the heat transfer in a fluid in which hot fluid rises and cold fluid sinks, setting up a cycle

how much space an object takes up (its volume) in relation to the amount of matter in that object (its mass). Another way to put it is that density is the amount of mass per unit of volume. If an object is heavy and compact, it has a high density.

a break in the earth’s crust either within a plate or between plates

any remains, trace, or imprint of animal or plant life preserved in Earth’s crust

the hard outer layer of Earth made of crust and hard, upper mantle; broken into tectonic plates

molten rock under the surface of Earth

sections of the lithosphere that move on top of the fluid asthenosphere; composed of Earth’s crust and the hard top layer of the mantle

the edge of a tectonic plate where earthquakes, volcanoes, and other tectonic activity takes place because of the motions of the plates

a volcanic area that forms as a tectonic plate moves over a place heated from deep within Earth; the Hawaiian islands are an example

an undersea mountain chain where new ocean floor is produced at a divergent plate boundary.

the boundary between two tectonic plates that are moving away from each other

the process by which new oceanic lithosphere forms as magma rises toward the surface and solidifies

large, ancient landmass that was composed of all the continents joined together

provide evidence of sea floor spreading when they show a pattern of magnetic field reversals

a switch in the direction of Earth's magnetic field so that the magnetic north pole becomes the magnetic south pole and the magnetic south pole becomes the magnetic north pole