Mount St. Helens Triggers Aviation Warnings as Ash Reaches 12,000 Feet

Mount St. Helens, the site of one of the deadliest volcanic eruptions in U.S. history, has triggered urgent aviation warnings after a significant cloud of volcanic ash was detected billowing into the skies.

A SIGMET, a critical aviation weather alert, was issued late Thursday and extended into early Friday. Satellite imagery and U.S. Geological Survey (USGS) webcams captured a plume of ash drifting northwest of the volcano, reaching an altitude of approximately 12,000 feet above sea level.

This development raised concerns about potential renewed volcanic activity at the infamous peak, located south of Seattle in Washington State. However, officials were quick to clarify that the ash cloud was not the result of a recent eruption. Instead, powerful winds associated with a high-pressure system over the Pacific Northwest had swept up old volcanic ash from the ground.

"This phenomenon is not the result of recent volcanic activity and occurs during times of high winds and dry snow-free conditions in the Mount St Helens region," the USGS stated. "No eruption is in progress, and Mount St Helens remains at Aviation Color Code Green and Volcano Alert Level Normal."

Despite the lack of an active eruption, the suspended volcanic ash is considered hazardous to aircraft. The jagged particles of rock and volcanic glass can cause severe damage to jet engines, potentially leading to a complete loss of power. The ash also poses risks to human health, irritating eyes and lungs, reducing visibility, and potentially damaging machinery.

The Cascades Volcano Observatory issued an official aviation notice on Thursday afternoon after observing the ash plume. A subsequent advisory and the SIGMET warning were put in place to alert pilots to the hazardous conditions.

Mount St. Helens last experienced a catastrophic eruption on May 18, 1980. That event sent a plume of ash 2.5 miles into the sky, killed 57 people, and destroyed over 200 homes, earning it the grim moniker of America's deadliest volcano. The 1980 eruption caused widespread disruption, with ash falling like snow across multiple states and leading to the cancellation of more than 1,000 flights. Highways were closed for weeks, and hundreds of miles of railroad track operations were stalled by destructive mudflows.

In recent months, Mount St. Helens has shown increased seismic activity. The USGS detected 350 earthquakes over a five-month period, most of which were less than magnitude 1.0 and too small to be felt. The largest recorded quake in this period was a magnitude 2.0 on May 31, 2024. Scientists noted that specialized equipment had detected magma flowing through chambers deep underground, a process known as recharge, which is contributing to the increased seismicity.

While short-term increases in earthquake rates are common at Mount St. Helens and have occurred multiple times since its last eruption ended in 2008, the recent sequences represent the largest short-term increase in earthquake rates since then. However, historical data shows that similar periods of elevated seismicity in the past did not directly trigger a major eruption. The USGS has reported no significant changes in other monitoring parameters, such as ground deformation or gas emissions, indicating no immediate increase in hazards beyond the resuspension of ash.