Located in Katmai National Park, Alaska, this valley was transformed by the largest volcanic eruption of the 20th century. The eruption of Novarupta buried the landscape in nearly 700 feet of hot ash. As groundwater came into contact with the heat, it turned into steam, bursting through the surface via thousands of fumaroles. These vents emitted gases and high-pressure steam for decades. Geographically, it represents a classic “ignimbrite” landscape. Although the “smokes” have largely diminished as the ash flow reached thermal equilibrium, the valley remains a spectacular lunar-like terrain used by scientists to understand volcanic gas emissions.