Black Canyon of the Gunnison - Pt. 3

Weathering and Hydrology of the Canyon

The Black Canyon was formed relatively quickly over the last 2 million years by down-cutting very resistant Precambrian bedrock. Because the water had no choice, it was forced to cut through the canyon and the canyon floor continues to erode at a rate of 1 foot per thousand years.

(photo at left from http://wwa.colorado.edu/western_water_law/)

Because the metamorphosed granite is so resistant, the sides of the canyon weather and erode very slowly. However, some weathering does occur such as the freeze-thaw cycles that create frost action weathering that contributes to mass wasting of the canyon walls. In the steep areas of the canyon, large columns of rocks break away and form areas of talus in parts of the canyon

(the photo at right shows a dark, snowy area of talus).

The Gunnison River get its water from the snowmelt and limited rainfall of the Western slopes of the Continental Divide as it races through the Black Canyon to join the Colorado River. The Blue Mesa Dam creates a reservoir (see reservoir in photo below) that decreases the river’s erosion power but provides water for irrigation and public use on the western slope, as well as a place for recreation. The water from this river is a partially-renewable ground water resource that is a critical source for domestic water in the area.

Other sources:

http://www.ux1.eiu.edu/~cfrbj/parks/blca/blca2.htm

Some info on water rights in the area: http://www.waterinfo.org/gunnison-river

The Essential Guide to Black Canyon of the Gunnison National Park

By John Jenkins (p. 45) retrieved from http://books.google.com/books?id=W31yWpLZMxUC&pg=PA45&lpg=PA45&dq=black+canyon+weathering&source=bl&ots=xCohv3pL9l&sig=vnlwJmiCsSvg5FuxurEug43mdjU&hl=en&ei=qFabTavrDZTAsAPJubGIBA&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCcQ6AEwAg#v=onepage&q=black%20canyon%20weathering&f=false

Black Canyon of the Gunnison - Pt. 2

The Black Canyon of the Gunnison: Evidence of the creation of Colorado

Located on the North American Plate, the basement rock of the canyon provides evidence that Colorado has oceanic crust; ~1.7 Ga, plate tectonics brought an oceanic volcanic arc to collide with the continental shores of Wyoming.

The heat- and pressured-tempered offspring of that union are metamorphic Gneiss and Schist interlaced with pinkish igneous pegmatite dikes of muscovite, potassium feldspar and quartz minerals (see photo- Painted Wall, Black Cayon of the Gunnison, Colorado -right).

Between the Entrada Sandstone and Precambrian rocks exists a Great Unconformity where millions of years of geologic history have vanished.

How the Black Canyon came to be:

The Gunnison basin was uplifted (72 Ma) and later covered with ~4,000 feet of debris from explosive, basaltic volcanism from ranges in the area; cinder and ash fall along with ash and mud flow built up the West Elks and forced the stream between the two uplifted areas. The rushing water of the Gunnison river had no choice but to cut over the hard-to-erode Precambrian basement.

A combination of a steep river gradient, glacial melt and debris, river erosion, mass wasting, impressive seasonal flooding, and no other choice led to the glorious steep Black Canyon of the Gunnison.

References:

To find a 1976 map of known faults in Colorado visit: http://ngmdb.usgs.gov/Prodesc/proddesc_15251.htm

Other:

http://www.cliffshade.com/colorado/black_canyon/

http://www.cliffshade.com/colorado/tectonics.htm

http://www.nature.nps.gov/geology/parks/blca/index.cfm

Black Canyon of the Gunnison National Park - Pt. 1

Welcome to Colorado! The first adventure we
recommend is the stunning, and slightly scary, Black Canyon of the Gunnison National Park!

Located in Montrose, Colorado 81401, the park is on the Western slope of Colorado near the town of Gunnison, and the Gunnison River flows right through the deepest canyon in mountainous Colorado.

Lat: -107.72506713867188
Long: 38.586820096127674
Click here to see a small-scale map of the surrounding area! (right click and choose "open in a new tab")

Time zone: MST, MDT
Click here to see what time it is at the Black Canyon right now! (right click and choose "open in a new tab")

Famous for its steep cliffs, the Black Canyon is named because some parts of the canyon remain untouched by sun throughout the year. Some of the oldest rocks on the planet can be seen exposed in the depths of the canyon - Precambrian rock that is over 2 BILLION years old!

There are several routes throughout the national park on which visitors can drive or hike to see the glorious interaction of geographic systems.

Click here to see a park map! (right click and choose "open in a new tab")

Humans are encouraged to check out the visitor's center at the rim of the canyon and discuss the amazing features of the park with a knowledgeable Park Ranger or walk out to the overlook and view the dizzying depths for themselves!

Click here to see a topographic map of the park (from PICKATRAIL.com)! (right click and choose "open in a new tab")

Park map and area map provided by Black Canyon of the Gunnison National Park information page at NPS.com. Click here to go directly to that site! (right click and choose "open in a new tab")