BRANDON HANSEN / KCHW NEWS

Mount Rainier is not erupting.

… but there has been a flurry of seismic activity reported early Tuesday morning.

The U.S. Geological Survey’s Cascades Volcano Observatory confirmed that a swarm of small earthquakes began around 1:30 a.m. on July 9 beneath Mount Rainier. These hundreds of tiny quakes occurred several times per minute, with depths ranging between 1.2 and 3.7 miles below the summit. The largest was a magnitude 1.7, which is too small to be felt at the surface and is business as usual for the volcano.

According to the USGS, Mount Rainier experiences more than 100 earthquakes every year, averaging about nine per month. Earthquake swarms, like the one now underway, happen about once or twice a year — though this one is more active than usual.

Seismologists say the likely culprit is superheated groundwater or volcanic gases moving through existing faults deep below the mountain. These hot fluids can trigger tiny slips in the rock, which we detect as earthquakes.

The current activity isn’t unusual, but scientists are keeping a close eye on it. If earthquakes begin occurring closer to the surface, or if the ground begins to swell or vent gas, that could indicate that magma is on the move.

But for now, all systems remain calm. Monitoring instruments show no signs of ground deformation, and infrasound sensors — which can pick up low-frequency volcanic sounds — aren’t detecting anything out of the ordinary.

For perspective, the last significant earthquake swarm at Rainier happened in 2009 and included more than 1,000 quakes over three days. That episode ended without incident.

As of Tuesday, the USGS alert level for Mount Rainier remains at “Green / Normal.” In other words, no need to panic — just another day living next to one of the Pacific Northwest’s most iconic and closely-watched volcanoes.