Country rock (geology) in geology when the term "country rock" is used include: When describing a pluton or dike, the igneous rock can be described as intruding the surrounding "country rock", the rock into which the pluton has intruded. When country rock is intruded by dyke, it is called "discordant intrusion," while intrusion by a sill indicates a "sub-parallel" or "concordant intrusion". Most intrusions into country rock are via magma. Usually, country rock is intruded by an igneous body of rock which formed when magma forced upward through fractures, or melted through overlying rock. Magma then cooled into solid rock, different from the
Fort Rock for lost cattle. Fort Rock was created when basalt magma rose to the surface and encountered the wet muds of a lake bottom. Powered by a jet of steam, molten basalt was blown into the air, creating a fountain of hot lava particles and frothy ash. The pieces and blobs of hot lava and ash rained down around the vent and formed a saucer-shaped ring of lapilli tuff and volcanic ash sitting like an island in the lake waters. Steam explosions also loosened angular chunks of black and red lava rock comprising the valley floor. These blocky inclusions are incorporated