Hi All. Just thought a little geological history of the Raton-Clayton volcanic field, which is related to the Rio Grande rift would be nice to know.

First we must start with the Rio Grande rift, which is the cause of Raton-Clayton volcanic field. The Rio Grande rift first developed as a chain of closed basins or half grabens (trench-like features formed by down-dropped blocks of crustal rocks), which gradually filled with lava, ash flows, and sediments that washed in from nearby mountain ranges.

The Rio Grande rift is geologically young and resulted from a process of regional extension and mantle upwelling in Neogene times. The Rio Grande rift continues to widen today, and ongoing geologic activity is evident through high heat flow, hot springs, continued seismicity, geodetic observations, and some of North America's most recent lava flows.

The Rio Grande rift got its start 29 million years ago in the Leadville, Colorado area. Two major episodes of extension have formed the Rio Grande rift. The fist occurred in late Oligocene to early Miocene time beginning 29 million years ago and lasting 10 to 12 million years. Strain rates were less during this early phase of rifting, except where volcanism and high heat flow caused local concentration of extensional strain.

Rifting began to separate the Colorado Plateau from the Great Plains. West of the rift the crust of the Colorado Plateau is approximately 45 kilometers thick; east of the rift the crust beneath the Great Plains is 50 kilometers thick; beneath the rift zone the crust is only 35 kilometers thick (Chapin and Cather, 1994).

There is much more to this rift then what I have just shown. Go take a look see. Take Care…Don in creepy town

• Rio Grande Rift