The creation of New Mexico's present landscape began some 70 million years ago during the Cenozoic era. About this time the Rocky Mountains were born during the Laramide Revolution, a general uplifing of the earth's crust.
The ancient seas that covered most of New Mexico in earlier times slowly diappeared, and along with them went the dinosaurs and abundant marine life of the Triassic, Jurassic and Cretaceous periods.
Volcanic activity has played an integral role in shaping New Mexico's terrain. Evidence of centuries of volcanism is apparant accross the state.
Valle Grande, located in the center of the Jemez Mountains, is one of the world's largest calderas. The violent eruption that created it released over 75 cubic miles of molten rock, which slowly cooled as it flowed over the land. Today the crater contains 176 square miles of meadow land where wildflwers bloom and cattle graze peacefully. Hotsprings surround this area.
Seismic Activity continues to alter the land. Tension in the earth's crust along a pair of parrallel fault lines running down the center of New Mexico has resulted in the formation of the great Rio Grande Rift Valley. This huge trough, which contains the Rio Grande, is 30 miles across at Albuquerque and widens considerably to the south.
Many of the state's mountains, including the Sandia, Manzano and Sacramento ranges were formed from fault blocks that were tiltied and raised as the earth's crust uplifted.
In New Mexico's arid environment, water is a scarce and precious resource that is, nevertheless, a powerful force in sculpting the geological features
--parts taken from New Mexico Magazine Vacation Guide
Rec. the Environment