Senior Airman Marina Martinez and Rachel Silverberg, 90th Force Support Squadron, take a selfie with a geyser in the background in Yellowstone National Park, Wyo., July 4, 2015. Martinez and Silverberg were participants of an F.E. Warren Air Force Base Outdoor Recreation trip exploring Yellowstone and Grand Teton National Park for the Fourth of July weekend. (U.S. Air Force photo by Lan Kim)