USGS geologist collects a sample from a potential newly recognized lava flow along the Gibbon River, Yellowstone National Park
USGS geologist collects a sample from a potential newly recognized lava flow along the Gibbon River, Yellowstone National ParkUSGS geologist Mark Stelten collects a sample of what is potentially a newly recognized lava flow exposed along the Gibbon River. USGS photo by Nicole Thomas, September 2025.