There's a whole lot of shaking going on underneath the most active volcano in the lower 48 states, according to the US Geological Survey. The USGS says that while there's no sign that Mount St. Helens is going to blow its top any time soon, there has been a swarm of low-magnitude earthquakes at the volcano in Washington state since the start of the year and the quakes have increased in frequency to almost 40 a week, CNN reports. "The magma chamber is likely imparting its own stresses on the crust around and above it as the system slowly recharges," the USGS says. "The pressure drives fluids through cracks, producing the small quakes." The quakes are deep and of very small magnitude—the largest measured was just 1.2—meaning they haven't been felt at the surface.
The quakes are a sign that the volcano is still alive and will erupt again someday, but the next eruption is probably "years to decades down the road," Seth Moran, the scientist in charge at the USGS Cascades Volcano Observatory in Vancouver, tells LiveScience. Washington. Scientists haven't detected changes in gas emissions or other danger signs at the volcano, where a May 18, 1980 eruption killed 57 people. That eruption was preceded by more than 10,000 small quakes. How long it will take to recharge before the next eruption, and what could trigger it, is one of the "big questions of volcanology," Wired notes. (These Australian scientists were looking for lobsters when they found four undersea volcanoes.)