Coasts and Oceans

Oceans cover almost 3/4 (70%) of the Earths surface.

Although reference is made to 5 oceans (Atlantic, Pacific, Indian, Arctic and Antarctic) really only one world ocean.
[Smaller area with restricted access are called seas : Caribbean, Mediterranean, Red etc]

Majority of worlds popolation lives within a few miles of the ocean, therefore an important to understand especially the coastal (littoral zone).

Coasts: the edge of the sea:

Two factors affecting cosatal processes: waves and tides

Waves

Generated by wind blowing over the oceans - swell

Motion of water in waves

V = velocity of wave, L= wavelength, T= period of wave, then

V = L/T

Surf zone - when waves approach shore the wave "feels bottom" and this interaction deforms wave

swash

backwash

Wave Refraction

Longshore current

Tides

Effect of gravity of Moon on ocean "envelope"

two tides every 25 hours ie.one tide every 12 1/2 hours.

Also effect of Sun on tides

Spring tide Neap tide

Sediment dynamics on shorelines

Where land meets sea - can be beaches (dominated by deposition), backed by dunes; or rocky coastlines

Beaches - deposition in littoral zone

Structure of the beach:

offshore foreshore backshore dunes

Longshore currents and longshore drift

Sand budget of beach

Some depositional landforms

Sand bars

spits and tombolos

barrier islands

Erosion on a sandy shore

Interruption of beach budget - example of Miami Beach

How to fix erosion?

1. slow it down - groins

2 replace sand - beach repleshinment

Rocky shorelines - effect of sea level

Influenced v. much by changes in sea level (uplift of land and/or drop of sea level)

Emergent Coastlines on a rocky shore

Emergent shorelines (outside of tropics) dominated by erosion.

Fall of sea level produces rocky , cliff-like shorelines with

cliffs, wave cut platforms, and notches

Arches, stacks etc

Submergent coastines

Rias

Fjords

Emergence and submergence on tropical coastlines - role of coral reefs

How reefs grow

Warm, clear (shallow) water - fringing reefs

Emergence - raised reef terraces

Submergence - barrier reef and atolls

DEEP OCEAN

Continental Shelf, rise and slope

shelf - less than ~200m deep

rise

slope

Submarine canyons cut shelf edge

Turbidity currents

Abyssal ocean floor

5000 m depth

Pelagic sediment - foraminiferal oozes, wind-blown clays

Carbonate compensation depthe 4000m

Mid ocean ridges and fracture zones

Deep sea trenches and island arcs

related to subduction zones

Seamounts, Guyots and Mid- ocean islands

Related to hotspots ?

Seamounts

Guyots - flat topped

Atolls