PLATE TECTONICS

WHY?Alfred Wegener:• Noticed the similarities in the

shoreline of continent on both sides of the Atlantic Ocean, he then began fitting them together.

• Introduced the hypothesis of continental drift.

• Suggested a supercontinent, called Pangaea (meaning "all land"), that broke up millions of years ago, slowly moved to their current positions, and continue to move today.

LITHOSPHERE / ASTHENSPHERE

CONVECTION CURRENTS:-Hot magma from the mantle rises, cools, + sinks.-Mantle moves + drags plates along with it.

PLATES

DIVERGENT• DIVERGENT- When two plates move away from each other.

Characteristics: Mid – ocean ridges (underwater mountain ranges)

Rift Valleys (narrow valleys that form where plates separate), Newest rock material (cooling magma forms new oceanic crust).

DIVERGENTEx: Seafloor Spreading

• CONVERGENT – When two plates collide.

Characteristics: Mountains, most earthquakes, Volcanoes

1.ocean – ocean 2.ocean – continent 3.continent – continent

CONVERGENT

OCEAN – OCEAN CONVERGENT BOUNDARY: Subduction Zone Mantle rock melts + magma rises to the surface, creating islands.

OCEAN – CONTINENT CONVERGENT BOUNDARY: Subduction ZoneOceanic Crust is more dense + sinks under Continental Crust

CONTINENT – CONTINENT CONVERGENT BOUNDARY: Plates collide + the edges crumple,

causing uplift = mountains

TRANSFORM BOUNDARY• TRANSFORM – When two plates are moving past each

other.

Characteristics: San Andreas Boundary

Ex: SAN ANDREAS BOUNDARY The Pacific plate and North American

plate grind past each other side by side.

REVIEW

HOT SPOTS

AREA WITHIN A PLATE WHERE MAGMA WORKS ITSELF TO THE SURFACE ARE CALLED HOT SPOTS.

HOT SPOTS ARE STATIONARY SO WHEN THE PLATE ABOVE IT MOVES A NEW VOLCANOE FORMS.