The broad McDermitt Caldera is a prominent geologic feature in the Trout Creek Mountains. The oval-shaped caldera is a collapsed lava dome that straddles the Oregon-Nevada border on the eastern side of the range and south of the Oregon Canyon Mountains. It is about long and wide. The lava dome was created by volcanic eruptions in the early Miocene. A total of five large ash flows were produced along with a large rhyolite dome structure. The caldera formed when the dome collapsed about 16 million years ago. The caldera contains significant ore deposits, and mercury and uranium have been mined at eight or more sites in and around the caldera. Other areas in the caldera were mined for ores of antimony, cesium, and lithium.