Introduction To the Oceans
•About 71% of the surface of the planet is
covered in salt water.
•Beneath the depth averages 3,8 km giving it a volume of 1370 x 106 km3.
•Since life exists throughout this immense
volume, the oceans constitute the single largest repository of organisms on the
planet.
Introduction To the Oceans
•These organisms include representatives
of all phylums and are tremendously varied but all
are subject to the properties of the sea water that surrounds them.
• Many features common to these plants and
animals are the results of adaptations to the watery medium and its movements.
Introduction To the Oceans
•Its
necessary therefore, to examine the physical and chemical conditions of
seawater and aspects of its motion (oceanography) and look at the environment
where the organisms live.
Introduction To the Oceans
Hydrologic
(Water) Cycle
Introduction To the Oceans
Where is all
the Water?
Introduction To the Oceans
Ocean Basins
Introduction To the Oceans
Ocean Basins
Introduction To the Oceans
•The mean depth is 4km (2.5 miles)and its interconnected from the Arctic to Antarctic.
•Seawater flows freely among the basins
transporting dissolved materials, heat and marine organisms.
•Seawater mixes from basin to basin/per
1000 years but regional characteristics of the seawater do exist.
Introduction To the Oceans
•The major basins are the Pacific, Atlantic,
Indian, Arctic, Southern ocean and the boundaries are artificially defined.
Introduction To the Oceans
•Seawater mix
•Movement of water moderates world climate
by distributing heat from equatorial water to the poles.
•Warm currents flow toward the poles from
the equator (Gulf Stream) heating northern latitudes.
•Cold water from the Arctic and Antarctic
basins flow beneath the oceans surface toward the tropics...cooler water near
the equator.
Introduction To the Oceans
•SEA LEVEL
•The sea level has undergone dramatic
changes. 15000 years ago 120m below present level.
•As it fell portions of the continental
shelf were exposed changing position of coastline.
•Ice age/Wisconsin glacial period, the
ocean water froze into glaciers.
Introduction To the Oceans
•SEA LEVEL
Introduction To the Oceans
•It is still rising.
•The rise slowed 3000 years ago and has
only risen 10m since.
•CO2 is warming the Earth and the ice could
melt and flood low lying areas in the next 1000 years.. Green
House effect.
Introduction To the Oceans
•The Ocean Floor
•Prior to the 1920's, they used weighted
rope to probe depths.
•1920's the echo sounder (SONAR-(sound
navigation and ranging) which analyzed sound waves which bounced off the oceans
bottom and returned to the ship.
•The Meteror
(1925-7) did the 1st ocean survey with sonar.
Introduction To the Oceans
•Common topographical features of the
oceans include: Continental margin and deep sea as the major divisions.
Continental Margin
•Continental
shelf-underwater extension of the continental land mass.
• 8% of the total surface area of the
world ocean, yet its one of the most productive parts of the ocean.
•It gradually drops down to the 100-200m
depth.
Introduction To the Oceans
•Formation of Continental Shelf
Introduction To the Oceans
•Continental slope begins where
continental shelf plunges down.
•As the steepness decreases, this zone is
called the continental rise.
Introduction To the Oceans
•Locations of Continental Shelfs
Introduction To the Oceans
•Soft sediment of the shelf exposed to
erosion from rivers and then the glaciers started to melt,
excess water cut canyons into the shelf.
• Ocean refilled, flooding shelf and
forming underwater canyons.
•The rise slowed 3000 years ago and has
only risen 10m since.
Introduction To the Oceans
•Underwater canyons occur in the margins
which resulted from when the
ocean level was lower with rivers flowing over them eroding the
soft sediments making deep gouges.
• Underwater landslides along the sides of
the canyons make the canyon bigger
Introduction To the Oceans
Introduction To the Oceans
•Types of Reefs
•Fringing-along the land
•Barrier-a lagoon between the land and
reef
•Atoll-a reef around a lagoon (formally an
island since eroded.
Introduction To the Oceans
•Types of Reefs
Introduction To the Oceans
•Trench
Formation
• Converge: one plate
dives under another, crumples and forms trenches...
Introduction To the Oceans
•Turbidity Currents
•Avalanche-like sediment movements caused
when turbulence mixes sediments into water above a sloping bottom.
•Since this sediment-filled water is now
denser than the surrounding water, thick, muddy water can run down the slope at speeds up to
17mph.
•These currents may have been responsible
for enlarging submarine canyons
Introduction To the Oceans
•Turbidity Currents