Geology Glossary

The weak, ductile, partially molten layer of the upper mantle beneath the lithosphere, upon which tectonic plates float and move.

The tendency of a mineral to break along flat, planar surfaces determined by its internal crystal structure, producing smooth, regularly oriented faces.

A tectonic boundary where two plates move apart from each other, allowing magma to rise and create new lithosphere, as seen at mid-ocean ridges.

A sudden release of energy in Earth's crust that creates seismic waves, typically caused by the movement of faults or volcanic activity.

The process by which rock and soil are removed from one location and transported to another by natural agents such as water, wind, ice, and gravity.

A fracture or zone of fractures in Earth's crust along which there has been displacement of the two sides relative to one another.

Any preserved trace or remains of an organism that lived in the geological past, typically found in sedimentary rock.

The scientific study of landforms and the processes that shape Earth's surface, including erosion, weathering, tectonics, and volcanism.

Rock formed by the cooling and solidification of magma or lava. Intrusive igneous rocks cool slowly underground; extrusive igneous rocks cool quickly at the surface.

The state of gravitational equilibrium between Earth's lithosphere and asthenosphere, such that the crust floats at an elevation determined by its thickness and density.

The rigid outer layer of Earth, comprising the crust and the uppermost part of the mantle, that is broken into tectonic plates.

Molten rock located beneath Earth's surface, containing dissolved gases and crystals. When magma erupts onto the surface, it is called lava.

The slow circulation of material within Earth's mantle driven by internal heat, which is the primary mechanism driving plate tectonics.

Rock that has been transformed from a pre-existing rock (protolith) by heat, pressure, or chemically active fluids without completely melting.

A naturally occurring, inorganic solid with a characteristic chemical composition and a crystalline atomic structure.

A qualitative scale of mineral hardness ranging from 1 (talc) to 10 (diamond), used in mineral identification based on scratch resistance.

The scientific study of life in the geological past through the examination of fossils, including the organisms' evolution, interactions, and environments.

The branch of geology that studies the origin, composition, distribution, and structure of rocks.

The process by which new oceanic crust is formed at mid-ocean ridges as tectonic plates diverge and magma rises to fill the gap.

Rock formed from the accumulation and lithification of sediment (clastic), precipitation of minerals from solution (chemical), or accumulation of biological material (biochemical).

The branch of geology concerned with the study of rock layers (strata), their formation, composition, distribution, and the information they provide about geological history.

A region where one tectonic plate descends beneath another into the mantle, typically producing deep ocean trenches, volcanic arcs, and intense seismic activity.

Large, rigid segments of Earth's lithosphere that move, interact, and deform at their boundaries, producing seismic and volcanic activity.

A buried erosion surface or gap in the rock record representing a period during which deposition ceased, erosion occurred, or both.

The in-place breakdown and alteration of rocks and minerals at or near Earth's surface by physical, chemical, and biological processes.