Earthquakes (red dots) and young faults (black lines) in greater Yellowstone area. Earthquake epicenters are clustered due to the frequent occurence of earthquake swarms. A high number of faults leads, most of them not related to volcanism, lead to a high earthquake hazard. Multiple strong, tectonic quakes have happened in the last decades, including quakes larger than magnitude 7. The last small volcanic eruption happened 3000 years ago.
The circular-shaped faults indicate the calderas created during the last major eruptions 640000 years ago and 1,3 mio years ago: The younger and bigger right in the center of the map and the older, smaller to the southwest.