Since then, erosion has lowered the surface hundreds of meters, exposing the deeper levels of these extinct volcanoes. Shiprock, shown above, is a classic example of a volcanic neck or plug. This is the feeding conduits of the volcano that has been filled with magma or volcanic breccia. All photos by Steve Mattox. The volcanic plugs or necks of the Navajo volcanic field form crudely cylindrical masses.
Dikes radiate from the neck.
This is the remains of the shallow interior of the volcano. Photo along one of the radial dikes at Shiprock. Cross-section of Agathla volcanic neck. The main body of tuff breccia is cut by dikes of minette. At the original surface, the conduit probably terminated at a maar .