Download Plate Tectonic Theory

Plate Tectonic Theory
TXT pg. 106
Chapter 3…section 5
Definitions to know
• Plates: Sections of the lithosphere that are
fitted together along cracks
• Scientific Theory: Well tested concept that
explains observations
Theory
• Pieces of the earth’s lithosphare are in slow,
constant motion, driven by convection
currents in the mantle.
• Explains the formation, movement, and
subduction of Earth’s plates.
HOW DO THEY MOVE???
• Movements in the mantle cause the plate to move
• Gravity pulls one side of the plate down by subduction,
causing the rest of the plate to move forward
• As they move, the collide, pull apart, or grind with
other plates
• This causes the formation of volcanoes, mountain
ranges, and deep ocean trenches
Plate Boundaries
• Extend into the lithosphere
• Faults: (Form along the boundaires)Break in the
earth’s crust where rocks have slipped past each
other
• 3 Kinds:
– Divergent
– Convergent
– Transform
Divergent Boundaries
• Plates move apart (Diverge)
• Most occur on mid ocean ridges
• Can occur on land Causing a Rift valley (deep
valley where the plates slide apart
• Example: Death Valley
Convergent Boundaries
• Where 2 plates come together
• When they converge, they will collide. Density decides
which one gets forced up and which one down….More
dense plate sinks under other past
• Oceanic Crust is more dense than continental crust
• When continental crust collides, neither is more dense,
so mountain ranges form.
Transform Boundary
• 2 plates slide past each other in opposite
directions (Like rubbing your hands together)
• Crust is not created or destroyed here
• Earthquakes happen at transform boundaries
Pangea Proof
• By proving that the earth’s plates are moving,
scientists were able to show that there was
once a pangea and that the continents broke
apart and moved to their current position.
• Pg. 110 shows this in motion and the time
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