Rock (geology)

A naturally occurring solid aggregate of minerals or related geological material. Its composition, porosity, cracks and fluid content affect seismic wave speeds and magnetic susceptibility.

Relatively consolidated rock beneath loose cover. A geophysically defined bedrock interface can be an operational seismic velocity or stiffness boundary and need not coincide with crystalline basement.

A rock dominated by magnesium- and iron-rich minerals, with lower silica content than typical mafic rocks. Alteration can strongly change its magnetic properties.

A rock relatively rich in magnesium- and iron-bearing silicate minerals. Basalt and gabbro are common examples; their magnetic susceptibility depends particularly on magnetic-mineral abundance.