Plate Tectonics Objective: describe the theory of plate tectonics.

Plate Tectonics

Objective: describe the theory of plate tectonics

Plate TectonicsThe crust is embedded into the lithosphere and broken into plates

Plate TectonicsPlate tectonics: continents are embedded in lithospheric plates, as the lithosphere moves on the asthenosphere, the continents also move.

What makes plates move?

The heat of the mantle forms a process called Convection.

As the magma in the mantle that is close to the core heats up, it rises towards the surface of the Earth.

When it gets near the surface it cools and sinks back down again, gets re-heated and the process repeats

Why do plates move?This movement of magma into the asthenosphere is what causes the lithosphere and plates to move!

Develop a Theory

Come up with a theory to explain the next 3 pieces of evidence…

Evidence #1

The continents look like they fit together.

Evidence #2

Some fossils are only found in isolated parts of the world all the way across the oceans.

Evidence #3Rock layers and structures match in continents separated by the oceans.

What does this evidence support about how the world looked 250 million years ago?

Why/What caused continents to move?

Continental Drift Theory

Continental drift theory is the movement of the continents

It states that 250 million years ago the continents were one super continent and have since drifted apart

The super continent is called Pangaea

The Evidence:

While we cannot go back 250 million years and observe the position of the continents (since we don’t have a time machine), here is the evidence that supports continental drift theory:

Evidence for continental drift

1. The continents appear to fit together

2. Fossils of the same animals and plants are found on different continents

3. Matching rock formations are found on different continents

Stop!

Plate Boundaries

The edge of a plate where it meets another plate is called a Plate Boundary

There are three things that can happen at plate boundaries:

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=08

1: Plates can move apart- Divergent

Animation!

http://scign.jpl.nasa.gov/learn/plate4.htm

Divergent:

This happens at Mid-ocean ridges, it causes the sea to get wider. (Sea-Floor Spreading)

Causes earthquakes, volcanoes, rift valleys, ridges.

Ex: the Mid-Atlantic ridge, the East Pacific Rise

2: Plates can slide past each other- Transform

Transform:

Plates slide past each other

Causes earthquakes

Ex: San Andreas Fault, North Anatolian Fault

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=08

3) Plates move towards each other- Convergent

Three types of convergent boundaries-a) Ocean-ocean subductionb) Ocean-continent subductionc) Continent-continent collision

Subduction means one plate diving under another plate

A: Ocean-ocean subduction

Occurs deep in the ocean.

Causes deep-sea trenches, earthquakes, volcanic island arcs

Ex: Indonesian Islands

A: Ocean-ocean subduction

PICTURE!

B: Ocean-continent subduction

An oceanic plate dives under a continental plate

Causes deep-sea trenches along continents, earthquakes, volcanoes on the edge of a continent

Ex: Western coast of South America

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=08

B: Ocean-continent subduction

Picture!

C: Continent-Continent Collision

Two continents run in to each other.

Causes mountains to rise (mountain building), earthquakes

Ex: Himalayas- India crashed in to Asia!http://www.classzone.com/books/earth_science/terc/content/visualizations/es0808/es0808page01.cfm?chapter_no=08

C: Continent-Continent Collision

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0808/es0808page01.cfm?chapter_no=08

Questions (due Monday!):

Section review 8.2- pg 179

1: Explain how new oceanic crust is formed at a divergent boundary.

2: Describe two different types of subduction boundaries. Use the plate boundary map on pages 712-713 to identify an example of each type.

3: Describe what happens at a collision boundary. Identify a collision boundary on the map on pages 712-713.

4: Describe the movement of plates at a transform boundary, and give some examples.

5: What types of plate boundaries are not shown in the diagram on pages 174-175?

6: Critical Thinking: Explain how the densities of oceanic crust and continental crust influence what happens when an oceanic plate converges with a continental plate.

7: Geography: In 2001, a large earthquake related to the movements of two plates occurred about 20 kilometers northeast of Olympia, Washington. Use the map on pages 712-713 to identify the plates and the type of boundary they share.