Unit 7 Waves & Beaches

Topic 1 Watching Waves Surf zone is the area near shore where waves break. How far from shore a wave breaks depends on the length of the wave and the depth of the water. 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

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

Types of Breaking Waves 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.

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

Surging breakers Steep beach slope They form when large waves suddenly hit bottom in shallow water. Wave does not break - surges up to beach Example: Tsunami and tidal bores which look like walls of water advancing toward shore.