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The Columbia River winds its way through Washington State before becoming the border with Oregon. This location is an overlook along I-90.

The Columbia River winds its way through Washington State before becoming the border with Oregon. This location is an overlook along I-90. The town of Vantage can be seen on the righthand side where I-90 crosses the Columbia.

The Columbia River winds its way through Washington State before becoming the border with Oregon. Along its banks can be found sagebrush.

The Columbia River winds its way through Washington State before becoming the border with Oregon. Along its banks can be found sagebrush.

Prairie dogs live in subterranean burrows to escape predators. These burrows interconnect to form prairie dog towns.

Devils Tower is a laccolith in the Black Hills of Wyoming. A laccolith forms when molten magma forces its way into a rock formation, then cools and hardens. As the surrounding rock erodes away, the hardened former magma remains.

Devils Tower is a laccolith in the Black Hills of Wyoming. A laccolith forms when molten magma forces its way into a rock formation, then cools and hardens. As the surrounding rock erodes away, the hardened former magma remains.

Devils Tower is a laccolith in the Black Hills of Wyoming. A laccolith forms when molten magma forces its way into a rock formation, then cools and hardens. As the surrounding rock erodes away, the hardened former magma remains.

Devils Tower is a laccolith in the Black Hills of Wyoming. A laccolith forms when molten magma forces its way into a rock formation, then cools and hardens. As the surrounding rock erodes away, the hardened former magma remains.

Devils Tower is a laccolith in the Black Hills of Wyoming. A laccolith forms when molten magma forces its way into a rock formation, then cools and hardens. As the surrounding rock erodes away, the hardened former magma remains.

Prairie dogs forage in the grasslands at the base of Devils Tower National Monument in Wyoming.

Several Native tribes consider Devils Tower and its surrounding area to be a sacred site. Members of these tribes sometimes leave prayer bundles or flags tied to trees.

Several Native tribes consider Devils Tower and its surrounding area to be a sacred site. Members of these tribes sometimes leave prayer bundles or flags tied to trees.

USGS researcher Jonathan Caine measures vein orientation at an outcrop of late Cretaceous pluton in Lake Clark National Park.

USGS scientists Erin Todd and Jonathan Caine wait for a helicopter pickup at a geologic mapping and sampling station high in the Neacola Mountains, Alaska.

The Big Sioux River, as it passes through the city of Sioux Falls, has a beautiful waterfall for which the town is named.

The Big Sioux River, as it passes through the city of Sioux Falls, has a beautiful waterfall for which the town is named.

The Big Sioux River, as it passes through the city of Sioux Falls, has a beautiful waterfall for which the town is named.

The Big Sioux River, as it passes through the city of Sioux Falls, has a beautiful waterfall for which the town is named.

The Big Sioux River, as it passes through the city of Sioux Falls, has a beautiful waterfall for which the town is named.

The Big Sioux River, as it passes through the city of Sioux Falls, has a beautiful waterfall for which the town is named.