EPS SCI 15 Lecture 9 Review

Important measures of ocean waves are:

• wave trough

• wave crest

• wave length

• wave height

• wave period

• wave speed

• wave frequency

Ocean waves are orbital progressive waves. The water molecules that make up the wave move in:

circles, or orbits, as the wave progresses.

Waves behave differently in “deep” water than they do in “shallow” water.

1. Deep water waves: depth > ½ length: ocean bottom does not affect wave.

2. Shallow water waves: depth < 1/20 length: ocean bottom strongly affects wave.

1. depth > ½ length: ocean bottom does not affect wave.

2. depth < 1/20 length: ocean bottom strongly affects wave.

Shallow-water waves begin to break when:

1. the ratio of wave height to wavelength is 1 to 7 (H/L = 1/7)

2. when the wave’s crest peak is steep (less than 120˚)

3. or when the wave height is three-fourths of the water depth (H= > 3/4 D).

Five factors influence the formation wind waves:

(1) wind strength

(2) distance of open water over which the wind blows

(3) width of area affected by fetch

(4) wind duration

(5) water depth.

The Beaufort Scale is:

an empirical measure that relates wind speed to observed conditions at sea or on land. It defines forces from 0 (no wind) to 12 (hurricane force).

Rogue or Monster Waves can form by:

merging waves or by waves and wind heading into a powerful current.

Tsunamis form by:

the displacement of a large volume of water caused by undersea earthquakes, erosion (slope failure), undersea volcano eruptions, or meteoroid impacts.

Tsunamis have a __________ (wave height) offshore, and a ______________ (often hundreds of kilometers long), which is why they generally pass unnoticed at sea. They grow in _____ when they reach shallower water, in a wave shoaling process.

small amplitude, very long wavelength, height

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by:

1. the Moon and the Sun

2. the rotation of the Earth

Local tides are influenced by many factors including:

1. the alignment of the Sun and Moon

2. the phase and amplitude of the tide

3. the shape of the coastline and near- shore bathymetry.

During full or new moons (Earth, sun, and moon are nearly in alignment) average tidal ranges are _________ (spring tide). During "half moon" (sun and moon are at right angles to each other = cancel each other out partially) moderate tides are produced (neap tides).

slightly larger