Geologists and geographers have divided the United States into many
provinces, each of which has distinctive geologic and topographic
characteristics that set it apart from the others. Colorado National
Monument is in the northeastern part of the Canyon Lands section of the
Colorado Plateau Province—a province that contains 15 national parks and
monuments, about 3 times as many as any other province. This province,
hereinafter referred to simply as the Colorado Plateau, or the Plateau,
covers some 150,000 square miles and extends from Rifle, Colo., at the
northeast to a little beyond Flagstaff, Ariz., at the southwest, and
from Cedar City, Utah, at the west nearly to Albuquerque, N. Mex., at
the southeast. This scenic province consists of high plateaus generally
ranging in altitude from 4,500 feet to more than 7,000 feet, which are
deeply and intricately dissected by literally thousands of canyons.
Colorado National Monument is drained entirely by the Colorado River,
which flows to the northwest in the wide Grand Valley just a few miles
from the northeastern border (fig. 3). The small streams that drain the
Monument contain water only after summer thundershowers or after rapid
snowmelt.
Why is the large valley of the Colorado River called the Grand Valley?
The Colorado River northeast from its confluence with the Green River in
the middle of Canyonlands National Park[17] formerly was called the
Grand River, and the Green and Grand joined at the confluence to form
the Colorado River. The Grand River was renamed Colorado River by act of
the Colorado State Legislature approved March 24, 1921, and approved by
act of Congress July 25, 1921. But the old term still remains in names
such as Grand County, Colo., the headwaters region; Grand Valley, a town
16 miles west of Rifle, Colo.; Grand Valley between Palisade and Mack,
Colo.; Grand Mesa, an extensive plateau which towers more than a mile
above the Grand and Gunnison River Valleys; Grand Junction, Colo., a
city appropriately situated at the confluence of the Grand and Gunnison
Rivers; and Grand County, Utah, which the river traverses after entering
Utah.