A dike is a formation of igneous rock that can form exposed vertical or linear ridges. Dikes are formed underground and are an intrusive plutonic rock formation. Intrusive formations form when upwelling magma cools and solidifies beneath the surface. As the magma rises it intrudes into the overlying country rock (older rock that is also termed "host" rock).

Dikes are vertical formations and thus form at a steep or often near right angle to the surface. Dikes are planar intrusions that, in contrast to horizontal sills, have a discordant form of contact with the host rock into which they intrude. A discordant contact is one that transverses or cuts across the established bedding planes of the country or host rock (e.g., at right angles to surrounding sedimentary bedding planes).

Dike texture varies from aphanitic (no visible mineral crystals) to phaneritic (visible mineral crystals). The texture is determined...