Over 120 Small Quakes Near Mount St. Helens Signal Future Volcanic Eruption

Scientists are taking a closer look in the recent swarms of over 120 small quakes that occurred near Mount St. Helens in late November, watching out for any indicators of future explosions.  Photo: Richard Bowen

Scientists are taking a closer look in the recent swarms of over 120 small quakes that occurred near Mount St. Helens in late November, watching out for any indicators of future explosions.

According to reports, there is nothing alarming about the recent series of small quakes. It all happened between one and two miles below the surface and most registered at magnitude 0.3 or less, with magnitude 0.5 as the largest. The quakes are so weak that it can be barely felt by someone standing directly on their epicenter.
"Each of these little earthquakes is a clue and a reminder we are marching toward an eruption someday," said Weston Thelen, a U.S. Geological Survey seismologist with the Cascades Volcano Observatory in Vancouver, in a report from The Columbian.

The scientists believe that the small quakes were caused gases and fluids released by the magma coming up into the volcano's internal system and are stored. These gases and fluids pressurized and lubricates crack as it travels, causing the small quakes.

Despite the lack of data pertaining any anomalous gases or increase in ground inflation, scientists believe that Mt. St. Helens is slowly repressurizing and is inflating subtly. Similar series of small quakes were observed during the recharge period of Mt. St. Helens between the 1986 and 2004 eruption. The swarms of quakes halted shortly during the 2008 eruption but continued shortly after the eruption. Since then, swarms of small quakes have been detected in the volcano, with the most recent clusters detected in March through May this year.

Due to the weak tremors produced by the quakes, scientists required the assistance of sensitive seismometers stationed around the mountain. By measuring these small quakes, scientists could have a better understanding about the inner workings of the volcano. Measuring how the speed of the seismic waves change as they move through the earth could also provide a clearer insight on rock densities and the location of magma chambers.


The above post is reprinted from Materials provided The Columbian.