Learning Objectives

1. Wind energy is transferred to water surfaces as waves. Wave height (distance from crest to trough) reflects wind speed, duration and distance. Wavelength is the distance between crests. Waves passing a point move water particles in a circular orbit. At the surface, diameter of the orbit equals wave height. At depth, effects of wave passage are lost below depths equal to half the wavelength.

2. Wave refraction is the change in direction along a wave crest as it comes in contact with the bottom while approaching shore. Wave refraction produces longshore currents that are parallel to the shoreline and transport considerable sediment parallel to the shoreline in the surf zone. Rip currents are perpendicular to shore and carry fine sediment offshore.

3. Beaches are strips of sand or gravel that extend from marine terraces offshore to cliffs or permanent vegetation zones onshore. The beach face is the steepest part and is exposed to wave action. The berm extends landward from the beach face.

4. Summer beaches have wide berms, while winter beaches have narrow berms and sandbars offshore. Most sediment on beaches was brought to the coast by rivers and streams. Damming free flowing rivers reduces sediment supply to beaches and promotes beach erosion.

5. Longshore drift is the movement of sediment parallel to shoreline by either swash and backwash along the beach face, or by longshore currents. Spits are fingerlike ridges of sediment deposited into open water. Baymouth bars extend from headland to headland cutting off bays from the ocean. Tombolos connect offshore islands to the mainland. All three depositional features reflect longshore drift. Jetties and groins are structures made by humans to interrupt sand being transported by longshore drift.

6. Coastal areas are classified as erosional, depositional, drowned, uplifted, or shaped by organisms. Erosional coasts are subject to coastal straightening (erosion on headlands and deposition in bays), and exhibit sea cliffs, wave-cut platforms, stacks and arches.

7. Depositional coasts have barrier islands, deltas, tidal deltas, and may preserve glacial deposits such as moraines. Fiords and estuaries are typical of drowned (submergent) coasts. Uplifted coasts exhibit uplifted marine terraces. Reefs and mangroves may shape coasts.