Tides and currents

What are tides

• Changes in water levels of seas and oceans

• When sea surface at its highest point high tide and when sea surface at lowest point low tide

• Difference between two points is tidal range

How do tides work

• Gravitational pull from Sun and Moon

• Moon pulls on Earth’s ocean causing water to bulge out towards moon

• Hight tide on side of Earth facing Moon and on opposite side as pulled slightly more strongly than the water on the far side

• Low tide in areas between bulges

What are spring and neap tides

• Spring tide: Moon, earth and sun in alignment so stronger gravitational pull creating high spring tide

• Neap tide: Sun and moon at right angle to earth so gravitational pull has reduced impact so lower than normal tides

How do tides cause erosion

• Large tidal range → means waves attack wider area of coast

• Small tidal range → erosion is concentrated in a narrower zone

What are tidal surges

Meteorological conditions create stronger winds which can produce higher water levels than those at high tide

What are tidal bores

When tide comes back in and water is funnelled up an estuary causing big waves

What are ocean currents

• They are continuous movement of water in a particular direction

• Located at sea level and below 300 metres of ocean

• Move vertically and horizontally occurring at a local and global scale

• Caused by wind, Earth’s rotation, differences in temp and salinity and gravity

What are longshore currents

When waves hit coastline at an angle to shoreline which generates a flow of water running parallel to shoreline . Creates a zig-zag movement of sediment called longshore drift

What are rip currents

These are strong currents moving away from shoreline which develop when seawater piles up on along coastline by incoming waves excess water then flows back out to sea through gaps in sandbars or weaker points in the breaker zone

What is upwelling

Movement of cold water, from deep in the ocean, towards the surface