Plate Tectonics and Earthquakes

Normal Fault

cracks where tension causes one block of rock (hanging wall) is sliding downward and away from another rock (foot wall)

Reverse Fault

compression causes one rock (hanging wall) to move up relative to the other rock (foot wall)

Divergent Boundary

plates move apart (diverge)

Convergent Boundary

plates come together (converge)

Strike Slip Boundary

two plates grind together and slip past one another horizontally

Faulting

A break in the Earth's crust

Seismograph

An instrument that detects and measures seismic waves

Richter Scale

An open-ended theoretical scale used to measure the magnitude of earthquakes

Mercalli Scale

Measures earthquakes intensity. Describes damage to structures. Ranges from I (felt by only a few) to XII (total destruction).

Plasticity

The property of a solid with the ability to flow like a liquid at very, very slow rates.

Focus

The point below Earth's surface where rocks break and move.

Epicenter

The point above Earth's surface directly above the focus.

Primary Waves (P waves)

The fastest traveling Seismic Wave, travels through solids, liquids and gases.

Secondary Waves (S waves)

slower than Primary Waves, travel through solids, but not liquids and gases

Surface Waves (L waves)

The slowest moving Seismic Wave.

Pangaea

means "all Earth"

Earthquake

The shaking and trembling resulting from movements of Earth's crust or plate tectonics.

Sea Floor Spreading

The process by which plate tectonics produces new oceanic lithosphere at ocean ridges.

Continental Drift

A hypothesis that originally proposed that the continents had once been joined to form a single super continent; The super continent broke into pieces, which drifted into their present-day positions.

Plate Tectonics

The theory that proposes that Earth's outer crust shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself.

Panthalassa

The huge ocean surrounding Pangaea.