Focus- Plate Tectonics

Ch 10

FOCUS: CONTINENTAL DRIFTSec 1

Where is one of the coldest places on earth?

Antartica!

How cold do you think it is there?

0- -90 degrees Celcius!!!!

What kind of life would you expect to find there?

What has been found there…

Do you know what this is?

Hadrosaur!

= Big Lizard!

This guy was found in Antartica!!! How is this possible?

Pangaea

400 mya all the continents were joined together in a big supercontinent!

Antarctica was a lot warmer back then.

What happened to Pangaea? The continents separated!

What is that process called?

Continental Drift

How does that work?

Convection currents under earth’s crust push the plates together and tear them apart.

The man:AlfredWegner

Observed similar fossils on separate continents and thus formulated the theory of Continental Drift

What happened after Pangaea

200 mya Pangaea broke up.

70 mya Antarctica moved to its present position.

Take a moment and answer the questions on page 2

Focus Sec. 2

Seafloor Spreading

Have you ever walked into an ocean or lake? What did the bottom feel like?

Major Fault lines

Where do most of these faults occur?

Deep Sea Vent What are they?

- they are a geyser on the seafloor.

How do they form?

- Areas along the ocean ridges, where the tectonic plates are moving apart.- This creates cracks in the ocean floor then water seeps into these openings -heated by the molten rock or magma. - the water is heated it rises back in to the ocean through the seafloor opening.

Harry Hess 1960 suggested an

explanation to continental drift.

Seafloor spreading-As seafloor spreads basaltic magma flows up

-becoming solid as it cools forming new seafloor

-the new seafloor moves away form the mid ocean ridge -as it cools more making it denser and sinking helping form the ridge

Plates

Convection currents are the circular motion in a liquid caused by heating and cooling.Convection current is the flow of hot fluid in a circular pattern.

MAGNETIC FIELD World War II they used a

magnetometers-- this instrument could be used to measure the strength and direction of a magnetic field.-used to help detect the steel-hulled submarines-this was when they found that the seafloor had a pattern of magnetic variation-alternating bands of rocks recording normal and reverse polarity, arrange systematically around the mid-ocean ridges.

Support Seafloor Spreading

-Magnetic field normal polarity, sometimes it reverses-The north magnetic poles becomes the south and vice versa-Basaltic lava contains iron bearing minerals, magnetite-Provided evidence for seafloor spreading.

Take a moment and answer the questions on page 6

Focus Sec. 3

Plate Tectonics

EruptionPlate boundaries is where the action

happens. What type of plate boundary resulted in

the eruption of the 1912?

Rigid Plates

When the plates move they carry the continent and ocean floors with them.

Plate Boundaries- Divergent- 2 Types

When the lithosphere pulls away from each other

Ocean ridgesRifts

Plate Boundaries- Convergent- 3 Types These are known as Subduction Zones

Plate Boundaries- Transform Fault-

Plates move horizontally relative to each other.

the North American Plate and Pacific Plate

Density of the plates

Ocean Crust Iron rich rock

Basalt Density 3.0 g/mL

Continental Crust Silica rich rock

Granite Denisty 2.7 g/mL.

Examples of Plate Boundary Movement

Plate Boundary Movement Example Locations

1. Collisional (or Convergent)  

    • Continental-Continental Himalayan Mountains (Mt. Everest)—India/Nepal/Pakistan

    • Oceanic-Continental Andes Mountains , Cascade Mountains

    • Oceanic-Oceanic Caribbean Islands, Japan

2. Transform Boundaries (plates slide past each other)

San Andreas Fault , Denali Fault ( Alaska )

3. Divergent (spreading ridge, or sea floor spreading)

Iceland , Baja California , Red Sea

Take a moment and answer the questions on page 13