What Makes Mount Rainier the Most Dangerous Volcano in the U.S.?

Image Credit: Phys.org

Mount Rainier, a magnificent peak in Washington state that stands 4.3 kilometers (2.7 miles) above sea level, has not erupted appreciably in the last millennium. Despite its extended dormancy, the volcano remains a significant threat, which has many US volcanologists on alert. Unlike Hawaii’s ongoing lava flows and Yellowstone’s supervolcano, Mount Rainier keeps scientists awake at night, fearful of its potential for cataclysmic destruction.

Lahars—fast-moving rivers of water and volcanic debris—are Mount Rainier’s major threat, rather than flaming lava flows. These dangerous mudflows occur when an eruption swiftly melts the mountain’s considerable ice and snow, mixing it with volcanic rock and other debris. The ensuing slurry can flow down slopes and drainage canals, killing everything in its path.

Seth Moran, a research seismologist at the US Geological Survey’s Cascades Volcano Observatory in Vancouver, Washington, highlights the unique danger of Mount Rainier. “The thing that makes Mount Rainier tough is that it is so tall, and it’s covered with ice and snow. If there is any kind of eruptive activity, hot stuff will melt the cold stuff, and a lot of water will start coming down,” he explains. This poses a significant risk to the tens of thousands of people living in the potential path of a large lahar.

Lahars have proven deadly in the past. In November 1985, Colombia’s Nevado del Ruiz volcano erupted, triggering a lahar that obliterated the town of Armero, killing over 23,000 people within minutes. Mount Rainier has about eight times the amount of ice and snow as Nevado del Ruiz did, suggesting a potential for even more catastrophic mudflows.

Bradley Pitcher, a volcanologist at Columbia University, shares these concerns. He observes that prior lahars from Mount Rainier have extended deep into the Puget Lowlands, damaging Tacoma and South Seattle, which are built on old mudflows from previous eruptions.

Given this concern, the United States Geological Survey (USGS) has installed a thorough lahar detection system on Mount Rainier. Since its beginning in 1998, the system has been continually improved, with approximately 20 monitoring locations currently equipped with broadband seismometers, trip wires, infrasound sensors, web cameras, and GPS receivers. This system is intended to detect volcanic eruptions and landslide-induced lahars in real-time.

In addition to technological monitoring, community preparedness is crucial. Around 45,000 students from various Washington school districts participated in the world’s largest lahar evacuation drill in March. This exercise saw 13,000 students walking up to 3.2 kilometers (2 miles) to designated safe zones, while others practiced sheltering in place. These drills underscore the importance of readiness in the face of potential natural disasters.

While Mount Rainier has been quiet for centuries, geologists warn that it is still capable of sudden, catastrophic events. The last significant lahar occurred around 500 years ago, likely triggered by a massive landslide rather than volcanic activity. The presence of loose, unstable rock on the mountain’s slopes remains a constant threat, capable of causing spontaneous lahars.

A 2022 study modeled potential worst-case scenarios, demonstrating how a lahar originating on Mount Rainier’s west side could travel swiftly to populated areas like Orting, Washington, within an hour. These simulations show lahars moving at speeds of 4 meters (13 feet) per second, carrying volumes equivalent to 104,000 Olympic-sized swimming pools.

Given the short warning periods for lahars, community planning and timely action are critical. The USGS has strategically placed fail-safe components of the lahar detection system to enhance evacuation time. These precautions are critical for the safety of persons living in high-risk areas. Venus Dergan, one of the few survivors of a lahar caused by Mount St. Helens’ eruption in 1980, emphasizes the unpredictability and danger of these catastrophes. Her terrifying experience of being swept away and almost buried by mud and debris serves as a sharp warning of the possible risks.

Mount Rainier, despite its serene aspect, represents a severe hazard due to its propensity to cause destructive lahars. Continuous monitoring, technology developments, and community readiness are critical to reducing the threats connected with this sleeping behemoth. As scientists continue to research and prepare for future eruptions, the significance of awareness and readiness cannot be emphasized. In the area of global conflicts, natural disasters such as Mount Rainier remind us of the constant necessity for awareness and preparedness in protecting our communities.

As reported by the CNN in their recent article