SEAFLOOR SPREADING &
STRUCTURE AND
EVOLUTION OF OCEAN
BASINS
LEARN ABOUT:
Evidences to Explain the Seafloor Spreading
Structure of Ocean Basins
Evolution of Ocean Basins
........
SEAFLOOR
SPREADING
• Geologic process in which tectonic plates or large
slabs of the Earth's lithosphere are splitting apart
form each other.
• The crust and part of the upper mantle are under
tension at a spreading center
• The oceanic crust is pulled apart, allowing magma
to rise to the surface.
• The whole oceanic crust is part of a conveyor belt
system.
FIVE EVIDENCES TO EXPLAIN
SEAFLOOR SPREADING
1. The Ocean Floor
2. Mid-ocean Ridge
3. Deep Sea Trench
4. Geomagnetic Reversals
5. The Age of the Seafloor
THE OCEAN FLOOR
As two tectonic plates slowly separates,
molten material rises up from within the
mantle to fill the opening.
Rugged volcanic landscape of a mid-ocean
ridge is created along the way.
MID-OCEAN RIDGE
Part of chain of mountains 84,000 km long
largest topographic features on the surface of
the Earth.
Spreading center; where the upwelling of
magma from the mantle creates new ocean
floor.
DEEP SEA TRENCH
Long, narrow basins
8 - 11 km below sea level
Formed by subduction
Causes the seafloor and outermost crust to
bend V shaped depression
GEOMAGNETIC REVERSALS
Scientists used magnetometers to study the
ocean floor.
Basaltic magma - “tape recorder”.
The discovery of magnetic stripes provided
powerful evidence that seafloor spreading
occurs.
THE AGE OF THE SEAFLOOR
Scientists noticed that from the ridge crest,
sediment becomes older and the seafloor
becomes thicker.
OCEAN BASIN
5 Major Ocean Basins
Pacific Basin
Atlantic Basin
Indian Basin
Arctic Basin
Southern Basin
Arctic Ocean
EUROPE
NORTH
AMERICA
Pacific
Ocean
Atlantic
Ocean
ASIA
Pacific
Ocean
AFRICA
SOUTH
AMERICA
Indian
Ocean
Southern Ocean
ANTARCTICA
AUSTRALIA
OCEAN
BASIN
In hydrology, an ocean basin is
anything on Earth that is covered by
seawater.
Are a consequence of plate motion.
Subducting slabs pull on their plates
leading to spreading at divergent plate
boundaries.
Are partially bounded by continents.
Interconnected - “World Ocean”
Largest depressions on Earth
STRUCTURE
OF OCEAN
BASINS
Each canyon’s thick fan-shaped
sedimentary deposit is called “abyssal fans”
The ocean floor is found at the base of the
continental rise in water 4,000 - 6,000
meters deep
Scientists estimate that there are
approximately 10,000 volcanoes on the
ocean floor.
STRUCTURES OF
OCEAN BASINS
mid-Ocean ridges
Above the ocean floor
At the center of the ocean’s basins
23% of the earth’s surface
Long linear mountain chain in all oceans
and bound basins
Fracture zones are perpendicular to ridges.
Deep ocean basins
Greater than 4,000m in water depth, typically
flat or subdued topography
Regularly cut by long fracture zones
ocean trenches
Mark the transition between continents and
ocean basins
ocean rises
seamounts - guyots, atolls, all forms of
submarine volcanoes, submarine plateous
EVOLUTION
OF OCEAN
BASINS
Over millions of years, ocean basins open
and close, continents move and change
shape, and mountains are pushed up and
eroded away. Such dynamic processes
continually reshape the surface of the Earth.
The movement of rigid plates on the Earth’s
surface, known as plate tectonics, is the
cause of these changes.
All ocean basins are formed from plate
tectonic activity, weathering and erosion.
Seafloor spreading and subduction are the
primary forms of plate tectonic activity that
provide a pathway for molten rocks to leave
the earth’s mantle and create new oceanic
crust.
WILSON CYCLE
STAGES OF OCEAN
BASIN EVOLUTION
Embryonic
- Continental rifting plays a key role
in the formation of an ocean.
- New basin will become part of the
eventual continentual shelf-slope
rise zone.
Juvenile
- Seafloor basalts begin forming
- Fairly shallow
- Normal marine sedimentation of
muds, sands and limestones,
depending on local condition.
WILSON CYCLE
STAGES OF OCEAN
BASIN EVOLUTION
Mature
- Broad as it widens
- Fairly shallow
- Trenches develop and subduction
begins
- Abyssal plains form
- Fully develop shelf-slope-rise zone
Diclining
- Subduction eliminates much of
seafloor and oceanic ridge
- Dominant motions are spreading
and shrinking
WILSON CYCLE
STAGES OF OCEAN
BASIN EVOLUTION
Terminal
- The continents are not yet
touching but subduction of the
intervening oceanic crust causes a
narrowing of the sea separating the
continents
- African Plate is being consumed
under the European Plate.
Relic Star
- Shrinking and uplifting of young
mountains
SUMMARY
The Structure of Ocean
Basins and The Stages of
their Evolution gives us
the idea that ocean
basins make up more
than 70% of the total land
on Earth.
Arctic Ocean
EUROPE
NORTH
AMERICA
Pacific
Ocean
Atlantic
Ocean
ASIA
Pacific
Ocean
AFRICA
SOUTH
AMERICA
Indian
Ocean
Southern Ocean
ANTARCTICA
AUSTRALIA
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