Download Plate Tectonics

Plate Tectonics
Plate Tectonics
Why Continents and Ocean Basins Exist
Topics
• Density Structure of Earth
• Isostasy
• Sea-Floor Spreading
• Mechanical Structure of Earth
• Driving Mechanism of Plate
Tectonics
• Lithospheric Plate Interactions
• Plate Tectonics and the Depth
of the sea floor
Topics
• Density Structure of Earth
• Isostasy
• Sea-Floor Spreading
• Mechanical Structure of Earth
• Driving Mechanism of Plate
Tectonics
• Lithospheric Plate Interactions
• Plate Tectonics and the Depth
of the sea floor
Sea-Floor
Spreading
Sea-Floor
Spreading
T h e
F o r m a t i o n o f
o c e a n B a s i n s
t h e
Continental Drift
In 1912, Alfred Wegener
published a book which
stated that continents move
In 1912, Alfred Wegener
published a book which
stated that continents move
The concept is called
continental drift
200 million years ago, all of the world’s major landmass
were joined in the supercontinent of Pangaea
200 million years ago, all of the world’s major landmass
were joined in the supercontinent of Pangaea
Since then, the continents have drifted apart
EVIDENCE
Geological Evidence
Climatological Evidence
Geographical
Evidence
Paleontological Evidence
Problem With Hypothesis
of Continental Drift
Problem With Hypothesis
of Continental Drift
What is the driving mechanism?
Problem With Hypothesis
of Continental Drift
What is the driving mechanism?
What makes the continents move?
Problem With Hypothesis
of Continental Drift
What is the driving mechanism?
What makes the continents move?
Wegener’s suggestions for possible driving mechanisms were
not plausible
Problem With Hypothesis
of Continental Drift
What is the driving mechanism?
What makes the continents move?
Wegener’s suggestions for possible driving mechanisms were
not plausible
And most geologists did not accept continental drift
Questions
What does the deep-sea floor look like?
Is the bottom of the deep ocean a flat,
monotonous muddy plain?
Sonar
Sonar
The development of sonar
enabled oceanographers to
rapidly determine the
bathymetry of the sea floor
Sonar
The development of sonar
enabled oceanographers to
rapidly determine the
bathymetry of the sea floor
Bathymetry - measurement
of water depth
Sonar
The development of sonar
enabled oceanographers to
rapidly determine the
bathymetry of the sea floor
Bathymetry - measurement
of water depth
When oceanographers
conducted sonar surveys of
the Atlantic in 1925, they
discovered the MOR
Mid-Ocean Ridge
Mid-Ocean Ridge
MOR is the largest geological feature on Earth
Mid-Ocean Ridge
MOR is the largest geological feature on Earth
MOR is a long, linear feature
Mid-Ocean Ridge
MOR is the largest geological feature on Earth
MOR is a long, linear feature
Summit of MOR averages 2 km below sea level
Mid-Ocean Ridge
MOR is the largest geological feature on Earth
MOR is a long, linear feature
Summit of MOR averages 2 km below sea level
Summit of the MOR is a volcanic region
MOR forms in all ocean
MOR is 60,000 km long
Deep-Ocean Trenches
Deep-Ocean Trenches
Deep-Ocean Trenches
Trenches are long, linear features
Deep-Ocean Trenches
Trenches are long, linear features
Trenches are the deepest part of the ocean
Deep-Ocean Trenches
Trenches are long, linear features
Trenches are the deepest part of the ocean
As deep as 11 km (11,000 m or 33,000 ft)
Deep-Ocean Trenches
Trenches are long, linear features
Trenches are the deepest part of the ocean
As deep as 11 km (11,000 m or 33,000 ft)
Trenches primarily form near the continents
Most deep-ocean trenches form in the Pacific
Deep-Ocean Trenches
Sea-Floor Spreading
Sea-Floor Spreading
A hypothesis proposed by Harry Hess
Sea-Floor Spreading
A hypothesis proposed by Harry Hess
What if the sea floor moves too?
Sea-Floor Spreading
A hypothesis proposed by Harry Hess
What if the sea floor moves too?
What if the entire crust of Earth is mobile?
Sea-Floor Spreading
A hypothesis proposed by Harry Hess
What if the sea floor moves too?
What if the entire crust of Earth is mobile?
The continents drift and the sea floor spreads
The Hypothesis
The Hypothesis
The sea floor separates at the MOR and spreads away
The Hypothesis
The Hypothesis
Magma erupts from volcanoes at the summit of the MOR
and creates new sea floor
An example of sea-floor spreading - Iceland
Iceland is rifting
Hypothesis
Hypothesis
Trenches form as the sea-floor subducts into
the mantle
The sea floor is destroyed during subduction
Sea-Floor Spreading
Sea-Floor Spreading
1.Hypothesis that the sea floor spreads
Sea-Floor Spreading
1.Hypothesis that the sea floor spreads
2.Sea floor is created at the MOR
Sea-Floor Spreading
1.Hypothesis that the sea floor spreads
2.Sea floor is created at the MOR
3.New sea floor spreads laterally in opposite
directions
Sea-Floor Spreading
1.Hypothesis that the sea floor spreads
2.Sea floor is created at the MOR
3.New sea floor spreads laterally in opposite
directions
4.Trenches form as sea floor subducts
Sea-Floor Spreading
1.Hypothesis that the sea floor spreads
2.Sea floor is created at the MOR
3.New sea floor spreads laterally in opposite
directions
4.Trenches form as sea floor subducts
5.Sea floor is destroy during subduction
Sea-Floor Spreading
Question
Question
How would you test the hypothesis of sea-floor
spreading?
Question
How would you test the hypothesis of sea-floor
spreading?
JOIDES Resolution
Pangaea
Next
Mechanical
Structure of
Earth