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
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.