Download Plate Tectonics

Bringing It All Together!
In the 1960s a third and final theory was proposed.
Plate Tectonics
Plate Boundaries
Unit Essential Question:
How does the Earth recycle and renew its surface?
Presentation Objectives:
§ Define the theory of plate tectonics.
§ Explain how the Earth is divided into layers based on chemical and physical properties.
§ Define the asthenosphere and lithosphere.
§ Describe the plate motion at each of the three different plate boundaries.
§ Describe the features associated with each type of plate boundary.
§ Review density and use it to determine which plate will sink at a convergent boundary.
§ Explain how Earth’s surface is recycled.
Layers of the Earth
• This theory is a combination of...
• The Theory of Continental Drift which states that ...
...the Earth’s continents were once together in one single
landmass, and have since drifted to their present position
when this super continent broke apart.
• The Theory of Sea Floor Spreading which states that...
...new ocean crust is formed at mid ocean ridges where
magma rises to the surface and destroyed at deep sea
trenches.
• The Theory of Plate Tectonics states that...
...the surface of the Earth is broken into large plates, the size and
position of which is changing over time.
The Plates of Plate Tectonics
The Lithosphere is made of the crust and the rigid upper mantle.
The Asthenosphere is made of the soft upper mantle.
The lithosphere is broken into enormous pieces that we call plates.
Tectonic plates move in different directions and at different rates!
Plates interact at plate boundaries, creating characteristic features and processes.
Divergent Plate Boundaries
• At divergent plate boundaries, the plates are moving AWAY
from each other.
Divergent Plate Boundary: Ocean-Ocean
Rift
Mid-ocean Ridge
New ocean crust is created, which means the ocean is expanding!
Divergent Plate Boundaries
• At divergent plate boundaries, the plates are moving AWAY
from each other.
Divergent Plate Boundary: Continent-Continent
Rift Valley
Continental Rift
Since basalt crust is formed here, a new ocean is forming!
Subduction
Convergent Boundary: Ocean-Ocean
Deep Sea
Trench
Plate 2
1
ate
Pl
x
•
•
•
Older is colder is denser…Older plates subduct.
Basalt is denser…Oceanic plates subduct.
•
Trench
Plate 1 subducts under Plate 2.
Plate 1 is denser than Plate 2.
Plate 1 is Older plate is more dense so it subducts under the younger plate.
Features:
•
•
•
Convergent Boundary: Ocean-Continent
Near the Boundary!
Volcanic Island Arc
Deep Sea trench
Earthquakes
Convergent Boundary: Continent-Continent
Plate 1
x
Asthenosphere
Asthenosphere
Plate 1 subducts under Plate 2.
Plate 1 is denser than Plate 2.
Plate 1 is an oceanic plate so it subducts under the continental plate.
• Features:
•
Volcanic Mountains
•
Trench
•
Earthquakes
Plate 2
Plate 2
1
ate
Pl
•
•
•
Asthenosphere
• Features:
• Mountains
At the Boundary!
• Earthquakes
Near the Boundary!
Recycling!
Transform Boundary
• At transform plate boundaries, the plates slide past each other.
A
B
A
• New oceanic crust is created at B, which is a divergent
boundary.
• The old oceanic crust is subducted and destroyed at A
which is a convergent boundary.
Created at the same rate as it is destroyed so Earth remains the same size!
• Features:
• Fault
• Earthquakes
• Tsunamis
Fault