Waves, Beaches, and Coasts

Prepared by Betsy Conklin for

Dr. Isiorho

Water Waves

• wave height: the vertical distance between the crest (the high point of a wave) and the trough (the low point of a wave)

• wavelength: the horizontal distance between two wave crests (or two troughs)

Surf• breaker: a wave that has become so steep that the

crest of the wave topples forward, moving faster than the main body of the wave

• surf: breaking waves

Wave Refraction• wave refraction: change in the direction of

waves due to slowing as they enter shallow water

Longshore Currents & Rip Currents• longshore currents: a moving mass of water

that develops parallel to a shoreline

• rip currents: narrow currents that flow straight out to sea in the surf zone, returning water seaward that breaking waves have pushed ashore

Beaches• beach: a stripe of sediment that extends from the low-

water line inland to a cliff or a zone of permanent vegetation

• beach farce: the section exposed to wave action

• marine terrace: a broad, gently sloping platform that may be exposed at low tide if the shore has significant tidal action

• berm: a wave-deposited sediment platform that is flat or slopes slightly landward

Longshore Drift of Sediment• longshore drift: the movement of sediment parallel

to shore when waves strike the shoreline at an angle• spit: a fingerlike ridge of sediment that extends out

into open water• baymouth bar: a ridge of sediment that cuts a bay

off from the ocean which is formed by sediment migrating across what was earlier an open bay

• tombolo: a bar of sediment connecting a former island to the mainland

Longshore Drift of Sediment (cont.)

Erosional Coasts• coast: all the land near the sea including the

beach and a strip of land inland from it

• headlands: point of land along a coast

• coastal straightening: the gradual straightening of an irregular shoreline by wave erosion of headlands and wave deposition in bays

Erosional Coasts (cont.)• sea cliffs: steep slopes that retreat inland by mass

wasting as wave erosion undercuts them

• wave-cut platform: a horizontal bench of rock formed beneath the surf zone as a coast retreats by wave erosion

• stacks: erosional remnants of headlands left behind as the coast retreats inland

• arches: bridges of rock left above openings eroded in headlands or stacks by waves

Erosional Coasts (cont.)

A

B

C

D

Depositional Coasts

• barrier islands: ridges of sand that parallel the shoreline and extend above sea level

A barrier island near Pensacola, Florida

Drowned Coasts• estuary: drowned river mouth

• fiord : glacially cut valleys flooded by rising sea level

An estuary formed as rising sea level drowned a river valley, Malibu, California

Uplifted Coasts• Uplifted coasts have been elevated by deep-

seated tectonic forces. The land has risen faster than sea level, so parts of the old sea floor are now dry land.

Uplifted marine terrace, northern California. The flat land surface at the top of the sea cliff was eroded by wave action,then raised above sea level by tectonic uplift. The rock knob on the terrace was once a stack

Pictures

All pictures used in this power point presentation were taken from the following:

Carlson, Diane H., David McGeary and Charles C. Plummer. Physical Geology: Updated Eighth Edition. New York City, McGraw-Hill Higher Education, 2001.