Lesson 1 Earth's Changes Over Time

Front

continental drift

Back

the movement of the Earth's continents relative to each other.

Front

fossil

Back

the preserved remains or traces of ancient organisms.

Front

superposition

Back

a principle that states younger layers of rock are deposited on top of older layers.

Front

plate tectonics

Back

the theory that the Earth's outer shell is divided into several plates that glide over the mantle.

Front

seafloor spreading

Back

the process by which new oceanic crust is formed at mid-ocean ridges.

Front

mid-ocean ridge

Back

an underwater mountain range formed by plate tectonics.

Front

magnetic reversal

Back

the change in the Earth's magnetic field, where the magnetic north and south poles switch places.

Front

asthenosphere

Back

the semi-fluid layer of the mantle on which tectonic plates move.

Front

lithosphere

Back

the rigid outer layer of the Earth, consisting of the crust and upper mantle.