From Vegas to the Valleys
|Location||Southwestern United States|
When someone speaks of incredible scenery and some of the best geological locations in the United States, visions of the American West come to mind. The Denison geology majors were able to experience this firsthand on the 2000 Spring Break field trip. Covering a total of over 1500 miles in California and Nevada, this journey exposed students to some of the best geology in the U.S.
The trip began with a flight from Columbus to Las Vegas, where the group of 15 people rented two large vans and set out for the Mojave Desert. The trip was planned and organized by Dr. David Hawkins, who ran four similar trips over the past 7 years. He and Dr. David Greene led the trip, which began with stops at the Cima volcanic field and Amboy Crater. At The Cima volcanic field, the students walked on a 10,000 year old basaltic lava flow and observed many features that indicated the flow was of the aa variety. Several students discovered a ballistic bread-crust bomb on the surface of the flow more than one mile from the vent. Dr. Hawkins led the students through a brain-storming session in an attempt to understand how the bomb ended up so far from the vent. At Amboy Crater the students climbed into a cinder cone and worked out the eruptive history preserved by the various cinder and spatter ramparts within the main cone. Dr. Hawkins pointed out that the volcano sits within a depression which gives the impression that lava had flowed uphill. Again, the group considered how and, most importantly, when the depression formed. The discussion produced a variety of hypothetical mechanisms based on common sense and some simple geological knowledge. This sense of discovery on the outcrop continued throughout the trip.
From the volcanoes of the Mojave Desert the group traveled northwest to Rainbow Basin and Owl Creek Canyon. At these locations they observed Tertiary lake bed deposits and volcanic ash layers that have been folded and faulted by stresses created by a bend in a strike-slip fault system related to the San Andreas. Dr. Greene used the excellent exposures to teach the group how to measure the orientation of tilted layers using Brunton compasses. The students also got an opportunity to examine a spectacularly exposed syncline. From Rainbow Basin the group traveled north across the Garlock Fault, out of the Mojave Desert, and into the high desert of Owens Valley. Here they were greeted with dramatic changes in vegetation, climate, topography and geology. Rather than extensive deserts with the scattered cholla cacti or sage, they now faced towering mountains to their east and west. Seeing Mt. Whitney at 14,494 feet while standing in Owens Valley at only 3,000 feet was overwhelming to those people used to the gentle topography of Ohio. Traveling up the length of the valley also provided an opportunity to discuss issues related to water usage, because it is here that the Water Authority of Los Angeles purchased land and diverted streams running down from the Sierra Nevada to the agricultural lands of the Great Valley. The most obvious "scar" of this diversion is the Owens Lake where the group observed the salt flats that are the only remnant of the lake. In addition to Owens Lake, the southern portion of Owens Valley revealed to the students spectacular spheroidal weathering in the Alabama Hills, a fault scarp produced by a massive earthquake in the 1880's, gigantic alluvial fans constructed of boulders and gravels eroded from the Sierra Nevada, and a spectacular sunrise on the Sierran Front from our camp on the alluvial fan near the base of Mt. Whitney.
After a brief soak in a hot spring at the northern end of the Big Pine volcanic field, the group continued north to the alpine country near Long Valley and the Mono Basin. The dominant geologic feature in this area is the Long Valley Caldera, where a cataclysmic eruption 700,000 years ago buried the countryside under several hundred meters of hot volcanic ash. The group not only discovered the internal nature of such ash flow deposits, called welded ash flow tuffs or ignimbrites, but they also climbed on some of the subsequent lava flows from the still active granitic magma chamber, including the 600 year old obsidian dome called Panum Crater. Next stop in the Mono Basin was Mono Lake where hydrothermal waters rising through the bottom of lake, both today and in the past, have deposited towers of tufa, some as high as thirty feet! One final stop in the Long Valley/Mono Basin area was at Convict Lake where Dr. Greene described the geology of a stunning cliff face where he studied the geology of the country rocks intruded by the Sierra Nevada batholith.
From the northern end of Owens Valley, the group traveled south and east to Death Valley. On the way, the group stopped for lunch at an overlook into Panamint Valley where they saw dust devils on the playa, low flying F-18 fighter jets, and a normal-faulted sequence of Phanerozoic strata. Before descending into Death Valley, the group drove to Augereberry Point for a view across the Valley to the Black Mountains and the Funeral Mountains. Those students that opened their water bottles at Augereberry Point were surprised to find them crushed by the increased air pressure below sea level in the valley. The group's campsite for the next two nights was located in a narrow canyon carved into Quaternary lake deposits on the east side of the valley, affording excellent views of the sunsets. After a full day of examining the many geological features unique to this tectonically active rift basin, the group ascended from the morbid depths of Death Valley into the festering cesspool that is Las Vegas. On the way, the group visited Red Rocks State Park, where the group observed spectacular cross-bedded sandstones, and Hoover Dam where the group became diluted by droves of tourists.
Nights during the trip were spent camping in sites maintained by the Bureau of Land Management, the State of California, or the National Park Service. The weather was perfect the whole time; cloudless skies and temperatures that never dipped below 50 degrees. Given the mild temperatures, the fearless campers were content to sleep in their sleeping bags under the stars every night. The group would arrive in a campsite around five in the afternoon and be set up within an hour, leaving enough daylight for playing Frisbee or hacky-sack, or simply enjoying the awesome scenery.
Meals were wonderful. Breakfasts included hot and cold cereal, bagels, and fruit. Sandwiches of lunch meats and cheese or peanut butter and jelly formed the mainstay of lunches. In addition to the usual condiments, the group was treated to an amazing array of sprouts - including alfalfa, broccoli, radish, onion, and garlic. Dinners were cooked in camp by groups of four students who would prepare, cook, and serve dinner on their designated nights. Teamwork was never a problem and everything always went smoothly. The students were surprised that food cooked in the middle of a desert away from the comforts of home could taste so good, but meals of stew over cous cous, enchiladas, chili, and grilled chicken kabobs did just that. The students were directly involved in the logistics of the trip. Individuals were appointed 'czars' and 'czarinas' of various tasks. For example, one student made sure that the group always had enough water, while other students were in charge of storing food and supplies, keeping the vans clean, and cleaning the campsites. These responsibilities gave the students a sense of ownership of the trip that bonded the group.
The trip was educational, exciting, and fun. Students saw a wide variety of both active and ancient geological features not exposed in Ohio. This was a great trip, and one that should definitely be repeated in the future.