Tides Flashcards
What are tides
Tides are the periodic rise and fall of the oceans surface.
How are tides formed
The moons gravitational forces pulls water towards it to make a high tide. The suns gravitational pull also pulls water towards it , but is less strong due to being further away.
Centrifugal forces help to create a compensatory bulge on the opposite side of the earth. In the areas between the bulges, tide is at its lowest
Why is there 2 high and low tides every day
Due to the earth spinning
What are the 2 types of tides
Spring and Neap tide
What are spring tides
When twice a month, the sun, moon and earth are aligned creating the highest of monthly tidal ranges
What are neap tides
When twice a month, the sun and moon are at right angles to each other, creating the lowest of the monthly tidal range.
Why are tides important
They are an important energy source as they transport sediment
They effect wave breaking position and therefore the coastline and its landforms
What is a current
The general flow of water in one direction
What are the 3 main types of current
Longshore currents
Rip currents
Upwelling
How do longshore currents occur
Waves hit the coastline at an angle rather than head on, so their water flows parallel to the shoreline, moving water and sediment along the surf zone
What are rip currents and how do they occur
Rip currents are strong, hazardous currents moving away from the shoreline.
They develop when seawater is piled along the coastline from incoming waves. They run parallel to the coast before moving outward in the breaker zone when the coast changes direction.
What is upwelling
Upwelling is the movement of cold water from the deep ocean up towards the surface. The dense cold water replaces the warm surface water to create nutrient rich cold currents
Key for forming the pattern of global ocean circulation currents
What is a sediment cell
A sediment cell is a well defined stretch of coastline with has little movement of sediment between each boundary
They are self contained closed systems
Give some features of sediment cells
There are 11 in UK and Wales, but large ones can be split into sub-cells like Flamborough head and the Humber estuary
They have prominent physical features such as headlands and bays
They are important when forming coastal management schemes
Where do sediment cell sources come from
5% erosion
5% offshore seabed
90% rivers
