Idaho Geologic Survey maps more than rocks
They direct, explain and quantify — although most people don’t use them every day, maps are an integral tool in navigating the world.
National Geologic Map Day is a day set aside by the U.S. Geologic Survey to bring attention to geologic mapping and to showcase some of the work done by state Geological Surveys.
Ed Ratchford, director of the Idaho Geologic Survey, said each state has the discretion to choose a map for Map Day and Idaho likes to diversify the map each year.
“It’s very arbitrary, but we like to show a mix of the different types of provinces and geologic terrains that occur throughout the state,” he said. “We don’t want to continue to show you geologic maps from the same area all the time.”
Ratchford said the IGS choice this year is the wilderness area around the University of Idaho’s Taylor Ranch.
Reed Lewis, one of two geologists who authored the map, said the remoteness of the area made it difficult to chart. He said he and Dave Stewart, his co-author, spent more than half of the summers between 1995 and 2010 intermittently mapping the geologic features of the area.
“(Stewart) comes up in the summers and does geologic mapping for us,” Lewis said. “Over this period, then, he basically stitched together this geologic story of old rocks, faulting, young rocks, so on and so forth.”
Lewis said the map itself has the same type of features as nearly all geologic maps. It shows the distribution of different types of rock found in the area, fault lines running through the rock formations and a correlation chart, which is a time chart showing the various ages of the rocks.
He said the time charts are often easier for non-geologists to understand than the map itself.
“Basically, if you were to drill to depth in those areas, this is what we speculate you would find,” Lewis said. “Obviously, there’s a certain amount of guess work that goes into that, but that’s basically gives you an idea of what we think is going on.”
Lewis said there are several groups that use the maps, including mining companies that are interested in locating mineralized faults for potential mine sites, engineers that use the maps as a resource to plan structures and geology enthusiasts who are interested in Idaho’s geologic history.
Ratchford said the survey also collects information of mineral resources, oil and gas potential and geologic hazards like seismicity and landslides.
“As the state geologist, my job is to oversee the agency, to make sure that we are following our mission statement and we’re providing high-quality geologic mapping service to citizens, because we are a state agency,” he said.
Ratchford said the public is welcome to come visit the IGS office, although it is only open on Tuesdays and Fridays.
“We have a lot of geologic resources here, we’ve got a trained staff here to answer people’s questions about the geology within the state, or specific questions about an area that they’re interested in,” he said.
He said people can buy maps from the survey in their office, or view them on the survey’s website.
Daphne Jackson can be reached at [email protected]