Editor's note: The following piece was written by first-year students and members of Terrascope Rin Yunis, Emily Shorin and Judy Pu. The students recently returned from a trip to the American Southwest, where they and their classmates visited active mines to learn about extraction and use of strategic minerals including lithium and the rare earth elements. The Terrascope program sponsors an annual field trip over spring break focused on the year's theme.
While many students either escaped to a beach or went home to see family, a group of 24 MIT undergraduates and 10 adult mentors headed to two states in the American Southwest for spring break. The group comprised of first-year students who had been part of the fall Terrascope class 12.000 (known as Mission 2016), undergraduate teaching assistants, graduate students, professors, Terrascope staff and two alumni mentors who had advised the class.
The annual trip is part of the full Terrascope learning experience; an attempt to put into context the problem that the students had worked to solve in the fall. The subject of this year’s class was the “Future of Strategic Natural Resources,” which addressed the limited supply and increasing demand for resources such as rare earth elements, phosphorus and lithium that are needed for the production of many modern technologies and consumer goods. To see where the minerals they had studied in Mission 2016 came from, the group visited a series of mines in California and Nevada, including the Rockwood Lithium mine, Searles Valley Minerals Trona Facility, Rio Tinto borax mine, Oceanview Pegmatite Mine and Simplot silica mine.
Rockwood and Searles Valley are both in-situ mines that pump brine from underground aquifers. While Rockwood Lithium uses evaporation ponds to concentrate and then precipitate out their products, Searles Valley is more industrialized and uses a vast system of pipes, pumps and facilities where the effluent is processed. By contrast, Rio Tinto is an open-pit mine, mining minerals that are part of 20-million-year-old lake deposits. Simplot's silica mine is also open-pit and produces high quality silica sand, mostly used in glass production.
The Oceanview mine stood out from the rest as an underground gem mine notable for the size of the minerals in the rocks. Several of their giant gems are now on display in museums worldwide, including the Smithsonian Institution in Washington, D.C. A brief stop was made at Mountain Pass, a rare earth mine currently operated by Molycorp that is the location of the largest rare earth deposit in the United States.
At Death Valley and Zion National Park, the focus was on the area’s geology. Death Valley is a perfect example of Nevada's basin and range system, the largest of its kind in the world. A basin and range system occurs along dipping faults, where the crust is extended by as much as 100 percent to form low basins. Volcanic activity occurs due to the thinned lithosphere and crust. Cinder cones formed by basaltic magma eruptions are a common feature. Death Valley is the lowest of all these valleys (basins) at 282 feet below sea level, although an 11,000-foot peak hovers above it.
Rockwood Lithium is located in Clayton Valley, another basin. Dwight Bradley, a United Stages Geological Survey (USGS) geologist who accompanied the group there, has examined why lithium is concentrated only in the Clayton Valley area and a few particular closed playa lakes. The current theory involves tectonic activity, which would facilitate the migration of lithium and other minerals from hydrothermal fluids deeper in the earth. Many of the outcrops visited on the trip had obvious signs of tectonic activity, a result of the proximity to the Pacific and North American plate boundary.
Zion National Park shows evidence of tectonic activity, but with completely different results. The park is part of the Grand Staircase, an exposure of a block of layered sedimentary rocks pushed up at intervals between the Grand Canyon, Zion and Bryce Canyon National Park. Zion is in the middle, with its lowest (oldest) layer being the top layer of the Grand Canyon, and Zion's topmost rock layer is Bryce's bottom layer.
The canyon, carved by the river still flowing at its bottom, has many rock layers, some containing dinosaur foot prints, petrified wood and petroglyphs — markers that help geologists visualize and reconstruct the history of the zone. In some areas, huge stretches of sandstone with cross-stratification are exposed, recording the migration of ancient dunes and wind directions, and providing onlookers with a glimpse of past climates. Both of these parks are stunning examples of the tectonic forces shaping the Southwest, creating the mineral deposits exploited by mines in the area as well as their natural beauty.
The group visited Hoover Dam and water treatment facilities in Las Vegas and Henderson, Nev., to see the full cycle of water conservation and use in the Southwest. Recycling and distribution rights are highly contested issues and vital for survival in the desert. Ninety percent of water used in Las Vegas is recycled. However, more and more water is being used as the population grows, and the Colorado River alone cannot provide all that is needed. Las Vegas is looking elsewhere for rivers to divert and for vast, still untapped aquifers to the north that it can exploit.
The demand for water in the southwestern United States has been going on for a long time. A vivid example of this expansion is Owen's Lake, located near Death Valley, which once received all the water from the Owens River before it was diverted to fuel a growing Los Angeles in 1913. Today the lake has dried up and become a playa, but in the past the Owens River valley was rich agricultural land with large farms and orchards, as well as a number of nearby mines. Water and its careful allotment and use in this part of the Southwest is an example of a scarce and essential resource being managed in as sustainable a manner possible, similar to the sustainable approach Mission 2016 attempted to provide for a variety of scarce element resources.
The groups’ visit to Hoover Dam was one of the last stops on the trip. The building of the dam — an incredible feat of civil engineering that uses the Colorado River as a source of hydroelectric power — created Lake Mead, which flooded the Colorado River canyon, including settlements and towns that had formed along the river. Receding lake levels due to prolonged drought, a great source of concern, have exposed some ghost towns previously covered by Lake Mead.
This trip could not have been better engineered to supplement the Terrascope curriculum and give freshmen a hands-on learning experience about the fragility of many of the world’s natural resources. Back at MIT, these students can apply their new perspective to their studies, in particularly those students who are in the two Terrascope spring programs: Terrascope Radio and Communicating Complex Environmental Issues: Building Solutions and Communicating Ideas. Although students may have thought they had already learned about these areas, everyone took away something new from the trip. As Ana Vasquez put it: “Soon we will leave, but the Southwest will keep our steady gazes, questions and echoing steps.”