Describe the general theory of Plate Tectonics

 The most famous version of the Theory of Continental Drift was proposed in 1912 by: Alfred Wegener

Alfred Wegener thought whole sections of the crust moved.

Earth surface broken into plates 

Rigid lithosphere plates floating on plastic asthenosphere.

Plates include continent and oceanic parts

 Describe the evidence for plate tectonics

1. The Earths North and South pole have flipped many times

These leaves magnetic ‘stripes’ in  rock containing iron minerals

2. Continents fit like a jigsaw puzzle. Continents used to be together

Matching Mountain Ranges

3. Rocks & Fossils: Fossils match between Africa & S. America

Mountains match between Europe & N. America

PLATE BOUNDARIES: Three types:

Divergent , Convergent , Transform

Divergent: Plates moving apart. Convection cell rising under continent

Why is the Atlantic still getting wider?

The plates are pulled apart by convection currents in the mantle below. Caused by heat released from natural radioactive processes.

Characteristics: Volcanoes: Gentle (basalt).

Mostly under ocean or in rift zones.

Earthquakes are shallow

Convergent: Plates moving towards each other. Three types:

1. Oceanic under oceanic: Trench & volcanic island arc.

2. Oceanic under continent: Trench & volcanic arc on continent.

3. Continental collision.

Mariana’s Trench: The deepest point on earth. On the west coast, in the Pacific Ocean .

Describe the processes happening at subduction zones. (Convergent zones) Oceanic crust destroyed at trenches. One plate sinks under another plate.

Characteristics: Trench. Volcanoes are violent and catastrophic (andesite) Partial melting of oceanic crust.

Earthquakes: deeper as you go away from trench towards continent or island arc

 Describe the processes happening at continental collisions

Subduction zone with continent approaching. Oceanic crust all subducted

Continents collide. Giant folded & faulted mountains.

Earth’s highest mountain range, the Himalayas , was formed when the Indo-Australian Plate crashed into the Eurasian Plate.

Transform Fault: Sliding past each other boundary

These areas are likely to have a rift valley, earthquake, and volcanic action.

For example: The San Andreas Fault lies on the boundary between two tectonic plates, the north American Plate and the Pacific Plate.  The two plates are sliding past each other at a rate of 5 to 6 centimeters each year. This fault frequently plagues California with Earthquakes.

Questions:

The ocean floor becomes increasingly ______ as you travel away from the Mid Atlantic Ridge.  (a) Older, (b) younger.

Where the African plate and the South American plate meet is:
(a) Diverging boundary, (b) Converging boundary,
(c) Sliding past each other boundary. 

Where the Nazca plate and the South American plate meet is a:
(a) Converging boundary, (b) Diverging boundary,
(c) Sliding past each other boundary.

Where the Pacific plate and the North American plate meet is:
(a) Converging boundary, (b) Diverging boundary,
      (c) Sliding past each other boundary.

How do plates move where convection currents are rising:
(a) together, (b) apart.

Spreading centers tend to have________ elevations than the ocean floor near them, because of the heat in the rock.   (a)Higher, (b)Lower.

The deepest places in the ocean occur at deep sea trenches. These are formed at:(a) Subduction boundaries,
(b) Diverging boundaries,    (c) Sliding boundaries.

What percent of all earthquakes occur on the ring of fire?   90%

The North magnetic pole became the South magnetic pole and reversed back again how many times within the past 4 million years? 4

MAGNETIC FIELD region within which a moving charge experiences a force.