Unit 7 Waves Beaches Topic 1 Watching Waves

Unit 7 Waves & Beaches

Topic 1 Watching Waves n Surf zone is the area near shore where waves break. n How far from shore a wave breaks depends on the length of the wave and the depth of the water. n How a wave breaks depends on the: – – – steepness of the bottom slope whether the slope is smooth or irregular whether the bottom is composed of shifting sand or solid rock

n Waves may break more than once as they come to shore. n Each time it breaks, it gives up energy and becomes smaller and shorter.

Types of Breaking Waves n Plunging waves – Occurs when the swell comes out of deep water and hits a shallow sandbar or reef. – Form where there is a moderately steep, sloping bottom. – Form tubes or curls that cascade water in a circular motion downward into the trough and break forcefully with a rapid release of energy. – If the bottom is very steep, the top of the wave may break over the lower half forming a Collapsing wave with no curl. Ultimately, these are the waves that surfers look for. They break top to bottom and tend to be faster and more challenging.

n Spilling breakers – They form where the bottom slopes gradually. – These waves advance to shore with a line of foam down their front. – They break slowly over long distances – The wave energy is gradually released over time and the beach. – This type of surf is best for landing craft.

Break slowly Break rapidly

n Surging breakers – Steep beach slope – They form when large waves suddenly hit bottom in shallow water. – Wave does not break - surges up to beach n Example: Tsunami and tidal bores(occurs where a river empties into an ocean/sea. A tidal bore is a strong tide that pushes up the river, against the current. They are true tidal waves. A tidal bore creates a surge or a sudden change in depth. – which look like walls of water advancing toward shore.