Download The Theory of Plate Tectonics Plates

The Theory of
Plate Tectonics
Plates
• Separate sections of Earth’s outer shell, the
lithosphere
• Plates have jagged edges but fit closely together
• Some plates carry the continents or parts of the
ocean floor or both
Scientific Theory
• A well tested concept that explains a wide
range of observations
J. Tuzo Wilson
• Canadian scientist
• Observed cracks in continents similar to
those in ocean floor
The Theory of Plate Tectonics
• The theory of plate tectonics is the
geological theory that states that the
pieces of Earth’s lithosphere are in
constant slow motion being driven by
the convection currents in the mantle.
• The theory of plate tectonics
explains the formation, movement
and subduction of earth’s plates.
• Plate Boundaries - where 2 plates meet,
they extend deep into the lithosphere
• Fault – breaks in Earth’s crust where
rocks have slipped past each other
3 Types of Plate Boundaries
1. Transform
2. Divergent
3. Convergent
Transform Boundary
• Where 2 plates slip past each other
moving in opposite directions
• Earthquakes occur frequently along
transform boundaries
Divergent Boundary
• Where 2 plates move apart or diverge
• Most occur at the mid-ocean ridge
Rift Valley – a deep valley that forms
along a divergent boundary on land
Convergent Boundary
• Where 2 plates come together or collide
• The density of the plate determines which
one comes out on top
Collisions at Convergent
Boundaries and their Results:
• Oceanic crust + Oceanic crust = deep ocean trench
• Continental crust = Continental crust = mountains
• Oceanic crust + Continental crust = deep ocean trench
and mountains
The Continents Slow Dance
• The plates move at a slow, steady pace of
about 1-10 cm/year
• Compare to the rate of fingernail growth
• The rate of plate movement is slow, but
multiply it over millions of years to
understand how Pangaea became Earth’s
continents today.