Plate Tectonics

Fossil

Any remains, impression, or trace of a living thing of a former geologic age.

Similar fossils were found on different continents to help prove the theory of Pangea.

Alfred Wegener

The scientist who introduced the concept of continental drift. His idea of Pangaea (the continents were once one big land mass)came from studying the shape of the continents and noticing that they looked like they fit together like puzzle pieces. He also noticed that similar fossils were found on different continents and try to explain that it was because the continents were once one big supercontinent.

Scientists did not believe Wegner's theory and tried to disprove it. Once the seafloor was mapped Wegener's theory was proved.

Continental drift

theory that explained how continents shift position on Earth's surface

Pangea

A supercontinent: the earth's landmass when all the continents were connected.

Harry Hess

He used sonar to map the ocean floor. While looking for submarines during WW11, he discovered many plate boundaries underwater including the Mid-Atlantic Ridge

mid ocean ridges

where magma comes up and is associated with seafloor spreading (where new seafloor is "born")

Mid Atlantic Ridge

an example of a mid ocean ridge (most famous)

found running on the north/south axis of the Atlantic Ocean

10,000 miles in a curving path

seafloor spreading

new molten material from inside the earth erupts, cools and hardens to form a solid strip of rock

the seafloor is getting bigger

deep ocean trench

a deep valley along the ocean floor beneath which ocean crust slowly sinks towards the mantle

destroys seafloor ("death")

Mariana Trench

example of a deep ocean trench

Deepest known part of the world's ocean

In western Pacific Ocean (near Asia)

subduction

Ocean floor sinks beneath a deep-ocean trench and back into the mantle.

Causes convection currents

Convergent plates of different weight collide and the heavier plate pushes under the lighter plate.

seafloor spreading and subduction

together change the shape of the oceans

plate

Section of the lithosphere that slowly moves, carrying piece of contenental and ocean crust

lithosphere

crust and upper mantle

boundary

a place where two tectonic plates meet

divergent boundary

Plates that move away from each other.

creates

seafloor spreading in the ocean

rift valleys on land

convergent boundary

Plates that move towards each other

creates:

mountains (when the plates have the same densities)

subduction zones (when plates have different densities)

transform boundary

Plates slide past each other

creates:

earthquakes

faults

Fault

Break in the Earth's crust where rocks have slipped past each other

Forms along boundaries

Plate Tectonics

Combines sea-floor spreading, Earth's plates, and plate motions into one theory

Rift Valley

When pieces of Earth's crust diverge on land: end up with a deep valley

a long steep valley formed when 2 plates divide and the land between them sinks