Arlington, Va. — When President Thomas Jefferson sent Lewis and Clark across the nation to explore the American West in 1803, the world knew little about western America. The discoveries the expedition made, many unprecedented, led us to appreciate our nation's natural resources, settle the West, and eventually, to establish national parks.
Now, exactly two centuries later, the National Science Foundation (NSF) has funded a latter-day Lewis and Clark expedition: EarthScope, a scientific exploration of the structure and evolution of the North American continent, and the physical processes controlling its earthquakes and volcanic eruptions. This time, however, instead of toting sextants and compasses to map the surface, scientists will bring seismometers, state-of-the-art drilling equipment, satellites and GPS receivers to map Earth's interior.
"Studies of geology have enabled us to infer the processes that shaped and continue to shape our continent," said Margaret Leinen, assistant director of NSF for geosciences. "Now technology can allow us to watch these processes on a human time scale, one as short as an academic school year. EarthScope will not only help us understand how the North American continent formed, it will make possible the mapping of the continent's changing structure."
The EarthScope infrastructure will be constructed over the next five years. "The effort capitalizes on new broadband seismic sensors, developments in GPS technologies, reduced telecommunication costs, and a data distribution infrastructure now in place," said scientist Gregory van der Vink, director of the EarthScope project. "EarthScope will collect and integrate scientific information derived from geology, seismology, remote sensing and geodesy, the science of measuring Earth's surface features."
An array of 400 seismometers will form a moving net of geologic sensors across the contiguous 48 states and Alaska, occupying 2,000 locations over 10 years to assemble an image of the internal structure of the continent and underlying mantle from "crust to core." The array, to be constructed by the Incorporated Research Institutions for Seismology (IRIS), will investigate earthquakes, volcanoes, and active mountain-building in Alaska and the West. In the eastern United States, the array will study the early development and roots of our continent, imaging the deep Earth for clues about the origin of the magnetic field and the driving mechanisms of plate tectonics.
"EarthScope will create some of the most exciting science of our generation," said Jim Whitcomb, section head in NSF's division of earth sciences, which funded EarthScope. "In practical terms, our improved knowledge of North American continent dynamics will greatly advance efforts to reduce earthquake hazards."
A network of GPS receivers, to be constructed by the University NAVSTAR Consortium, Inc. (UNAVCO, Inc.), will continuously record the deformation of the earth's surface. Sensitive bore-hole strain meters will measure changes in stress along the plate boundary of the western United States and Alaska, explained van der Vink. "These sensors will measure how the North American crust is deforming, how earthquakes start and how magma flows beneath active volcanoes."
EarthScope will also work with NASA to develop a Synthetic Aperture Radar satellite. These data will map changes in Earth's surface before, during and after major earthquakes and volcanic eruptions.
An observatory, to be constructed by Stanford University in collaboration with the U.S. Geological Survey (USGS), that will be placed four kilometers deep into the San Andreas fault will provide the first opportunity to determine directly the conditions under which earthquakes occur, to collect fault rocks and fluids for laboratory study and to monitor continuously an active fault zone at depth.
Data from all EarthScope components will be integrated to produce models of continental structure and dynamics, and to determine how those structures evolve, said Whitcomb. "The seismological and drilling components will yield detailed images of Earth below the surface," he said, "while the GPS, strain meter and radar images will allow us to view changes in those structures through time."
For the first time, concluded van der Vink, "we are no longer limited to inferring plate tectonics from the geologic record. EarthScope will allow us to observe these geologic processes in real time."
All data from EarthScope will be available to the public in real-time to maximize participation from the scientific community and to provide on-going educational opportunities for students of all ages.
EarthScope is a multi-agency, national program with important roles played by NSF, USGS, NASA, and other federal agencies. Partnerships are also being developed with state agencies, regional seismic networks, organizations in Mexico and Canada, and the International Continental Drilling Program (ICDP).
Lewis and Clark likely wouldn't believe where 200 years has taken us.
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