Intrusive Rocks In the volcanology branch of geology, intrusive rocks are igneous rocks that form and crystallize under the Earth’s ground surfaces, within other geologic formations. In fact, intrusive rocks form by the process of magma shooting through pre-existing sedimentary, igneous or metamorphic rocks. For instance, a pegmatite dyke or a batholith. On the other…

Zoning Mineralogy Definition Zoning is a variation of crystal composition that is a characteristic of feldspars. To illustrate, the center of a feldspar mineral is formed by a high-temperature phase, whereas the exterior is formed by a low-temperature phase.

Surface-Wave Magnitude “Surface-Wave Magnitude” is the magnitude of an earthquake that scientists estimate using measurements of the amplitude of surface waves.

Runoff (R) The term “Runoff” (R) in hydrogeology and geology refers to the part of rainfall which accumulates on the ground surface and naturally forms into flowing streams.

Anion Anion: In the fields of chemistry and geochemistry, an anion is a negatively charged ion. The oppositely charged ion is a cation.