Plate Tectonics

Continental drift• – Wegner’s idea that states continents have

moved horizontally along Earth’s surface to their present positions

The drawbacks to continental drift

Pangaea – one supercontinent

Plates are Plates are constantly constantly movingmoving

Plate Boundary Features

Evidence that supports Continental Drift

1. Continents fit together like puzzle pieces.

Going Back in Time!!! 230 mya

Evidence that supports Continental Drift

2. Matching rock layers that were found on Africa and South America.

Evidence that supports Continental Drift

3. Matching fossils of land-based dinosaurs such as Mesosaurus in the southern region of both Africa and South America.

Evidence that supports Continental Drift

4. Ancient Climates – Evidence of ice sheets on continents.• Tropical plant fossils found in the rocks of Antarctica.

Evidence that supports Continental Drift (seafloor spreading) Harry Hess

5. Polarity of ocean crust• Earth’s poles reverse over and over so the iron in the basaltic ocean crust points in different directions.

• (look at animation!!!!)

PPaalleeoommaaggnniittiissmm

20km 20km

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0803/es0803page01.cfm?chapter_no=visualization

Seafloor Spreading and Magnetization

Glomar Challenger

Evidence that supports Continental Drift (seafloor spreading)

Age of ocean rockThe Glomar

Challenger was a drilling ship that found that the youngest ocean rock is near the rift zones and gets older the further away you get from them.

Red – Young Yellow – Average Blue - Old

Convergent Boundaries – Coming together

Subduction – trenches form

Convergent

Divergent

Subduction

Asthenosphere underneath

Divergent Plate Boundary

Mid-Ocean RidgeRift Valley

Young OceanFloor

Old Ocean Floor Old Ocean Floor

Divergent Boundary

• Place on the Earth’s crust where the plates are moving away from each other.

Rift Valley

Mid-Oceanic Ridges

*Tension Forces

New Ocean Floor Creation

Two plates moving against one another

Strike-Slip (Transform)

Transform Fault / Strike Slip (Shearing force)

San Andreas fault (California) Transform Fault/Strike-Slip Boundary

Two Continental Plates

Continental Plates Collide

Continental Plates

Form Mountains (Himalayas, Ural)

Convergent Margins: India-Asia Collision I

Convergent Boundary• Occur in areas where two tectonic plates are colliding

into one another.

Continental Plate

Continental Plate

Oceanic Plate

Subduction

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

Continental-Continental Convergence

• Two low density granitic plates colliding creates mountains like the Himalayas (Mt. Everest)

Oceanic-Continental Convergent Boundaries (Subduction)

Oceanic plate in water

ContinentOceanic Crust

WET

Subduction!!!!!

Magma Chamber

Oceanic-Continental Convergence

• Pressure eventually melts the oceanic plate creating less dense magma that comes to the surface through continental volcanic arcs (Andes).

More dense oceanic plate

Less dense continental plate

Subduction Zone!!!!

Yummy!

ANDESANDES

Oceanic-Oceanic Convergent• Volcanoes form on the ocean floor

creating volcanic islands arcs. (Philippines, Japan)

Hotspots (like Hawaii)

• The Hawaiian Islands were formed as the Pacific Plate moved in a Northwesterly direction over a hot spot. The hot spot never moves. Magma spurts out of the hot spot creating a volcanic island chain.

Seamounts

Quiz – Part 1Indicate divergent, convergent, transform

Quiz!!!!!

1. What is the name of the ancient super continent.

2. Who proposed the theory of Continental Drift?

3. Name three pieces of evidence that support continental drift.

4. Draw a convergent Oceanic-Continental boundary. Label all features.

5. Name a famous transform fault.