Coasts- Lesson 3 Tides Flashcards
Currents are…
A source of energy in the coastal system.
Body of water moving in a definite direction
They are affected by local winds.
What are surface ocean currents?
Are driven by complex global wind system they are large circular currents
What are the three currents?
- Longshore currents
- Rip currents
- Upwelling
What are longshore currents?
They occur as most waves do, don’t hit the coast head in but at an angle. They transport material along the coast
What are rip currents?
Strong currents moving away from the coast. They develop when sea water is piled up along the coastline by incoming waves.
Met with resistance from the breaking waves, water returning back down the beach is forced just below the surface. The current may initially flow parallel to the coast before flowing out through the breaker zone. These can be hazardous to boats and people as this fast flowing offshore surge can drag people into deep water
What is upwelling?
The movement of cold water from the deep ocean towards the surface.
More dense cold water replaced the warmer surface water and creates nutrient rich cold ocean currents.
These currents form part of the pattern of global ocean circulation currents
What are tides controlled by?
Tides are controlled by the gravitational pull of the moon and sun. The moon has the greatest influence.
What does the gravitational pull of the moon do?
Causes the water to be pulled towards the moon, causes a high tide and a compensatory bulge on the opposite side of the earth
What are spring tides?
Bring the highest high tide and the lowest low tide
Moon, earth and sun are not n alignment
The greatest tidal range
What are neap tides?
Meal tides are when the moon and sun are positioned at 90 degrees to the earth
Experience the lowest high tide and the highest low tide , small tidal range
Sun and moon are working against each other
What is the tidal range?
The vertical difference between high tide and the succeeding low tide
Where are tidal ranges high and low?
They are high in parts of the British Isles and low in the Mediterranean
