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The Theory of Plate Tectonics
• The Earth’s crust is broken up into plates
which move around on top of the mantle
**Driven by convection currents**
Evidence for the Theory of Plate
Tectonics
1. The same fossils found on
distant continents
Evidence for the Theory of Plate
Tectonics
2. Rock Formations across continents match up like a
puzzle
Evidence for the Theory of Plate
Tectonics
3. Glacier debris is found and is similar on
several continents
Evidence for the Theory of Plate
Tectonics
4. Seafloor Spreading
– New oceanic crust is always being made
Evidence for the Theory of Plate
Tectonics
5. Magnetic Striping of the
sea floor
Shows that the Earth’s magnetic
poles have reversed many times
in throughout Earth’s history
Plates moving together
Plates moving apart
Plate Boundaries
• Plate type: DIVERGENT : plates move away
from each other
• Results: Sea floor spreading
• Forms a mid-ocean ridge (underwater
mountain chain)
Plate Boundaries
• Plate type: CONVERGENT: plates move toward
each other
Convergent Boundaries
• Forms regular and volcanic mountain ranges
• Forms deep ocean trenches at subduction zones
Plate Boundaries
• Plate type: TRANSFORM
• Plates that slide past each other
• Results: earthquakes
– http://www.classzone.com/books/earth_sci
ence/terc/content/visualizations/es0804/es
0804page01.cfm?chapter_no=visualization