Mount Adams Washington Volcano Update; Dramatic Jump in Earthquakes

Something unusual is occurring at Mount Adams, a glacier-covered active volcano situated in south-central Washington state. Over the last month, the rate of volcano-tectonic earthquakes beneath its surface has surged to an astonishing 180 times higher than normal levels. This is a significant shift for a volcano that has remained largely quiet for nearly a millennium.

Key Takeaways

• Seismic Activity: Earthquakes have increased dramatically, with six recorded in the last month.
• Historical Context: Mount Adams has been mostly inactive for the past 1,000 years.
• Potential Causes: Three main theories explain the recent seismic activity.
• Monitoring Efforts: New seismic stations are being added to track the situation.

Mount Adams typically experiences a volcanic tectonic earthquake about once every 2.5 years. However, in the last month alone, it has recorded six such earthquakes, ranging in magnitude from 0.85 to 1.95. While these numbers may seem low compared to more active volcanoes, they are significant for Mount Adams, which ranks near the bottom in terms of seismic activity among the Cascade Range volcanoes.

The earthquakes occurred between September 9th and September 28th, with the strongest quake striking at 6:30 AM on September 24th. These quakes were shallow, occurring at depths between 220 meters below sea level and 1,010 meters above sea level. Despite being the highest number of earthquakes recorded since monitoring began in 1982, experts believe these events are not directly related to magma movement.

Reasons for Low Magma Activity

1. Lack of Ground Deformation: No recent ground deformation has been detected, which is typically a sign of magmatic intrusion.
2. Location of Earthquakes: Five of the six earthquakes were centered in the western half of Mount Adams, while the magma chamber is primarily located beneath the eastern side.
3. Depth of Earthquakes: The earthquakes occurred at depths inconsistent with typical magma movement, with the deepest quake striking a mile above the modeled magma chamber.

Possible Causes of the Earthquakes

Given the unusual nature of these earthquakes, three main possibilities have been proposed:

1. Minor Magma Intrusion: Small amounts of magma may have intruded beneath Mount Adams, increasing heat in the hydrothermal system and leading to more earthquakes.
2. Increased Heatflow: The same increase in heat could occur without any new magma, affecting the hydrothermal system.
3. Landslide Creep: Although unlikely, the earthquakes could be a result of slow landslide movement on the western flank, which has a history of producing debris avalanches and lahars.

Historical Context of Mount Adams

While Mount Adams has been relatively inactive in the last 1,000 years, it has produced the third most volcanic eruptions during the entire Holocene epoch, with the last eruption occurring around the year 1000. This historical context is crucial for understanding the current seismic activity.

Monitoring and Future Implications

In response to the unusual seismic activity, the U.S. Geological Survey and Pacific Seismic Networks are tripling the number of seismic stations near Mount Adams by adding two temporary sensors. This increased monitoring will help scientists better understand the situation and assess any potential risks.

On a scale of 0 to 10 for volcanic unrest, the current activity at Mount Adams is rated as a 1. This rating reflects the potential for more undetected microearthquakes due to the limited seismic network in the area.

In conclusion, while the recent surge in seismic activity at Mount Adams is noteworthy, it does not currently indicate an imminent volcanic eruption. Continued monitoring will be essential to ensure the safety of nearby communities and to further our understanding of this intriguing volcano.