Tides

Question 1

Tides

Answer 1

Tides are the periodic rise and fall in the level of the sea caused by the gravitational pull of the sun and the moon.

Question 2

Explain the contrast in tidal ranges with spring and neap

Answer 2

There should be reference to the gravitational pull of both the sun and the moon, which when aligned give higher high tide and lower low tide, increasing the range. When the sun and moon are at right angles to the Earth, the gravitational pull is less effective rather than aligned and so the high tide is less and the low tide is higher, giving a smaller tidal range.

Question 3

Wave refraction

Answer 3

Wave refraction around headlands is capable of causing localised high/low energy coastlines with headlands exposed to intense erosion and bays being subject to very little wave energy.
. When waves approach a coastline they are refracted and become increasingly parallel to
the coastline
. As each wave approaches the coast, it tends to drag
in the shallow water which meets the headland
. This increases the wave height and wave steepness and shortens the wavelength
. That part of the wave in deeper water moves forward faster, causing the wave to bend
. The overall effect is that the wave energy
becomes concentrated on the headland, causing
greater erosion
. The low-energy waves spill into the bay, resulting in beach deposition
. As the waves pile against the headland, there may be a slight local rise in sea level that results in a longshore current from the headland, moving some of the eroded material towards the bays and contributing to the build-up of the beaches.

Question 4

Tidal range

Answer 4

The tidal range dictates how long wave processes can act on a cliff face for with a small range meaning they are focussed on the same area for longer and therefore capable of more erosion.

Question 5

Impacts of a large tidal range

Answer 5

. Horizontal movement of water often accompanies the rising and falling of the tide
. This is called the tidal current
. The incoming tide along the coast and into the bays and estuaries is called a flood current; the outgoing tide is called an ebb current
. The strongest flood and ebb currents usually occur before or near the time of the high and low tides, when water levels are close to their highest/lowest value
. The weakest currents occur between the flood and ebb currents and are called slack tides
. In the open ocean tidal currents are relatively weak. Near estuary entrances, narrow straits and inlets, the speed of tidal currents can reach up to several kilometres per hour
. These currents are much stronger and capable of transporting far more sediment if the tidal range is large as the amount of water moving is far greater
. As a result, a large tidal range is important for providing energy via tidal currents and in the transportation of sediment whilst a small tidal range is more important for concentrated erosion at the cliff base.

Question 6

High energy coastline

Answer 6

. Rocky coastline
. Erosion exceeds deposition
. Many examples in Cornwall
. In the UK often Atlantic facing
. Contains cliffs + headlands

Question 7

Low energy coastline

Answer 7

. Less powerful waves
. Sheltered areas e.g. bays
. Beaches and spits are found here
. Sandy and estuarine 
. Deposition exceeds erosion

Question 8

Spring tide

Answer 8

. Occurs when there’s a new or full moon
. Happens twice per month
. The moon and sun roughly aligned the tides of Earth are on average slightly larger than usual
. On beaches this can be seen when the water comes further up the shore than it usually does
. The tidemark left will be higher.

Question 9

Neap tide

Answer 9

. Follows seven days after a spring tide.
. Take please when the moon and sun are at right-angles to each other
. The effect of this alignment is that there is less difference between high and low water
. A high tide will be less high and a low tide will be less low, decreasing the difference between them.