Ch. 4 - Earth Science

hot spot

the point where the plum reaches the surface

Lithosphere

A rigid layer made up of the uppermost part of the mantle and the crust.

Theory of Plate Tectonics

The theory that pieces of Earth's outer layer are in constant motion

subduction zones

places where plates are pushed down into the upper mantle

decompression melting

melting due to a drop in confining pressure that occurs as rock rises

ultraslow spreading rates

less than 1cm/0.4 in per year

slow rates

1-2cm/0.4-0.8 in per year

rapid rates

15cm/6in per year

divergent plate boundaries

Areas where plates move away from each other, forming either mid oceanic ridges or rift valleys.

transform plate boundaries

Areas where two plates grind past each other resulting in faults such as the San Andreas Fault. Earthquakes often occur at fault lines.

contracting Earth Model

The model proposing that Earth is cooling and shrinking, which causes the crust to crack and wrinkle, forming land features.

Continental Drift Theory

the idea that continents slowly shift their positions due to movement of the tectonic plates on which they ride

convergent boundary

A plate boundary where two plates move toward each other.