Eruptions of smoke and steam continued at Mount St. Helens over the weekend and into Monday. On Saturday, seismologists raised the Volcano Alert to the highest level after recording longer sustained "harmonic vibration" earthquakes within the volcano -- a sign that an impending eruption is likely.
"We continue to be concerned that additional steam-and-ash eruptions could occur at any time," said U.S. Geological Survey officials in Monday's newest Volcano Alert release. "The principal hazard from these types of events is for ash reaching altitudes that could affect aviation. If the current unrest continues there is also an increased probability of larger magnitude and more ash-rich eruptions."
The Volcano Alert also stated that USGS scientists "believe that there is a significantly increased probability that gas-rich magma is moving toward the surface." Yet the scientists are not able to predict when or how large a possible eruption could be.
Some ash has been detected in the smoke after the steam eruptions. Meteorologists with the National Oceanic and Atmospheric Administration (NOAA) continue to work with USGS officials on determining wind patterns in the even a more sizeable ash cloud.
According to a Monday's release, "wind forecasts from the NOAA, combined with eruption models show winds today will be from the east and southeast and any ash clouds would drift to the west and northwest."
Over the weekend, some nearby residents evacuated as a precaution, yet many tourists and volcano-enthusiasts lined up along roads near the volcano hoping to catch a glimpse of the activity.
The USGS scientists first alerted the public to the new seismic activity at Mount St. Helens last Sunday with the first 'Notice of Volcanic Unrest' released in 18 years. Then they released the ‘Volcano Advisory’ last Wednesday due to significant increases in seismic activity. At that point, the scientists were saying the chance of an explosion was around 70%.
Wednesday's USGS release happened because the earthquakes had been occurring at about four per minute – with some being as strong as a magnitude 2.5 – prompting USGS officials to say that explosions from the Mount St. Helens’ lava dome could occur suddenly and without warning. As the week continued, the earthquake became stronger and more frequent.
According to USGS seismologist Seth Moran, explosions at Mount St. Helens could produce 'ballistic projectiles' - meaning high- and fast-flying rocks and debris. The explosions could also produce ash plumes reaching thousands of miles high above the lava dome. Similar explosions have happened before, with the last time being 15 years ago.
The quakes can also cause landslides. With such possible hazards, the U.S. Forest Service has closed off most of the mountain and hiking trails.
Seismologists say the site has been subject to swarms of small earthquakes in the past, yet this time is different. "This one has lasted longer and has been more intense than previous swarms," said Moran.
Mount St. Helens became a familiar name after its major 1980 eruption, which killed 57 people and permanently changed the mountain's geography. That eruption also destroyed entire forests and spewed ash and rocks hundreds of miles away.
Scientists at the Cascades Volcano Observatory are continuing their monitoring in response to all the recent earthquake activity. New instruments are being set up around the volcano's dome, and researchers are constantly checking the area's atmospheric composition for magmatic gases.
Meanwhile, quakes shook another part of the West Coast last Tuesday. An earthquake measuring 6.0 on the Richter scale rattled central California. The quake’s epicenter was closest to the small town of Parkfield, labeled “the earthquake capital of California” due to its position directly on the San Andreas fault.
The State Highway Patrol reported one minor traffic incident due to boulders on the road, but there are no reports of damages or injuries. There were also numerous reported aftershocks measuring as strong as 4.0 felt throughout the region. Strong aftershocks were felt Wednesday morning as well.
The quake was felt from San Francisco to Los Angeles along a 350-mile stretch, according to the U.S. Geological Survey.
Parkfield is about 21 miles northeast of Paso Robles, where an earthquake killed two people in December.
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