hot knives slicing country rock, Texas
Two out of Three Dike Hill's set of Tertiary intrusions, about 8 miles southeast of Redford, Texas.
The dikes intruded older, layered sedimentary rock. Whatever rock that igneous rock intrusions cut though is called 'country rock'. Somewhere in the vicinity an igneous intrusion found it easier to go sideways in the warm zone of plastic rocks at depth in the Earth's crust instead of upwards.
From a fieldtrip along the Rio Grande a while ago.