The geysers and hot-springs of Yellowstone are produced by what’s called a magma plume under the Earth’s surface. Water in the Earth’s crust is heated by this plume causing the hydrothermal activity we see on the surface. Scientists believe that the magma plume beneath Yellowstone may reach over 600 miles into the Earth. It is this plume which could potentially erupt.
There have been three supereruptions in Yellowstone’s history, the last being about 640,000 years ago. In 2014, USGS scientists released a report where they modeled the outcome of a potential Yellowstone eruption. The results would be devastating, not just for the United States, but for the rest of the world as well.
The scientists modeling the eruption calculated the eruption time as lasting from days to months. Larger eruptions like the 1912 Novarupta eruption in Alaska lasted roughly 52 hours. But scientists have suggested that smaller eruptions have lasted from weeks to months. The Eyjafjallajökull eruption in Iceland in 2010 ejected magma for 59 days.
The USGS study notes that most of the continental United States would be covered in ash for an extended period of time. The coastal regions, where the majority of the US population resides, could be covered in several centimeters of ash and up to several feet in some places. Ash would contaminate water supplies, kill off crops and livestock, and short out electrical equipment. Globally the ash could produce a 1 degree Celsius cooling effect.
No. Despite the extensive coverage of the recent earthquake swarm, scientists at the Yellowstone Volcano Observatory say that there are no signs that an eruption may be pending. Being a volcanic region, the Yellowstone area is prone to frequent quakes. A significantly large earthquake in just the right place may trigger an eruption but even that is not guaranteed. The USGS study notes that large eruptions, though not necessarily supereruptions, tend to occur once every 100,000 years. The last Yellowstone eruption was 70,000 years ago so we’ve still got 30,000 to go.