Coastal systems Flashcards
Look at coastal zone Sheet
.
What are tides
Tides are periodic rises and falls of large bodies of water caused by the gravitational interaction between the Earth and the Moon
How do tides form
The gravitational attraction of the moon causes the oceans to bulge out in the direction of the moon. Another bulge occurs on the opposite side, since the earth is also being pulled towards the moon
Three Coastal effects of Tides
1) The change in water level results in different parts of the foreshore being exposed to wave energy throughout the day.
2) Tidal currents themselves can erode and transport sediment. Generally, Tidal currents become stronger near the coast and play an important role in circulation.
3) Tides cause the draining and filling of tidal bays and contribute to the build-up of mudflats.
What are spring tides
Are especially strong tides. They occur when the Earth, the sun and the moon are in line. The gravitational forces of the moon and the sun both contribute to the tides. Occur during full moons.
What are neap tides
Are espcially weak tides. they occur when the gravitational forces of the moon and the sun are perpendicular to one another. Occur during quarter moons
Pattern of ocean currents
Warm currents move away from equator, cold currents moving towards equator.
Currents move clockwise in northern hemisphere, currents move anti-clockwise in southern hemisphere.
Earths rotation affects wind patterns, Coriolis effect.
What is wind
Wind is the movement of air from an rea of high pressure to an area of low pressure. The greater the pressure gradient the faster the winds.
What causes waves
The wind dragging water on the surface of the water, the length of water the wind blows over is called the fetch
Explain wave formation
- The water becomes shallower and the circular orbit of the water particle’s changes to an elliptical shape.
- The wavelength and the velocity both decreases, and the waves height increases- causing water to back up from behind and rise to the point where its starts to topple over.
- The wave rushes up the beach as swash and flows back as backwash.
Constructive wave characteristics
Low and flat, strong swash, weak backwash, net beach sediment gain, low frequency waves.
Destructive wave characteristics
High and steep, weak swash, strong backwash, high frequency, net beach sediment loss
Explain the thermohaline circulation
In Earths polar regions ocean water gets very cold, forming sea ice. As a consequence the surrounding seawater gets saltier, because when sea ice forms, the salt is left behind. As the seawater gets saltier, its density increases, and it starts to sink. Surface water is pulled in top replace sinking water, which in turn eventually becomes cold and salty enough to sink. this initiates the deep ocean currents driving the global conveyor belt.
Sources of sediment
Rivers, cliff erosion, LSD, wind, Glaciers, offshore sediment.
What are sediment cells
Is a stretch of coastline, usually bordered by two prominent headlands, where the movement of sediment is more or less contained. It is therefore a largely close system.
