Chapter 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

Waves



Where do waves come from?



The energy from strong winds



Parts of a wave



A –crest



B –trough



C –wavelength



D –amplitude

Wave Period and Speed



Wave period



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



Wave speed



how fast the waves are traveling



Wavelength ÷ period

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



Speed of the wind



Duration

 how long the wind will blow 

Fetch

 the length of water surface over which the wind blows in a constant direction

Breakers



Spilling breakers

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



Plunging breakers

 Hawaii (large splash)

Types of Waves



Wind waves



Tsunamis

 tidal waves formed by movements on a fault line 

Internal waves

 Occurs within the water and not on the surface. “dead water”

What are they and how do they work?

Tides



What are Tides?



changes in elevation of the ocean surface



What causes Tides?



Gravitational forces of the moon and sun

Tidal Range



Vertical 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 Tides



Occur during the new and full moons



All gravitational forces are added together



Extreme high and low tides



High tidal range

Neap Tides



Neap Tides



During the 1 st 3 rd and quarters of the Moon



Gravitational forces are offset



Tidal range is the smallest value

Tides



Tides occur 50 minutes later due to …



Rotation pattern of earth and moon.



This is known as a lunar day

  

Tidal Patterns

Diurnal (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 Mixed



2 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 Shores

  

Beach

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

Coast

  where 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 shore



Wave Impact



changes the shape



Abrasion



most intense



Wave refraction



sediment transportation



Longshore transport



works with refraction

Longshore Currents



Longshore 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 Currents



Rip currents

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

Erosion Features



Sea Arches

 form when two caves are eroded and unite. 

Spit

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

Erosion Features

  

Tombolo

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

Baymouth Bar

 sandbar that has completely crossed a bay, sealing it.

Barrier island

 Narrow sandbars parallel to, but separated from the mainland.

Protective Structures

  

Groin/Jetty

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

Breakwater/Seawall

 structures built parallel to the shoreline to protect the coast from powerful breakers.

Bulkhead

 structure separating land and water areas –reduces erosion.

Beach Nourishment

 Addition of large quantities of sand to the beach system