Country rock (geology)

In geology, country rock is the rock native to an area, in contrast to any intrusion of viscous geologic material, commonly magma, or perhaps rock salt (in salt domes) or unconsolidated sediments.[1]

A dike (dark) intrudes into the country rock (light), Baranof Island, Alaska, United States
All of "Devonian and younger", "Silurian", and "Ordovician" are country rock. The igneous intrusion leads to a volcanic eruption.

Magma is typically less dense than the rock it intrudes, widening and filling existing cracks, sometimes melting the already-existing country rock.[2]

The term "country rock" is similar to, and in many cases interchangeable with, the terms basement and wall rocks.

Country rock can denote the widespread lithology of a region in relation to the rock which is being discussed or observed.

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