After about 500 km (311 mi) travel westward, our trip swings to the southwest as it moves over the Colorado Plateau. The Plateau includes a small part of western Colorado and northwestern New Mexico, much of northern Arizona and a substantial part of Utah. The scene shown here includes the meeting of these states at

the Four Corners - the only place in the U.S., in which that many states touch each other at one point. Unfortunately, we can’t discretely identify the point, but it lies about 30% up and 15% in from the lower right corner of the image).

Many people consider this the most scenic of all provinces in the U.S. because of its marvelous landforms and its colorful rocks. Many of its mainly Upper Paleozoic and Mesozoic rock units are bright reds, oranges, and yellows, whereas others are light to dark gray to brown. To the southwest of this scene, the Grand Canyon¾ the most famous feature in the Plateau¾ exposes typical, multi-colored units. Bryce, Zion, and Canyonlands National Parks also display spectacular colored rocks. This false color image, taken in January, approximates some of these colors. At this time of year the sparse vegetative cover of sage, mesquite, and grasses does not produce a typical red signature, so that the surface tones are entirely those of rock and soil.

The rocks are almost everywhere still in the subhorizontal positions, in which they were deposited as sediments. Because they erode along steep faces or scarps, where cap rock is hard, the layers stack like steps to form plateaus, mesas, and buttes. The Gothic Mesas, just to the right of image center, are typical. Monument Valley, a classic cluster of mesas that are often seen in movie Westerns, begins near the lower left corner. The Plateau has participated in the general deformation of the West chiefly by uplifting without folding. However, Combs Ridge, a prominent monocline (like the Waterpocket Fold) is evident about 15-20% in from the left edge of the image. Near the bottom right corner are the snow-capped Carrizo Mountains, partially volcanic in origin, which rises at Pastora Peak to 2,870 meters (9,414 ft). These highlands blend into the Chuska Mountains to the south, just out of view..

This barren region has a very low population. Part of the scene includes the Navajo Indian Reservation. The small towns of Mexican Hat and Bluff in Utah lie along the San Juan River. At center left, this river has entrenched (deeply downcut) its meanders to produce steep canyon walls that make up the picturesque Goosenecks. Just to the west of the image, the San Juan River joins the Colorado River, upstream from the artificial Lake Powell, formed by the Glen Canyon Dam. Finally, there is a "streakiness" in much of the lower part of the image. Prevailing winds, re-enforced by joint (fractures) control of landscape erosion, cause this effect.

6-10: What causes "goosenecks"? ANSWER

Collaborators: Code 935 NASA GSFC, GST, USAF Academy
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