Utah’s Glacial History

Moraine with erratics, Photo Courtesy and Copyright Mark Larese-Casanova, Photographer
Moraine with erratics
Photo Courtesy & Copyright
Mark Larese-Casanova, Photographer

Little Cottonwood Canyon, Photo Courtesy and Copyright Mark Larese-Casanova, PhotographerLittle Cottonwood Canyon
Photo Courtesy & Copyright
Mark Larese-Casanova, Photographer

Hi, this is Mark Larese-Casanova from the Utah Master Naturalist Program at Utah State University Extension.

It is amazing to see just how much of an impact the large amount of snowfall from last winter still has on the annual cycle of nature. Of recent note, wildflower blooms in the mountains seem to be at least 2-3 weeks behind normal schedule. Hiking through snow in late July had me thinking about colder times when Utah’s mountains were covered with ice that flowed as glaciers.

The most recent period of glaciation in Utah occurred between 30,000 and 15,000 years ago when Utah’s climate was, on average, up to 30?F cooler. At times during this period, much of the western half of Utah was covered by Lake Bonneville, which contributed tremendous amounts of moisture as snow throughout Utah’s mountain ranges. As the snow accumulated at high elevations, its sheer weight caused it to recrystallize into ice. Once the masses of ice became heavy enough, gravity pulled them down slope, carving out characteristic U-shaped valleys.

At the top of the valleys, where the glaciers formed, we can often find large, bowl-shaped cirques. In the Wasatch Range, the Little Cottonwood Canyon glacier formed at the top, creating Albion Basin, and reached the mouth of the canyon where calved icebergs into Lake Bonneville. The Uinta Mountains contained such large glaciers that even many of the mountain peaks are rounded.

As temperatures warmed during the end of the last ice age, glaciers receded and left behind large piles of soil and rocks, known as moraines. Terminal moraines at the end of a glacier’s path, can act as natural dams to create lakes. Enormous boulders, known as glacial erratics, can often be found discarded along canyons.

While glaciers don’t currently exist in Utah, there are several permanent snowfields in shaded high mountain areas. So, if you’re feeling a little nostalgic and missing that extra long winter we had this year, you still a chance to hike up above 9,000 feet and cool your toes in the snow.

For Wild About Utah, I’m Mark Larese-Casanova.

Credits:

Images: Courtesy & Copyright Mark Larese-Casanova
Text:     Mark Larese-Casanova, Utah Master Naturalist Program at Utah State University Extension.

Additional Reading:

Utah Geological Survey http://geology.utah.gov/surveynotes/gladasked/gladglaciers.htm

Parry, William T. 2005. A Hiking Guide to the Geology of the Wasatch and Uinta Mountains. University of Utah Press.

Stokes, William Lee. 1986. Geology of Utah. Utah Museum of Natural History.

Red Rock Country

Chinese Wall at Bryce Canyon National Park
Courtesy NPS.gov
http://www.nps.gov/brca/

Straddling the 4 corners region is a massive geologic province known as the Colorado Plateau. Varying from 5 to 10,000 feet in elevation the region covers an area larger than the state of New Mexico, and is composed of thick horizontal layers of sedimentary rock . Terrain here is flat compared with Basin and Range country to the west and the Rocky Mountains to the east. Yet wind and water have whittled Plateau rock into dramatic cliffs and steps as well as fanciful domes, towers, turrets, and arches. The Plateau is dissected by the Colorado River and its tributaries exposing a deep and colorful geologic history. A predominance of red bed deposits in the central area of the Plateau has prompted the nickname “red rock country.”

So what’s behind the spectacular hues for which Utah is so famous? The color of rock is primarily influenced by trace minerals. The red, brown, and yellow colors so prevalent in southern UT result from the presence of oxidized iron–that is iron that has undergone a chemical reaction upon exposure to air or oxygenated water. The iron oxides released from this process form a coating on the surface of the rock or rock grains containing the iron.

Just think of what happens to a nail when you leave it outside. Upon prolonged exposure, the iron in the nail oxidizes and rust is formed as a coating on the surface of the nail. So basically what we have in red rock country is a lot of rusting sandstones and shales. Hematite is an especially common mineral form of iron oxide in Utah, the name coming from the Greek word “heama” or red blood. It only takes a tiny bit of hematite make a lot of red rock.

Geologists refer to rock layers of similar composition and origin within a given geographic area as “formations.” Certain formations in Utah are especially known for their beautiful reds or pinks. The Permian Period gave us Organ Rock shale which caps the buttes and pinnacles of Monument Valley. The deep ruddy browns of the Moenkopi formation were formed in the Triassic. In the early Jurassic, eastern Utah was a vast sea of sand with wind-blown dunes. These dunes became the red bed deposits of the Wingate Formation which today forms massive vertical cliffs. Entrada sandstone, from the late Jurassic, forms the spectacular red, slickrock around Moab.

Well anyway, now you know what I’m thinking of when I hear Utah referred to as a Red State. I’m picturing the extraordinary beauty of the red, salmon and rust- brown rocks that help to form the massive geologic layer cake in the south and east of our state.

For Wild About Utah and Stokes Nature Center, I’m Holly Strand.

Credits:
Photo: Courtesy NPS.gov: http://www.nps.gov/brca/
Text: Stokes Nature Center: Annalisa Paul

Sources & Additional Reading

Chan,Marjorie A. and William T. Parry Rainbow of Rocks . Public Information Series 77. Utah Geological Survey. http://geology.utah.gov/online/pdf/pi-77.pdf (Accessed July 2008)

Geology Underfoot in Southern Utah by Richard L. Orndorff, Robert W. Wieder, and David G. Futey, Missoula, MT Mountain Press Publishing Company, 2006, http://mountain-press.com/item_detail.php?item_key=366

Chronic, Halka. Roadside Geology of Utah. Missoula, MT Mountain Press Publishing Company, 1990 http://mountain-press.com/item_detail.php?item_key=48

Fillmore, Robert, The Geology of the Parks, Monuments and Wildlands of Southern Utah, University of Utah Press, 2000, http://content.lib.utah.edu/cdm4/item_viewer.php?CISOROOT=/upcat&CISOPTR=1328