asthenosphere

-is a semi-plastic layer in the structure of the Earth which is beneath the lithosphere and is variable
in thickness.

atmosphere

-is the outermost spherical structure comprising a planet; the gases that cover the planet.

continental crust

is a portion of the Earth's crust that is thicker and less dense than oceanic crust. Consequently, this
type of crust floats at a higher elevation above the mantle and protrudes above sea level to form
continents.

core

-is the innermost spherical structure of a planet; it is the densest material, probably consisting
mostly of iron and nickel, similar to the composition of iron meteorites. The outer portion is liquid
and the inner portion is solid.
-core-Opal's Pals

crust

-is the upper most solid layer of the earth's structure; often divided into oceanic crust (thinner) and
continental crust (thicker).

density

-is a measurement of the mass of an object compared to its volume; often expressed in terms of
grams per cubic centimeter.

gravitational magmatic segregation

-Under the influence of gravity, crystals that form as as a magma cools either settle to the bottom
of the magma chamber (dense compounds) or rise to the roof of the magma chamber (low density
compounds).

hydrosphere

-is the layer of water that covers the crust of a planet.

isotasy

-is tied into the concept that the crust of the planet floats on top of a denser, semi-plastic mantle. 
Mountain ranges, made mostly of granite, stick up higher than surrounding plains because the
crust beneath the mountains is thicker, allowing the mountains to float higher.

mantle

-is the layer of the Earth located between the lithosphere and the core

mantle plume

-is located where hot, low density molten (or semi-molten) material rises from the mantle and
comes up underneath the crust.

oceanic crust

-is the crust of the Earth beneath the oceans; typically only 2 to three miles thick.

thermal convection

-Within the mantle of a planet, hot fluid material rises because of its lower density, while cold
material sinks because of its higher density