Yellowstone National Park has been seismically active for over two million years. Even to this day, the place is a dynamic geothermal hotspot.
Yellowstone National Park in the northwest corner of Wyoming is the oldest National Park in the United States and is certainly one of the most interesting volcanic sites in the world.
Almost the entire park of Yellowstone is sitting on an ancient and still active caldera. The caldera is covered by multiple stratified lava flows. The last lava flow occurred over 75,000 years ago. The area still remains seismically active with thousands of small earthquakes each year and geothermal venting through its geysers such as the venerable Old Faithful and boiling mud pots.
Yellowstone Sits Atop a Supervolcano
A supervolcano is a volcano that has produced unusually large eruptions in the past that are 8 in magnitude on the Volcanic Explosivity Index (VEI), as documented at Questions about Supervolcanoes by the United States Geological Survey. The caldera that forms most of Yellowstone is approximately 34 miles by 45 miles in area and was formed when a huge volcanic eruption collapsed the emptied magma chamber and created the depression.
Super eruptions have occurred at Yellowstone many times in the past, and at least one of the two million years ago was thousands of times more powerful than the eruption of Mount St. Helens as a comparison. A larger eruption over two million years ago left a gaping hole that was larger than the state of Rhode Island.
For most of the twentieth century, the caldera beneath Yellowstone was thought to be extinct until University geophysicist Bob Smith published his survey in 1979 that the ground beneath Yellowstone Lake was doming and forcing the lake levels to rise. Subsequent earthquake swarms in 1985 caused the dome to subside. There is no doubt now, though, that the ancient volcano is very much alive.
Earthquake Swarm at Yellowstone National Park
An earthquake swarm is a series of earthquakes that occur in a burst of activity in a relatively short period of time. An earthquake swarm was detected in the park and was one of the largest swarms ever recorded there. This is not an alarming development, however, as Yellowstone has experienced earthquake swarms many times before.
Interestingly, earthquakes as far away as Alaska have caused earthquake swarms in Yellowstone or have altered the action of hot springs and geysers for months after they occurred, per a study from the University of Utah.
The Deep Magma Chamber and the Movement Up and Down of the Caldera
With the aid of sound waves, the magma chamber plume underneath the park is thought to be about 400 miles deep. The caldera height is constantly in flux and is rising at the rate of about three inches a year which is higher than the historical norm.
Yellowstone is truly a geothermal hotspot and shows no signs of losing that status anytime in the foreseeable future.