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Students take Southwestern "sedimental journey"

MIT students taking an IAP environmental geology field course had the unusual experience of seeing a very wet desert as they worked their way around Nevada and Southern California for 11 days in mid-January.

"There is no substitute for hands-on study," said Sam Bowring, associate professor of geology and lead instructor on the trip. "Observation of geologic processes-including human influences-is a critical part of understanding earth history. It gives students a new respect for the power of these processes, the immensity of geologic time and the fragility of our environment."

Throughout the course, the 16 students, led by Professors Bowring, Timothy Grove and teaching assistant Dave Hawkins, could see and discuss a variety of topics concerning natural and human-induced effects on the environment. These included massive volcanic eruptions, earthquake hazards, landslides, air and water pollution, water shortage issues and the proposed nuclear waste site at Yucca Mountain.

The high rainfall and resulting erosion was an unanticipated bonus for this year's trip. While jokes about the "Mojave Mud Bowl" proliferated, the students had the opportunity to see dry stream beds flow with water and braided streams carry their high sediment loads downstream.

The areas in which the group traveled also clearly showed effects of seismic and tectonic activity. Deeply cut, or dissected, alluvial fans-aprons of eroded sediment that surround the mountains-provide evidence of uplift of the earth's crust. Several volcanic cinder cones and faults were also on the itinerary.

"In Nevada and California we have the opportunity to observe a much more techtonically active earth than in our relatively quiet New England, " Professor Bowring said. "Deformation of rocks at rates of 0.5 cm/year results in spectacular folding of the rocks, uplift of mountains and erosion, when integrated over one or two million years-an instant to most geologists."

By traveling to the Southwest, the students were able study geological processes more easily than in New England because of sparse vegetation. In the Valley of Fire in eastern Nevada, for example, students could easily see dramatic rock formations and study the curving layers of sand particles in the rock formed by sand movement on advancing and shifting sand dunes.

At another site, the group studied the Blackhawk Landslide. Here it is theorized that the rock sheared off the side of a mountain, became fluidized on a cushion of air, and in 80 seconds covered an area one to two miles wide and five miles long with a blanket of rock 50 to 100 feet thick.

The field course included lectures and demonstrations packed into a full schedule. The group would often be up before sunrise, pack up camp, have breakfast and be on the road by 7:30am. After a full day of driving and hiking the vans would pull into a campsite and once again camp would be set up and dinner cooked.

At the Coso geothermal plant on the grounds of the China Lake Naval Air Weapons Station, the students observed an alternate method of energy production. Amid a number of fumeroles, where hot gases from the earth escape into the atmosphere in clouds of steam, workers drill wells up to 11,800 feet deep to bring heated water and gas to the surface, generating 250 megawatts of power. The plant was developed by special arrangement between the Navy and a private energy company both to reduce the Navy's energy bill and to use alternate energy sources. The plant provides all of the power requirements of the military base, and the additional energy generated is sold to Southern California Edison.

Water shortage and management issues were also discussed on the trip. It seemed appropriate that the vans from MIT, whose mascot is a beaver, head to the Hoover Dam, constructed in the 1930s for flood control, water distribution and power generation. There at Lake Mead the group could see the clear white ring of salts that remained-meters high on the walls of the reservoir-after evaporation because of high desert temperatures and the fluctuation of the water table.

The movement of water westward to supply California's more populated coastal areas was evident in Owens Valley. where the group saw that even in a desert climate, water is often transported in open canals. Starting in 1913, water was diverted from the Owens River to irrigate the San Fernando Valley. By 1926, Owens Lake was dry. The empty lake bed now resembles a toxic waste dump, its white crust caused by salt deposits left behind by the evaporated and drained lake. The salts, though not considered toxic waste, are agents of rapid decay. Fallen logs in the area have lost all but their cellulose and break apart like fiberglass insulation.

The Ubehebe Crater whose walls drop at an angle of nearly 30 degrees in Death Valley provided hiking variety and challenge. The group had great fun walking, or rather bouncing, down the loose gravely slope like skiers in the depths of moguls. Coming back up was another story-one step up and a half step back. The 500-foot climb caused even those in top condition to take a break to enjoy the view.

(The author took an EAPS field course this year following a fall Environmental Earth Science course.)

A version of this article appeared in MIT Tech Talk on March 1, 1995.

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