Download The Sea Floor

The oceans cover
71% of the earth’s
surface
The Four Large Ocean Basins
The Arctic Ocean


Shallow
Low Salinity




Diluted by large rivers
About half covered with
permanent ice
Low species diversity
Hallmark animals include
polar bear and walrus
Walruses were once common around the
perimeter of the Arctic, but large-scale hunting has
greatly reduced their numbers
Features of Atlantic Ocean

Georges and Grand
Banks


Great expanses of
shallow water that
supported cod
fisheries for
centuries
North Sea

One of most
thoroughly studied
marine waters on
earth
The Manatee
(36,163 ft.)
The Pacific Ocean
Feb 1977 the submersible Alvin dived
to a depth of 2500m over the Galapagos
ridge. That is when hydrothermal vents
were discovered.
The Galapagos Ridge
Equator
The deep sea submersible Alvin
Hydrothermal Vents
Water is
heated
by magma
and absorbs
metals from
earth’s crust
Marine Iguana
The Indian Ocean: Relict Species

Coelacanth
 Stromatolites
Drive from Perinet to Toamasina.
Fly to Maroantsetra. Drive to Relais
du Masoala Hotel. Two hour boat
Ride to Ecolodge on Masoala
Peninsula.
Hotel
Ecolodge
The Four Large Ocean Basins
The Ocean Basins Are Interconnected
The World Ocean

The Antarctic
Circumpolar Current
(ACC)


The
Southern
Ocean

Formed about 25 MYA
when Australia and
South America
separated from
Antarctica
Isolated the Antarctic
continent from warmer
waters to the north and
is partially responsible
for the formation of
Antarctica's permanent
ice cover.
The northern boundary
is called the Antarctic
Convergence or the
Polar Front.
The Southern Ocean

Antarctic Convergence


Divides warm surface
waters of Atlantic,
Pacific, and Indian
Oceans from cold polar
waters.
Abundant krill
 Summer feeding area
for baleen whales
Large Scale Distribution of
Antarctic Krill
The Antarctic Convergence
Krill are a keystone species in
the Antarctic food web. Krill are
crustaceans with several larval
stages in their life cycle. Some of
the larval stages feed on algae that
grow on the lower surface of sea ice.
One of the factors that determines
the annual abundance of krill is the
extent of sea ice in winter. Global
warming may have significant
impacts on krill abundance.
Baleen Whales
Crabeater Seals
Leopard Seals
Adelie Penguins
Chinstrap Penguins
Gentoo Penguins
Krill – Euphausia superba
Phytoplankton
The Sun
Light E
Photosynthesis
Food E
The top
predators of the
Antarctic
Peninsula are
seabirds and
seals.
The Crabeater Seal is a Krill Specialist
Crabeater seals are krill specialists.
Their entire “terrestrial” existence is
spent on ice floes, not land. Their
populations may be increasing due to
an increase in krill abundance associated
with the decline of baleen whales.
The Structure Of The Earth

Core





Mostly iron
High Temperature
Solid inner and liquid
outer core
Swirling motion of
liquid outer core
believed to be what
creates earth’s
magnetic field
Polarity reversals
about every 300,000
years
The Structure Of The Earth

Mantle




Solid
High temperature –
Near the melting point
of rocks
It flows
Iron and magnesium
silicates
The Structure of the Earth

Crust



Outermost layer
Extremely thin
Composition varies
Continental Versus Oceanic Crust

Continental






Granite
Low density
Light
Thick (20 – 50 km)
Can be old (3.8by)
Note: Density = Mass
Volume

Oceanic





Basalt
High density
Dark
Thin (5 km)
Young (<200my)
The Lithosphere
Lithosphere = Outer layer of mantle + Crust
The pates
involved in
plate tectonic
motion are
plates of the
lithosphere
Plates of the Lithosphere
Principles of Plate Tectonics
 The
plates of the lithosphere carry the
continents like passive passengers

Pangaea
• 200 million years ago all the continents were
combined into one landmass
Pangaea
The average rate of plate movement today is between
2 and 12 centimeters (1 an 5 inches) per year
East Pacific Rise
Mid-Atlantic
Ridge
Plate Tectonics
Subduction Zones and Trenches
Oceanic Plate: Label
Continental Plate: Label
Collision Between Two Oceanic Plates
Island arc at trench
Volcano rising from hotspot
Divergent
__________
Boundary
Examples?
Divergent Boundaries
Convergent
__________
Boundary
Trenches and volcanoes are associated with this type
of boundary
Oceanic – Continental Convergence
Peru – Chili Trench
Andes Mountains
Transform Boundaries
The San Andreas Fault occurs at a transform boundary
Evidence For Plate Tectonics
 Fit
of continents
 Matching sequences of rocks
 Fossils
 Mid-Ocean Ridges


Sediment gets (thicker/thinner?) as you
move away from crest of mid-ocean ridge
Rocks get (older/younger?) as you move
away form the ridges
Fit, Rocks, and Fossils
Mesosaurus Fossils Link
Africa and South America
Geological Provinces of the
Ocean
Continental Margins
Continental Shelf






Gently sloping
Exposed during times
of low sea level
Biologically richest part
of ocean
8% of ocean surface
area
Submarine canyons
Ends as shelf break
The Continental Shelf Off Of Los Angeles
Continental Slope

Steep
 Edge of continent
 Along active margins
the slope descends
into submarine
canyons
Continental Rise

Sediment deposits on
ocean floor
 Found on passive
margins (not active
margins)
The Continental Shelf Off Of Los Angeles
Active Versus Passive Margins
Active
• Trenches
• Narrow shelves
• Rocky shorelines
Passive
• Flat coastal plains
• Wide shelves
• Trailing edge of
continent
Mid-Ocean Ridges
Seamounts = Submarine Volcanoes
Tablemount = Flat Topped Seamount
Plankton
Arrow worm
Copepod
Cyanobacteria (P/S)
10% Efficient
Fish
Arrow Worms
The Sun
10% Efficient
10% Efficient
1-2%
Efficient
Copepods
Herbivorous
zooplankton
Diatoms and Dinoflagellates
10% Efficient
Plankton versus Nekton

Plankton


Weak swimmers
Ride the ocean
currents

Nekton


Strong swimmers
Can swim against the
currents
Phytoplankton versus Zooplankton

Photosynthetic (P/S)

Nonphotosynthetic
(non-P/S)

Autotrophic

Heterotrophic

Diatoms and
Dinoflagellates
Copepods
Brown Pelican
10% Efficient
Large Carnivorous Fishes
The Sun
1-2%
Efficient
Small carnivorous fishes
Herbivorous Zooplankton
10% Efficient
10% Efficient
10% Efficient