On a chilly morning, Fred Jenkins strides across the West Garfield County landfill. Past hunkered-down dumptrucks and mountains of appliances alive with chattering magpies, he stops at what appears to be a tripodal alien spore.
It's a global positioning system (GPS) monument that Jenkins helped install in this sage-speckled swath of western Colorado five years ago. With practiced hands, he replaces the monument's antenna and receiver box, which have stopped transmitting data. "Probably a lightning strike," he muses, scratching his cinnamon-sugar goatee.
Dubbed P031, the station is one in an array of more than 1,100, scattered around the country from wilderness peaks to airports to prison yards. Together, they comprise the National Science Foundation's nine-year-old Plate Boundary Observatory (PBO), a project overseen by the nonprofit UNAVCO, which facilitates geoscience research in the U.S. The PBO is the second-largest global positioning network in the world, right behind Japan's GPS Earth Observation Network.
It's also one of the largest efforts to survey and map the Western U.S. since the Lewis and Clark expedition, says David Kasmer, a PBO field engineer working the Eastern Sierra and the Rocky Mountain states. "Except that we are focused on mapping the interior of the Earth, its inner workings. It's the evolution of surveying."
PBO stations are mostly concentrated in geologically fitful parts of the West and along the North American and Pacific plates' active boundary. The stations — drilled into solid bedrock that lies anywhere from one to 12 metres below the surface — measure motion and deformation of the Earth's crust. Eight keep tabs on the Yellowstone Caldera, for example. And when Alaska's Augustine Volcano erupted in 2006, its five PBO stations transmitted information on vertical and horizontal ground motion from the volcano's flank right up until two were swallowed by an ash flow. Scientists use the real-time data — accurate to the millimetre — to understand earthquakes and volcanic cycles. The work also informs the development of early warning systems.
Though high-tech, the system is built on logistical gruntwork. Because the stations need unobstructed views of the satellites to which they "talk," and because buildings and radio interference can scramble station signals, most are seriously far-flung.
Indeed, the stations require a maintenance crew of engineers as rough and tumble as the landscapes in which they work.
"There aren't too many people like (the PBO engineers), that's for sure," says Jenkins, who's used to troubleshooting complex machinery in tough conditions. After joining the Coast Guard in 1970 ("when ships were wood and men were steel") to bone up on diesel engine mechanics, he was eventually stationed as an engineman on a small ship that tended buoys and channel markers in Cape Hatteras off the North Carolina coast. "Operating any ship is an inherently risky activity," says Jenkins, "but a buoy tender offers up all sorts of unique opportunities for calamity" — fingers smashed under wire ropes, severe weather, crewmates falling overboard.
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