Earth's Layers, Continental Drift and Plate Boundaries

Plate Tectonics

Theory that the earth's surface (lithosphere) is broken into huge moving plates that move

Convection Current

when the hot, soft rock on the asthenosphere rises, cools and then sinks in a continuous motion

Continental Drift

Alfred Wegener's hypothesis that continents were joined together and have broken and drifted apart

Rift Valley

place where molten rock rises to the Earth's surface creating new crust

Plate Boundary

location where the edges of two plates meet

Mid Ocean Ridges

huge underwater mountain ranges

Hot Spot

place where the mantle rises to the surface, often in the middle of plates, forming volcanoes

subduction

when two plates collide and one is pushed below the other

Divergent Boundary

boundary where two plates move apart

Convergent Boundary

boundary where two plates push together

Transform Boundary

boundary where two plates scrape together

Fossil Evidence of Continental Drift

fossils of an ancient reptile were found in South America and Western Africa

Climate Evidence of Continental Drift

Fossils of tropical plants found on the shores of Greenland which is now in the Arctic Circle

Geology Evidence of Continental Drift

Rock found in Brazil matches rock in west Africa, and stone in the Appalachian Mountains are exactly like those in Scotland's Highlands

matter

Anything that has mass and occupies space

mass

Amount of matter in an object

volume

Amount of space occupied by an object

density

Mass / Volume

crust

The layer of rock that forms Earth's outer surface

mantle

The layer of hot, solid material between Earth's crust and core.

inner core

A dense sphere of solid iron and nickel at the center of Earth

outer core

A layer of molten iron and nickel that surrounds the inner core of Earth

lithosphere

The rigid outer part of the earth, consisting of the crust and upper mantle.

asthenosphere

The soft layer of the mantle on which the lithosphere floats.

tectonic plates

An irregular section of the lithosphere that floats on the earth's mantle

Pangaea

A supercontinent containing all of Earth's land that existed about 225 million years ago.