The Colorado Plateau of Arizona, Colorado, New Mexico, and Utah is made of mostly flat-lying layers of sedimentary rock that record paleoclimate extremes ranging from oceans to widespread deserts over the last 1.8 billion years. Navajo Mountain in southeastern Utah is a dome-shaped chunk of igneous rock that intruded into the sedimentary layers and lifted up the overlying layer. Navajo Mountain is one of several of these rock formations, called laccolith by geologists, in southeastern Utah’s portion of the Plateau. This oblique (from-the-side) astronaut photograph highlights Navajo Mountain in the center of the image, surrounded by light red-brown Navajo Sandstone (also visible in the canyon at bottom of the image). The igneous rock at the core of the mountain is wrapped in sedimentary layers. The peak of Navajo Mountain, at approximately 3,148 meters (10,388 feet) elevation, is comprised of uplifted Dakota Sandstone deposited during the Cretaceous Period (approximately 66-138 million years ago).
Published Oct 31, 2005
In the northwest corner of Colorado, the west-flowing Yampa River meets the south-flowing Green River, which runs into Utah. Stretches of both river canyons upstream and downstream from the junction make up Dinosaur National Monument. The monument takes its name, of course, from the abundant fossils found in exposed valleys and low ridges of the Morrison Formation, a series of rock layers that were formed late in the Jurassic Period, roughly 145 million years ago.
Published Oct 1, 2007
