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Tides Longshore Drift 9613 - SC&H KS2 FactSheet - TIDES&WAVES-vB01 03/04/2012 14:12 Page 2 Suffolk Coast and Heaths www.suffolkcoastandheaths.org Coastal Knowledge Longshore drift Waves also transport sand and shingle along the shore, a process known as longshore drift. Waves often hit the shore at & an angle, depending on the direction of the wind. Longshore Tides waves drift has created features like Orford Ness and Landguard Point. Sometimes man tries to slow down longshore drift by building defences called groynes. “Hi I’m Marvin Moon. Did you know I act like a big magnet? Using the “Longshore drift moves sand sideways force of gravity, I pull the oceans towards me as the along the beach in a zig-zag pattern – this can earth spins. You see this as movement of water up sometimes cause sand to pile up on one side of and down a beach or in and out of an estuary. the beach! Look out for this next time These are called tides.” you go to the beach”. Things to do: See how currents Things to do: move sand Tides How tides are made Using the same You need 7 people and 7 When you’ve been at the beach, have you noticed tray and water add a balloons. 1 green balloon is the 1 that the water level changes? drop of ink or paint and earth, 1 white balloon is the blow and watch how the Sometimes it changes so much you may need to move moon, 1 yellow balloon is the ink moves. your deck chairs further up the beach as the tide sun and 4 blue balloons are the See how groynes work comes in! This is all because of the invisible attraction sea. The sun and earth stay in The amazing effect of the same place Using a clean tray and 1 Longshore drift can be acting between the moon and the earth, called gravity. 2water this time put a ruler and spin whilst half way across the tray and seen at Orford Ness As the Moon moves and spins around the Earth, gravity the moon moves around blow the paint towards the pulls – like a magnet - on the earth’s seas that are closest the earth ruler. See what happens! to it. This causes water to bulge towards the moon (see Longshore drift attracting diagram below) and a balancing bulge occurs on the the sea. Direction of opposite side of the earth. Of course, the continents get in Beach Have fun! movement the way, and the bulges of water can’t move smoothly Swash around the earth as it rotates. If you stay in one place you Backwash Waves Direction will normally see water levels go up and down, making high of waves and low tides, twice a day and just over six hours apart. Low tide 2 Moon Produced by EFMS Design & Print High High The Coastal Knowledge Fact Sheets have Sun been produced by the Suffolk Coast and Heaths tide tide AONB with co-funding from our partners. Photographs by Malcolm Farrow, Tony Pick, Rolando Ugolini and Mike Page Cartoons: Marvin Moon © Simon Reid. Gravitational Illustrations: Rolando Ugolini attraction Sun also has a Low tide www.suffolkcoastandheaths.org gravitational effect 9613 - SC&H KS2 FactSheet - TIDES&WAVES-vB01 03/04/2012 14:12 Page 4 Destructive waves Waves These are tall, steep waves that carry a lot of Things to do: energy. These waves hit the beach hard and Making waves As wind passes over the sea, it forces the water fast, with lots of water and energy, and can Get a tray and pour in water to surface to ripple, and eventually to form into waves. destroy the beach by washing beach material – cover the bottom then blow! As waves approach the beach, they touch against the sand and pebbles – away. See what happens? sea bottom, which makes them become higher and Large waves steeper until they finally break, creating the white hitting the beach water that rushes up the beach. The size of a wave is affected by the speed of the wind, and how long it blows for, how deep the water “Did you know is, and how great is the fetch – the distance the wind that the wind has travelled across open water. makes waves on We can recognise the difference between the sea?” constructive and destructive waves. Rocks protecting the beach Constructive waves These are small waves below one metre in height that are low in energy. As the wave breaks gently on the beach it Destructive waves at Slaughden taking carries sand and pebbles with shingle away it, which are then left behind as the tide goes out. This type of wave helps to put sand Large wave with back on the beaches. lots of energy Shingle pushed up Strong by small waves backwash Constructive waves leaving shingle Waves at Felixstowe behind at Hollesley Bay Destructive Wave Constructive Wave Larger in height, Smaller in height, more energy less energy Weak backwash: little or no erosion Strong swash: pushes shingle and sand up the Strong backwash: Weak swash: little or no beach building it up erodes the beach beach building.
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