A subcircular to circular dike with steep dip. Ring dikes may be many kilometers long, and hundreds or thousands of meters thick. Their radius is generally from 1 to 20 km. Although some ring dikes may form a nearly complete circle, more commonly they encompass 1/4 to 3/4 of a circle or ellipse. They are commonly associated with alkalic igneous complexes and carbonatites, so are probably related to deep shock effects or to cauldron subsidence. Ring dikes are commonly associated with cone sheets to form a ring complex.