Transcript HISTORY OF THE OCEANS

HISTORY OF THE OCEANS
Earth
• Formed about 4.5 billion years ago
• The sea floor is locked in a perpetual
cycle of birth and destruction that
shapes the ocean and controls much
of the geology and geological history
of the continent
Geological Processes
• These processes that occur
beneath the waters of the sea affect
marine life and dry land.
• The processes that mold ocean
basins occur slowly over tens and
hundreds of millions of years
• Solid rocks flow like liquid, entire
continents move across the face of
the earth and mountains grow from
flat plains
Geology
• Very important to marine biology
• Habitats are directly shaped by
geology.
• The form of coastlines
• The depth of water
• The bottom surface – muddy,
sandy, rocky
• The geologic history of marine life
OCEANS
Earth – Water Planet
• Oceans cover 71% of the Earth’s Surface.
• 2/3rds of the earth’s land area is found in
the Northern Hemisphere which is only
61% ocean.
• About 80% of the Southern Hemisphere is
ocean.
• Oceans play a crucial role in regulating
our climate and atmosphere.
• Without water, life would be impossible.
The Ocean
• Traditionally classified into 4 large
basins.
• Pacific – deepest and largest, almost
as large as all others combined.
• Atlantic – little larger than Indian
• Indian – similar average depth to
Atlantic
• Arctic – smallest and shallowest
• The oceans cover 70.8 percent of planet Earth.
• By far the largest of the four oceans, the Pacific Ocean covers
nearly one-third of the globe.
• All the continents could be placed into the Pacific Ocean, and there
would still be room left over.
• Average depth is 13,000 feet.
• The hourglass shaped Atlantic Ocean covers approximately 20
percent of the Earth's surface and is the second largest of the 4 oceans.
• It extends from the North Pole southward for 10,000 miles to the
Antarctic continent.
• Average depth of the Atlantic Ocean is 12,000 feet.
• The greatest depth is 28,374 feet, the Puerto Rico Trench.
• The Indian Ocean stretches southward from India to Antarctica.
• It is triangular and bordered by Africa, Asia, Antarctica, and,
Australia.
• The average depth of the Indian Ocean is about 12,750 feet.
• The deepest part is 24,440 feet in the Java Trench.
• The Indian Ocean, like the Atlantic Ocean is divided by a midocean ridge that separates the basin into nearly equal portions.
• Centered approximately on the North Pole, the
ARCTIC Ocean is the smallest of the world's
ARCTIC OCEAN
• Maximum depth is 18,050 feet.
• The Arctic Ocean is divided into two nearly equal
basins: The Eurasia basin & the Amerasia basin.
ARCTIC OCEAN
• The Arctic Ocean is surrounded by landmasses of
Eurasia, North America, and Greenland, and is unlike
the other three oceans because of the perennial ice
Seas
• Connected or marginal to the ocean
basins are various shallow seas:
– Mediterranean Sea
– Gulf of Mexico
– South China Sea
Oceanic Crustal Rocks
• Make up the sea floor
• Consists of minerals called
basalt and have a dark color
• Denser than continental crust
thus lies below sea level and is
covered by water
• Only 200 million years old;
continental crust can be as old
as 3.8 billion years
Mid-Oceanic Ridge System
• 40,000 mile continuous chain of volcanic
submarine mountains and valleys
• Encircle the globe like the seams of a
baseball
• Largest geological feature on the planet
• At regular intervals the ridge is displaced
to one side or the other by cracks in the
earth’s crust called transform faults.
• The Mid-Atlantic Ridge divides the sea floor nearly through the
center and stretches from the polar regions of the North to Antarctica
in the South.
• The Mid Atlantic Ridge was created by the splitting apart of the
super continent of Pangaea 190 million years ago.
Mid-Oceanic Ridge System
• Occasionally the submarine mountains of the
ridge rise so high they break the surface to form
islands such as:
– Iceland and the Azores
• Mid-Atlantic Ridge- runs right down middle of
Atlantic Ocean
• East Pacific Rise – main section in the eastern
Pacific
• Deep trenches are also common in the Pacific –
deep depression in the sea floor
• Earthquakes are clustered at the
ridges
• Volcanos are especially common
near trenches
• Rocks farther from the ridge crest
are older
Plate Tectonics
• Earth’s surface is broken up into a
number of plates.
• These plates, composed of crust
and mantle make up the
lithosphere.
• Plates are about 100km thick
• As new lithosphere is created, old
lithosphere is destroyed elsewhere
• Lithosphere is destroyed at the
trenches.
• A trench is formed when two plates
collide and one plate dips below
the other and slides back down the
mantle.
• Downward movement is called
subduction. Subduction produces
earthquakes and volcanoes, also
underwater.
Earth’s Surface
• Continents have been carried long
distances by the moving sea floor.
• Ocean basins have changed in size and
shape.
• New oceans have been born.
• The continents were once united in a
single supercontinent called Pangaea
that began to break up about 180
million years ago.
Seawater
• Solids dissolved in seawater come from two
main sources
– Some are produced by the chemical
weathering of rocks on land and are
carried to sea by rivers.
– Other materials come from the earth’s
interior. Most of these are release into the
ocean at hydrothermal vents.
Seawater
SEAWATER
• Only 6 ions compose 98% of solids in
seawater
• Sodium and chloride account for about
85% of the solids, why it tastes like
table salt.
• Salinity of the water strongly affects the
organisms that live in it.
• Most marine organisms will die in
freshwater. Even slight changes in
salinity will harm some organisms.