Download Oceans

Oceans
Ancient Oceans
• 250 million years ago there was one super
ocean called Panthalassa
• Ocean landscape often changed by
volcanoes and earth’s movements
Ocean Climate
• When wind blows over the ocean it pushes
water on the surface
– Water changes shape forming waves
– Stronger the wind, bigger the waves
Currents
• Currents are masses of water that are
always on the move
– Ocean currents on the surface caused by wind
and the earth's spinning
– North of the equator in earth's Northern
Hemisphere, circular currents flow in a
clockwise direction
– South of the equator in the earth's Southern
Hemisphere currents move counterclockwise
The Underwater landscape
• Underwater landscape
– Canyons, mountains
and many active
volcanoes
– Picture:underwater
coral canyon
Pacific Ocean's Ring of Fire
• Contains 75% of the
earth's volcanoes
• Reaches from the
waters off New Zealand
and around the
Philippines to Alaska
and down the coast of
North and South
America
Underwater eruptions and
earthquakes rock the
waves.
The Tides
• The alternate rising and falling of the water level
along the shore is called the tide
• High tide is when the water has crept as far up on
the shore as it will go on a given day
• Low tide is when the water retreats leaving an
increasing amount of sand, mud, or rocks exposed
What makes the tide?
• Tides are caused by the sun and moon.
• They exert a gravitational pull on the earth
and because the ocean water is fluid, it
can respond to this pull by moving
towards the sun and moon.
• As the earth turns on its axis whatever
part of the ocean is closest to the moon
bulges towards it, and experiences high
tide.
Oceans Today
• 5 great oceans
– Pacific, Atlantic, Southern, Indian, Artctic
• All around these are smaller areas of
water known as seas
• Oceans and seas form one continuous
body of water
The Pacific Ocean
• Covers almost a third of Earth’s surface
• Has more islands than all of the other
oceans combined
• El Nino:
– Climate pattern that occurs across the tropical
Pacific about every 5 years
– High atmospheric pressure in the Western
Pacific and can cause huge waves
The Atlantic Ocean
• Second largest ocean
• Fewer islands than the other oceans
• Big seas such as the Mediterranean
• Hurricanes/tropical cyclones and other
devastating storms sweep through the
ocean
Indian Ocean
• Mostly warm with many sheltered areas
• Home to many island nations
• About 40% of the world’s offshore oil from
this ocean
• Coral islands:
– Coral animals like the warm calm water
– Huge rocky reefs and islands here
The Southern Ocean
• Not all open water
• In winter great sheets of ice spread out
from the Antarctic continent and float on
the water
• Large pieces of the ice often break off the
sheets and become icebergs
The Arctic Ocean
• Smallest and shallowest of the 5 oceans
• Joins the other oceans through two gaps,
one to the Pacific between Russia and
Alaska and one to the Atlantic between
Greenland and Northern Europe
– Otherwise surrounded by land
Continental and Oceanic Crusts
• The geologic
distinction between
ocean and
continents results
from the physical
and chemical
differences in the
rock that makes up
the crust.
Continental and Oceanic Crusts
• The nature of the
rock determines
the elevation of a
particular area of
the earth's crust
and therefore
whether or not it is
covered by water
Oceanic crust-makes
up the sea floor
Made up of a mineral
called basalt
-dark color
Continental and Oceanic Crusts
• Most continental
rocks are made of
granite
– Different
composition, lighter
color
Oceanic Crust
Denser than
continental crust
Below sea level
Both are less dense
than the underlying
mantle
Floats on the mantle
Continental and Oceanic Crusts
• Continental
– Can be as old as
3.8 billion years old
Oceanic Crust
-thinner than
continental
Less than 200 million
years old