, sea levels rise eustatically

• Melting releases pressure on the land so land rises isostatically

• Where the rate of erosion exceeds the rate of deposition

• Includes submerged coasts

• When deposition is rapid

• Includes emerged coastlines

Raised beaches

Coastal plains

Relict cliffs

Raised mudflats

drowned river valleys

fjords

drowned glacial lowlands

Embryo dune → Yellow dune

Yellow dune → Semi-fixed dune

Semi-fixed dune → fixed (gray) dune

Sea couch grass can colonies a small embryo dune formed by wind blowing sand up the beach, above the seaweed strand line.

Once the dune starts growing, marram grass can colonise which can grow it into a yellow dune.

When the dune is very high, less sand builds up behind, so marram grass dies and soil begins to form which means other plants can grow, this creates the semi-fixed dune.

As time goes on and soil becomes richer and more developed, lichens, mosses etc form a continuous layer over the dune forming a gray dune.

They protect coasts against erosion and provide a habitat for many different species of fish. They generate large profits in tourism, for diving and adventure.

Marine protected areas, which can restrict harmful activities such as oil drilling, fishing and mining. Another major harmful impact is fishing vessels which need to be restricted.

Salt-tolerant forests of trees and shrubs which grow in tidal estuaries and coastal zones of tropical areas. The muddy waters are rich in nutrients.

They provide fuelwood, charcoal, dyes, poisons and shellfish. Many species of fish use mangroves as nurseries.

Management strategies include restoration and afforestation, managed realignment allowing mangroves to migrate inland. And general protection.

An area in which a coastal nation have sovereign rights over all the economic resources in the sea, up to 200 nautical miles from the coast.

Compounds which usually consist of methane molecules trapped in water. Some scientists believe they contain more energy than all known fossil fuel deposits.

In the continental shelf. Most oil and gas reserves are in the Persian gulf

The worlds supply of fish has dramatically increased. Africa was the lowest consumer, and Asia the greatest.

Fishing industry, the use of boats for shipping, offshore mining and extraction and illegal dumping.

Discharge from stormwater drains, industrial outfalls, untreated sewage, littering and landfills.

It comes from nuclear power and industrial uses. After the explosion of the nuclear power station at Fukushima, nuclear waste was carried across the northern pacific ocean to USA and Canada. Nuclear waste remains radioactive for decades.

Great pacific garbage patch- Containing approx. 100 million tones of garbage suspended in two gyres. It can take centuries for plastic to decompose. Marine wildlife inadvertently eat it, which causes death usually.

Ships burn bunker oil which causes death from chest and lung infections and cancer. Oil spills cause massive ecological disaster.

UN Law of the Sea implemented regulations on deep sea mining and EEZ’s.

A series of international laws eliminated the discharge of toxic materials into waters around Europe.