The Dynamic OceanChapter 16

Ocean current-mass of ocean water that flows from one place to another

Surface currents movements of water that flow

horizontally in the upper part of the ocean’s surface

Upwelling rise of cold water from

deeper layers to replace warmer surface water

brings greater concentrations of dissolved nutrients, such as nitrates and phosphates, to the ocean surface

Density currents vertical currents of ocean

water that result from density differences among water masses

WavesWhere do waves

come from?The energy from

strong windsParts of a wave

A –crestB –troughC –wavelengthD –amplitude

Wave Period and SpeedWave period

the time it takes for a complete wave to pass a given point

Wave speedhow fast the waves

are travelingWavelength ÷

period

Factors that Affect the height, length and period of a wave

Speed of the windDuration

how long the wind will blow

Fetchthe length of water

surface over which the wind blows in a constant direction

BreakersSpilling breakers

over-steepened waves that are unstable and the top spills over. Occur on flat beaches.

Plunging breakersHawaii (large

splash)

Types of WavesWind wavesTsunamis

tidal waves formed by movements on a fault line

Internal wavesOccurs within the

water and not on the surface. “dead water”

TidesWhat are they and how do they work?

TidesWhat are Tides?

changes in elevation of the ocean surface

What causes Tides?Gravitational forces of the moon and sun

Tidal RangeVertical distance

between the high and low tides.

Vary from place to place and week to week.

Many factors (shape of the coastline, configuration of ocean basins, and water depth) influence tidal ranges.

Spring Tides

Spring TidesOccur during the new and full moons

All gravitational forces are added together

Extreme high and low tides

High tidal range

Neap TidesNeap Tides

During the 1st and 3rd quarters of the Moon

Gravitational forces are offset

Tidal range is the smallest value

TidesTides occur 50 minutes later due to …Rotation pattern of earth and moon.

This is known as a lunar day

Tidal PatternsDiurnal (daily)

one high and one low tide each lunar day. Occurs at Pensacola, Fl. And the Gulf coast.

Semidiurnal (semi-daily)2 high and 2 low tides:

each high and low tides are similar to the preceding high and low. Occurs in the Atlantic coast

Mixed2 high and 2 low tides

each day. Each high and low tides are different from each other. Occurs on the west coast.

Coast, Beaches and ShoresBeach

accumulation of sediment (sand and gravel) that occupies a portion of the shore. (moving)

Coastwhere the land meets the

sea.“lands edge that boarders

the sea”Shore

part of the coast in which the outer limits of wave action influences the land.

Forces that act on a shoreWave Impact

changes the shapeAbrasion

most intenseWave refraction

sediment transportation

Longshore transportworks with

refraction

Longshore CurrentsLongshore current

caused by waves which approach the shore at an angle –move sand grains along the beach (responsible for the beach erosion on the barrier islands)

Littoral drift the movement of sand

along the beach because of longshore currents

Rip CurrentsRip currents

water current formed when water moves to the sea through a break in an offshore bar.

Erosion FeaturesSea Arches

form when two caves are eroded and unite.

Spitelongated ridge of

sand that projects from the land into the mouth of a bay and hooks.

Erosion FeaturesTombolo

ridge of sand that connects an island to the mainland or another island.

Baymouth Barsandbar that has

completely crossed a bay, sealing it.

Barrier islandNarrow sandbars

parallel to, but separated from the mainland.

Protective StructuresGroin/Jetty

structures that are at right angles to the beach to trap sand.

Breakwater/Seawallstructures built parallel

to the shoreline to protect the coast from powerful breakers.

Bulkheadstructure separating

land and water areas –reduces erosion.

Beach NourishmentAddition of large

quantities of sand to the beach system