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Colorado Plateau
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Colorado Plateau

The Colorado Plateau, also called the Colorado Plateaus Province, is a physiographic province of the Intermontane Plateaus of North America that is roughly centered on the Four Corners region of the southwestern United States and is composed of fault-bounded plateaus. The province is bounded by the Basin and Range Province (the Great Basin is rough geographic equivalent) to the west, south, and southeast and by the southern and central Rocky Mountains to the east and north. The rock units that make up these plateaus are mostly flat-lying sedimentary rock that are between 5000 feet (1500 m) to 11,000 feet (3350 m) above sea level and the province covers an area of 130,000 square miles covering parts of Colorado, Utah, and Arizona. The crust of the region is 35 to 50 kilometers (22 to 30 miles) thick while the crust of the Basin and Range is 20 to 30 kilometers (12 to 19 miles) thick. A supersequence of these rocks are exposed in the various cliffs and canyons (including the Grand Canyon) that make up the Grand Staircase.

Table of contents
1 Geology
2 Protected lands
3 References

Geology

The Precambrian history of the Colorado Plateaus is only known at its southern end where the Grand Canyon has exposed the 2000 million year old Vishnu Schist to the 600 million year old Kaibab Limestone. Most of the formations were deposited in warm shallow seas and near-shore environments (such as beaches and swamps) as the seashore repeatedly advanced and retreated over the edge of a proto-North America (for detail see geology of the Grand Canyon area). The province was probably on a continental margin throughout the late Precambrian and most of the Paleozoic era.

In late Paleozoic and much of the Mesozoic era the region was affected by a series of orogenies (mountain-building events) that deformed western North America and caused a great deal of uplift. Now above land, streams, ponds and lakes created formations such as the Chinle, Moenave, and Kayenta. Later a vast desert formed the Navajo and Temple Cap formations and dry near-shore environment formed the Carmel (see geology of the Zion Canyon area for details).

The area was again covered by a warm shallow sea when the Cretaceous Seaway opened in late Mesozoic time. The Dakota Sandstone and the Tropic Shale were deposited in the warm shallow waters of this advancing and retreating seaway. Several other formations were also created but were mostly eroded following two major periods of uplift.

The Laramide orogeny created uplift that closed the seaway and uplifted a large belt of crust from Montana to Mexico with the Colorado Plateau region being the largest block. Thrust faults in Colorado are thought to have formed from a slight clockwise movement of the region, which acted as a rigid crustal block. Minor uplift events continued through the start of the Cenozoic era and was accompanied by some basaltic lava eruptions and mild deformation. The colorful Claron Formation that forms the delicate hoodooss the Bryce Canyon is famous for was then laid down as sediments in cool streams and lakes (see geology of the Bryce Canyon area for details).

Tectonic activity resumed in Mid Cenozoic time and started to unevenly uplift and slightly tilt the Colorado Plateaus region starting 20 million years ago. Streams had their gradient increased and they responded by downcutting faster. Headward erosion and mass wasting helped to erode cliffs back into their fault-bounded plateaus, widening the basins in-between. Some plateaus have been so severely reduced in size this way that they become mesas or even buttes. Monoclines form as a result of uplift bending the rock units. Eroded monoclines leave steeply tilted resistant rock called a hogback and the less steep version is a cuesta.

In the west, crustal extension created the Basin and Range Province along with major faults, such as the Hurricane Fault, that separate the two regions. The dry climate was in large part a rainshadow effect resulting from the rise of the Sierra Nevada further west.

The Pleistocene epoch brought periodic ice ages and a cooler, wetter climate. This increased erosion at higher elevations with the introduction of alpine glaciers while mid-elevations were attacked by frost wedging and lower areas by more vigorous stream scouring. Pluvial lakes also formed during this time.

Glaciers and pluvial lakes disappeared and the climate warmed and became drier with the start of Holocene epoch.

Protected lands

Covering a large part of the Colorado River catchment, this relatively high semi-arid province produces many distinctive erosional features such as arches, arroyos, canyons, cliffs, fins, natural bridges, pinnacles, hoodooss, and monoliths that, in various places and extents, have been protected. There are eight national parkss, more than a dozen national monuments and dozens of wilderness areas in the province along with millions of acres in national forests and other protected lands.

;National parks (from south to north clockwise):

;National Monuments:

;National Forests:

;Wilderness areas:
  • Kachina Peaks Wilderness
  • Strawberry Crater Wilderness
  • Kendrick Mountain Wilderness
  • Beaver Dam Mountains Wilderness
  • Pauite Wilderness
  • Grand Wash Cliffs Wilderness
  • Mount Logan Wilderness
  • Mount Trumbull Wilderness
  • Kanab Creek Wilderness
  • Cottonwood Point Wilderness
  • Paria Canyon-Vermilion Cliffs Wilderness
  • Saddle Mountain Wilderness
  • Mount Baldy Wilderness
  • Escudilla Wilderness
  • Black Ridge Canyons Wilderness
  • Flat Tops Wilderness
  • Uncompahgre Wilderness
  • Mount Sneffels Wilderness
  • Lizard Head Wilderness
  • Weminuche Wilderness
  • South San Juan Wilderness
  • Cebolla Wilderness
  • West Malpais Wilderness
  • Bisti-De-Na-Zin Wilderness
  • Pine Valley Mountain Wilderness
  • Ashdown Gorge Wilderness
  • Box Death Hollow Wilderness
  • Dark Canyon Wilderness
  • High Uintas Wilderness

Other notable protected areas include: Glen Canyon National Recreation Area, Dead Horse Point State Park, Kodachrome State Park, Goblin Valley State Park and Barringer Crater (meteor crater).

References