Mount Baker is rated a very high threat volcano, yet much of its monitoring was dismantled

Mount Baker carries the same Very High Threat label the USGS assigns to only 18 volcanoes nationwide, yet the agency’s own profile of the mountain says much of its monitoring equipment has been dismantled and that current coverage is now insufficient for the danger renewed activity would pose. The 3,286-meter volcano, the tallest peak in Washington’s North Cascades, last erupted about 6,700 years ago, but its Sherman Crater has vented steam continuously since 1975, a reminder that a long quiet stretch is not the same thing as an inactive volcano.

That gap between a top-tier hazard rating and a thinned-out sensor network is now the subject of active USGS work rather than a settled problem, with new modeling due for review in the next year.

Steam that never really stopped

Sherman Crater’s plume dates to 1975 and 1976, when the USGS’s Mount Baker profile says the volcano showed “signs of renewed volcanic activity as a result of magma intruding into the volcano but not erupting.” Steam emissions rose sharply that year and never fully returned to their earlier, quieter baseline, which is why the agency still describes the crater as a site of increased steam emission five decades later. Mount Baker’s last major eruption predates any of that by thousands of years, sending lahars down the Middle Fork and Nooksack Rivers and across its east flank roughly 6,700 years ago.

Nate Stevens, a staff seismologist with the Pacific Northwest Seismic Network, has said that Mount Baker produces more low-frequency earthquakes than any other Cascade volcano, most of them tied to glacial movement rather than rising magma. Distinguishing the two signal types, he said of one recent swarm, led researchers to conclude “it’s not magma rising, it’s hot water inside the earth” moving through the mountain’s plumbing, a distinction that takes careful analysis because the two sources of shaking can look nearly identical on a seismometer readout.

USGS on the dismantled monitoring network

The USGS profile does not soften the finding: “much of it has been dismantled and monitoring at Mount Baker is now insufficient due to the threat that renewed activity would pose to nearby communities and regional infrastructure.” The agency names Mount Baker as one of several Cascade volcanoes it considers a high priority for restored and expanded monitoring, a category that competes for limited federal funding against dozens of other very-high and high-threat volcanoes across five states.

Current instrumentation still exists. The Cascades Volcano Observatory and the Pacific Northwest Seismic Network jointly operate two seismic stations within 20 kilometers of the summit, supplemented by periodic measurements of water chemistry, temperature, and ground deformation. That is a fraction of the sensor density the USGS maintains at Mount St. Helens, where decades of eruptive activity justified building out what the agency calls the best-monitored volcano in the entire Cascade Range. The observatory’s stated mission is to help people “live knowledgeably and safely with volcanoes in Washington, Oregon, and Idaho,” a goal that depends on having enough instruments in the ground to notice trouble early rather than after the fact.

New modeling, old lahar paths

Mary Benage, a research geophysicist with the Cascades Volcano Observatory, is part of a team updating numerical models of how a future Mount Baker lahar would move, work a regional report said is expected to reach USGS review in early-to-mid 2026. The largest known lahar on record traveled roughly 7.5 miles down the Nooksack River drainage with depths exceeding 325 feet, burying a valley now home to farms, roads, and small communities that did not exist when the flow occurred.

Matt Klein, deputy director of Whatcom County’s Division of Emergency Management, has been coordinating with USGS scientists on what better monitoring and updated hazard maps would mean for evacuation planning along that same river corridor, where warning time currently depends on instruments the agency itself says are stretched thin. Whatcom County’s own hazard planning already assumes a lahar could reach populated stretches of the valley faster than residents could be individually notified door to door, which is why updated modeling matters as much for siren placement as for pure science.

A ranking meant to direct scarce resources

Mount Baker’s Very High designation comes from the National Volcano Early Warning System, the same federal framework that ranks 18 U.S. volcanoes at that top tier, 11 of them in Washington, Oregon, or California, according to the USGS’s 2018 update to its national threat assessment. John Ewert, the geologist who led that update, has said the ranking exists to focus monitoring dollars where they matter most rather than to predict which volcano erupts next, a distinction that matters for a mountain whose greatest risk may be how little of it is currently being watched.

The full threat-assessment report scores volcanoes on two dozen hazard and exposure factors, and Mount Baker’s combination of glacier-fed lahar potential and nearby population centers keeps it near the top of that list even as its instrument count lags behind less isolated peaks.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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