Overview
- The earthquake swarm began at 1:29 a.m. PT on July 8 and continues through July 10 at reduced intensity after an initial surge of hundreds of quakes.
- The tremors, located 2–6 km beneath the summit, peaked at magnitude 1.7 and remain too minor to produce surface effects.
- Dense networks of seismometers, infrasound sensors, GPS and webcams detect no ground deformation or unusual gas emissions at the volcano.
- Cascade Volcano Observatory scientists identify circulating hydrothermal fluids as the most likely cause, ruling out magma intrusion.
- Although the largest swarm since 2009, similar episodes occur once or twice a year at Mount Rainier and do not signal an imminent eruption.