when was the last time a volcano erupted in utah
1980 eruption of Mount St. Helens On May 18, 1980, a major volcanic eruption occurred at Mount St. Helens, a volcano located in Skamania County, in the State of Washington. The eruption (a VEI 5 event) was the most significant volcanic eruption to occur in the contiguous 48 U.S. states since the much smaller 1915 eruption of Lassen Peak in California.[1] It has often been declared as the most disastrous volcanic eruption in U.S. history. The eruption was preceded by a two-month series of earthquakes and steam-venting episodes, caused by an injection of magma at shallow depth below the volcano that created a large bulge and a fracture system on the mountain's north slope.
Yellowstone Caldera Non-explosive eruptions of lava and less-violent explosive eruptions have occurred in and near the Yellowstone caldera since the last supereruption.[13][14] The most recent lava flow occurred about 70,000 years ago, while a violent eruption excavated the West Thumb of Lake Yellowstone around 150,000 years ago. Smaller steam explosions occur as well: an explosion 13,800 years ago left a 5 km (3.1 mi) diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera).[15][3] Currently, volcanic activity is exhibited via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser, plus recorded ground-swelling indicating ongoing inflation of the underlying magma chamber.