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Grade 9 Plate Tectonics


Jada Lewis

on 21 May 2015

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Transcript of Grade 9 Plate Tectonics

Plate Tectonics and
The Ring of Fire

(made of the Earth’s outer layer,
The Lithosphere)

The African Plate
2. The North American Plate
3. The South American Plate
The Eurasia Plate
5. The Australian Plate
6. The Antarctic Plate
The Pacific Plate

*there are also several minor plates

•Early explorers notice that some coastlines could fit together like a puzzle

•Fossils of similar species are found on continents separated by large distances

Alfred Wegener
proposes “Continental Drift Theory”, which was initially disproven because no one could figure out the mechanics of Plate Tectonics, which later proved it to be TRUE

•1960’s/1970’s, new information about:
-the ocean floor -Earth's ancient magnetism-heat from Earth's interior
-the distribution of volcanoes, earthquakes, and fossils

The Plate Tectonics theory
is formulated
History of the Science
-also called “T
he Pacific Ring of Fire

- an arc stretching from New Zealand, along the
Eastern side of Asia, north across the Aleutian Islands of Alaska, and south along the coast of North and South America.

-composed of over
% of the world's volcanoes
(both active and dormant)

- the Pacific Plate is colliding with/sliding underneath other plates

-noticed/described before Plate Tectonics theory

-The plates are moving in different directions and at different speeds (from 2 -10cm/year)
-Where the plates meet are called Plate Boundaries, there are 3 kinds of
Plate Boundaries

The Ring of Fire
•where plates crash/crunch together/ folding occurs

•collisions are very slow and last millions of years

an oceanic plate slides under another plat

The crashing of the Nazca oceanic plate into the west coast of South America

The crash formed the Andes Mountains, the volcanoes along the mountain crest, and the deep trench off the coast in the Pacific Ocean
(pulling apart)
(side sweeping)
The Rio Grande rift, New Mexico

•the brittle lithosphere(surface) breaks along parallel faults

•the block between the faults cracks and drops into the soft, plastic interior (the asthenosphere)

•the sinking block forms a rift valley. Magma seeps upward to fill the cracks forming new crust
•where plates slide past each other

•marked in some places by linear valleys along the boundary where rock has been
ground up
by the sliding

•marked in other places by features like stream beds that have been split in half and the two halves have moved in opposite directions

The San Andreas Fault
Los Angeles will creep towards San Francisco, in 10 million years, the two cities will be side by side

-provides geology with a theory that explains "how the Earth works”

-particularly valuable information in areas with volcanoes/earthquakes
A theory that explains that the Earth's surface is made up of plates
•where plates pull apart

fractures (cracks) in the earth's crust where movement has taken place

single faults: cliffs
double faults: rift valleys

•earthquakes occur along faults, and volcanoes form where the magma reaches the surface
-convection current:
circular movement in a gas or liquid created by uneven heating

-very hot material at the deepest part of the mantle rises, then cools, sinks again & then heats, rises & repeats
Full transcript