basalt: An igneous rock rich in iron and magnesium. The bulk composition of the ocean crust is basaltic.
conduction: Transmission of heat between adjacent molecules. Contrasts with convection.
convection: Transmission of heat by movement of mass. Contrasts with conduction.
Coriolis force: A force imparted by the rotation of a body.
fossil homology: The occurrence of identical fossils or assemblages of fossils in distant areas.
granite: An igneous rock rich in silicon and aluminum. The bulk composition of the continental crust is granitic.
isostasy: Principle linking the stability and elevation of the Earth's crust to its density and thickness.
isotope: An atom with a certain number of protons and neutrons. Different isotopes of a given element have the same number of protons but different numbers of neutrons. Radiogenic isotopes are unstable and undergo radioactive decay, releasing energy and producing new, daughter isotopes. Stable isotopes do not decay.
Permian: The geologic period spanning 300 to 250 million years ago.
plasticity: Property of a material that permits permanent deformation without fracture.
plumb bob: A weight attached to a string used to define a vertical line. A surveying tool.
remanent magnetism: The alignment of magnetic minerals in response to a magnetic field. This alignment is locked in when the rock cools below a certain temperature and can be used to determine the polarity of the Earth's magnetic field and the location of continents in the recent geological past.
thrust sheets: A continuous tract of crust forced atop adjacent, usually younger rocks during compression.