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) lay