Magma bodies in the Rio Grande rift in central New Mexico
— Allan R. Sanford

Magmatism is considered an important component in the develop-ment of many continental rifts, yet the small number of active volcanoes along continental rifts (MacDonald, 1972) suggests that movement of detectable amounts of magma from the upper mantle into the crust may be a relatively rare geologic occurrence. Geologic studies in the Rio Grande rift indicate that large-scale volcanic activity has indeed taken place at widely separated locations at widely spaced times (Lipman and Mehnert, 1979; Luedke and Smith, 1978). Hence, there are geologic reasons for believing that magma bodies will not be found along the entire length of the Rio Grande rift, and geophysical studies to date appear to bear this out.

The Socorro area is the one region of the Rio Grande rift where a suite of geophysical observations indicates the existence of magma in the crust. Particularly well established is the depth and extent of a sill- shaped magma body at mid-crustal levels.