Map of Yellowstone National Park showing recent swarm earthquakes in red, previous swarms from 1995-2009 in green, and volcanic vents with yellow stars. Caldera boundaries are shown in orange. Mallard Lake Resurgent dome, to the southwest, and Sourcreek Resurgent dome, to the northeast, are shown with yellow lines. The histogram at the top right shows the number of earthquakes per day from January 15 to February 5. Image by Jamie Farrell and Robert B. Smith (University of Utah), data from the University of Utah Seismograph Stations.