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Archive for June, 2011

Walden students in Moab

Walden students at the Arches National Park visitor center

Between third and fourth terms, Walden School holds a two-week Intersession that includes high interest classes (such as the CSI class I reported on last post) and often also includes a field trip. This year we traveled to Moab, Utah which is the gateway for some of the most incredible scenery, geology, and adventure activities you can find anywhere. The town is situated in a valley between two national parks (Arches and Canyonlands), a mountain range (the La Sals), and next to the Colorado River.

Moab is the last place on the river that is easily accessible for putting boats in and out until you get all the way down to Lake Powell and Bullfrog Marina. If you want boating, kayaking, bicycling, hiking, slick rock four-wheeling, camping, or just photo opps, this is the place. It’s also an interesting place for unearthing the elements.

Charlie Steen

Charlie Steen in 1961

Moab was a sleepy town in the early 1950s when an unlikely discovery changed everything. Charlie Steen was a geologist and prospector who had heard that uranium was a byproduct of the vanadium mines scattered around the American southwest. The Atomic Energy Commission needed domestic sources of uranium and set an artificially high price for it as an incentive for prospectors and miners to discovery new sources, and Steen headed to Utah to seek his fortune.

Steen had a theory that uranium might accumulate in an anticlinal structure just as oil does, and the area around Moab consists of underground salt domes deposited about 350 million years ago when a mountain range known as the Uncompaghre Uplift covered what is now the border between Utah and Colorado. A large syncline called the Paradox Basin formed just west of this mountain range, and during the Pennsylvanian and Permian periods it was filled with a shallow ocean. This sea frequently dried up, leaving huge layers of salt, which were eventually covered with sand dunes (now the Navajo and Entrada sandstones) and the Mancos shale layer during the Mesozoic Era. The weight of these overlying layers caused the salt layers to shift and bulge in places and form depressions in others. The Moab Valley is one of these depressions, and Arches National Park is one of the domed up areas. As the salt bulged up, it cracked the sandstone layers into a series of parallel cracks. Water got into the cracks and created fins, or thin ridges which eventually eroded further into the arches that the area is famous for. But underneath it all lies the salt. Steen felt that any uranium that eroded off of the ancient Uncompaghre Mountains would accumulate in the Paradox Basin and be deposited in the sandstone found there, now pushed up into an anticline.

Rock fins

Eroded remnants of rock fins in Entrada Sandstone at Arches National Park

Everyone else thought this theory was ridiculous. Uranium in sandstone? Impossible! Steen spent two years prospecting through the area living in a tarpaper shack, feeding his family on poached venison. He didn’t even have enough money to buy a Geiger counter to check samples for radioactivity. Then, in 1952, he struck a deposit of high-grade pitchblende ore in the Lisbon Valley southeast of Moab and named it the Mi Vida (“My Life”) mine. Suddenly rich, he invested in various other mines and uranium mills, built a large house on the edge of the cliff overlooking Moab, and made sizable donations to build the local hospital and to improve the airport, and even flew in a private plane to Salt Lake City once a week for dance lessons.

Mining Districts of Utah

Mining Districts of Utah. Uranium/Vanadium deposits are shown in green.

Steen’s success started a uranium boom in southeast Utah, and other deposits were soon discovered. They were mostly located in three major areas (as shown by this map of Utah’s mining districts – the green areas are uranium/vanadium mines). The first area centered around Moab and the Paradox Basin. A second major area was around the edges of the San Rafael Swell. The third was along White Wash, a remote area east of present-day Lake Powell. Uranium processing mills were built at Moab and Monticello, and the area prospered as money and jobs poured in.

By the mid-1960s the U. S. Government decided it had enough uranium stockpiled and stopped purchasing it. The price fell, and the boom days were over. Unfortunately, radiation from the tailings piles at the mills had so contaminated the two towns that the incidence of cancer is greatly increased compared to similar populations elsewhere. Both tailings piles are being removed and reprocessed to make them safe.

Double Arch

Double Arch at the Windows Section, Arches National Park

For our trip to Moab, we stayed in small cabins at an RV park at the north end of town. The weather, being March, was windy with a storm front moving in slowly from the northwest as we left Provo, but traveling east we got ahead of the storm and found the weather nice when we arrived around noon on Wednesday. The group split into two parties, one going to the Fiery Furnace in Arches NP and the rest going to the Windows Section (my favorite area). I took some photos and video of Double Arch, Balanced Rock, the La Sal Mountains, and other areas between the Park entrance and Windows Section.

The La Sal Mountains

The La Sal Mountains and Windows Section, Arches National Park

On Thursday, most of the group hiked in to Delicate Arch. The weather had turned colder and more threatening as the front slowly approached, but it was a nice hike to the arch (about 1.5 miles). Along the way, at the backside of the first hill, is an unusual rock formation of purplish chert. It was formed from the same red sandstone all around us, but here there was a fault line caused by the buckling of the underlying salt domes. As the two sides of the fault moved against each other,  contact metamorphism converted the sandstone to chert, the red iron oxide turning purplish as it often does when metamorphosed.

Delicate Arch

Delicate Arch in Arches National Park, Utah

Chert boulder on trail to Delicate Arch

Chert boulder on the trail to Delicate Arch

After Delicate Arch we hiking into Landscape Arch, then returned to camp as the day turned colder. We ate dinner in Moab as a faculty at a decent pizza place as it finally started to rain, and enjoyed the hot tub that evening. On Friday we packed up and headed back to Provo.  I was able to get some great photos of the geologic features of Arches National Park.

Landscape Arch

Landscape Arch in Arches National Park

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