Mount St Helens triggers aviation warnings after winds whip up old volcanic ash 12,000 feet into the skies

Urgent aviation warnings were issued after a dangerous cloud of volcanic ash was detected billowing from Mount St Helens.

A SIGMET, a serious aviation weather alert, was issued late Thursday, lasting until early Friday, as satellite imagery and webcams captured a plume of ash drifting northwest of Washington State's notorious volcano, located south of Seattle.

The volcanic ash cloud rose as high as 12,000 feet above sea level, posing a potential hazard to aircraft flying through the area.

The warning raised fears of renewed volcanic activity at the site of one of America's deadliest eruptions.

Images from the US Geological Survey's (USGS) web cameras monitoring the volcano captured plumes of ash engulfing the formation, creating the impression that it had suddenly reawakened.

However, officials stressed that powerful winds had swept up old volcanic ash from the ground, creating a potential hazard for aircraft flying through the area.

Mount St Helens experienced a major eruption on May 18, 1980, sending a plume of ash 2.5 miles into the sky. 

A total of 57 people died, and more than 200 homes were destroyed, earning it the nickname America's deadliest volcano. 

A high-pressure weather system over the Pacific Northwest brought powerful winds sweeping across the Cascade Mountains, stirring up decades-old volcanic ash from Mount St Helens and sending it thousands of feet into the atmosphere. 

'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 agency explained.

'No eruption is in progress, and Mount St Helens remains at Aviation Color Code Green and Volcano Alert Level Normal. 

'Resuspended volcanic ash should be considered hazardous and could be damaging to aircraft and health.'

The Cascades Volcano Observatory issued an official aviation notice at 1.01pm local time Thursday after webcam footage showed ash reaching an estimated 12,000 feet above sea level and drifting northwest.

An updated volcanic ash advisory was given at 5.48pm. 

A separate SIGMET warning was in effect from 7.37pm until 11.36pm, alerting pilots to hazardous ash in the skies near Mount St Helens. 

Although no eruption was underway, experts warned that the airborne material could still threaten aircraft and human health.

Volcanic ash is particularly dangerous because it consists of tiny, jagged fragments of rock and volcanic glass rather than the soft residue produced by an ordinary fire. 

If sucked into a jet engine, the abrasive particles can cause serious damage and, in extreme circumstances, lead to a complete loss of engine power.

The particles can also irritate the eyes and lungs, reduce visibility and damage machinery, according to the USGS.

While the USGS assured the public that Mount St Helens is not erupting, the volcano gave the nation a scare in June 2024 when it began rumbling.

Scientists detected 350 earthquakes over five months. Most of these - more than 95 percent - have been less than magnitude 1.0 and are too small to be felt at the surface.

The largest quake felt at the volcano, located in southwestern Washington, about 50 miles northeast of Portland, Oregon, was a magnitude 2.0 on May 31, 2024.

There are fears the earthquakes could lead to another massive explosion reminiscent of the 1980s eruption.

In 2025, the number of earthquakes recorded per week reached a peak of 38 events per week, mostly happening around 4.6 miles below the crater floor.

Specialized equipment has detected that magma has been flowing through chambers deep underground, causing the volcano to recharge. A surge in quakes was also recorded in 2023.

'Short-term increases in earthquake rates are common at Mount St Helens and are considered part of background seismicity,' experts at the Cascades Volcano Observatory said in a statement.

'The last two periods of elevated seismicity (in 2023 and 2024) represent the largest short-term increase in earthquake rates since the last eruption ended in 2008.'

However, similar sequences involving even more quakes broke out in 1988 to 1992, 1995 to 1996, and 1997 to 1999. None of these directly triggered an eruption.

The quakes were thought to be caused by pressurization of the magma transport system, which in turn was triggered by the arrival of additional magma, a process called recharge.

Magma gradually bubbles through the lower crust and builds up in a reservoir around 2.5 to six miles below sea level. 'Recharge' events break out when magma enters this reservoir, causing quakes.

'There have been no significant changes in other monitoring parameters (ground deformation, volcanic gas or thermal emissions) and no change in hazards at Mount St. Helens as a result of this activity,' the Observatory concluded.

However, in 1980, small earthquakes were recorded at the site just before the deadly eruption.

The volcano exploded sideways and sent an enormous landslide of a super-heated mix of ash, rock fragments and gas flowing downslope. 

The ash and gas then rose, blocking the sun, turning the sky completely dark.

Destructive mudflows, also known as lahars, swept up homes and trucks as officials closed bridges and stalled railroad track operations.

Most of the debris from the seismic event turned westward, down the North Fork Toutle River and formed a mound of deposit.

The total avalanche volume equaled a measurement of one million Olympic-sized swimming pools.

Trees were also blown to the ground or scorched by the brutally hot lava, leaving the once-dense forest virtually empty.

The volcanic ash fell like snow throughout Washington, Idaho and western Montana. Officials had to close highways for weeks and airlines canceled more than 1,000 flights.

In the days following the devastation, an estimated 540 million tons of ash drifted up from the structure and settled over a total of seven states.