Widely recognized as Portland’s signature peak, Mt. Hood, Oregon, is categorized by the US Geological Survey as a “very high threat" volcano. Mt. Hood poses numerous risks to major population centers, from pyroclastic flows to lahars that have crossed the Columbia River. And while eruptions present immediate challenges, volcanic sediments may impact downstream communities years later. The 2026 SZ4D Mt Hood Pilot Project sought to understand how post-eruptive sedimentary processes contribute to Mt. Hood’s threat potential.

The Pilot Project was designed as an “incubator,” a space to inspire new ideas and provide a multidisciplinary group of scientists the agency to start their own research. According to Madison Myers, a key organizer of the SZ4D GeoArray team, “...the field trips were based on trying to bring people from… different disciplines to try to research a common feature. Further, we wanted to develop strategies to foster and support multidisciplinary projects rather than based in subdisciplines.” An international team of 27 geoscientists spanning career stages collaborated with SZ4D for a ten day field excursion to Mt. Hood. Through a series of interdisciplinary field investigations, the team collected new data, and developed a holistic understanding of the volcano’s current and future geohazards.

Nearby, Mt. St Helens is famous for its large-volume explosive eruption in 1980. Mt. Hood’s own geologic history, in contrast, Mt. Hood lacks evidence for similar large-volume events. Its 1781 eruption, known as the “Old Maid” period, is notable for the collapse of a lava dome that generated pyroclastic density currents. A section of the flow detached to form a diluted surge, which traveled southward down the volcano’s flanks. During the field trip, the participants mapped the extent of the surge (figure 1), locating deposits that border the popular Timberline Lodge ski resort. Initial field observations suggest that these deposits have a more silica-rich composition than the previous Timberline flow. 

Volcanic debris supplies sediment to the nearby White River, where remobilization triggers cascading hazards such as lahars and debris flows. In collaboration with the Oregon Department of Transportation (ODOT), the SZ4D team investigated sediment transport along the White River. Whereas lahars remain uncommon, long-term bridge inundation presents logistical challenges to ODOT. Participants studied 24 riverbed transects spaced 200 meters apart, combining grain-size measurements (figure 2) with new drone surveys and existing LiDAR maps. While solutions remain a work in progress, understanding these dynamics will help identify strategies to reduce impacts on critical infrastructure.

In addition to recent volcanism, the Mt. Hood region is cut by numerous Quaternary faults. During transect work, a group of participants studied a NNE-trending fault system on the eastern side of the White River. They measured fault orientations and photographed the outcrop to produce a 3D model of the White River watershed (figure 3). This data will be used to evaluate the fault system as a potential continuation of the larger NNE striking Twin Lakes Fault. Participants also visited the nearby Tilly Jane Fault to further assess seismic risk. They drilled five boreholes on both sides of the fault, then analyzed differences in the characteristics of the ash within the cores. 

Although sediment transport was the primary focus of the Pilot Project, the fieldwork also opened opportunities to investigate older eruptions at Mt Hood. Participants collected samples for detrital zircon geochronological work, which aims to provide new age constraints on the volcanic deposits. The Old Maid deposits overlie 120,000 year old andesite flows, where participants noticed unusual horizontal jointing described as “platy”. The team measured fracture orientations and concentrations to determine the direction of stress on the lava. These data will help assess how topography affects the rheology of lava flows.

The work initiated during the field trip continued beyond the field site. Several participants have submitted abstracts to conferences such as the American Geophysical Union, the Geological Society of America, and the VIII Colloquium on Geophysical Signatures or Earthquakes, Volcanoes and Landslides. Future Pilot Projects will build on this approach, re-evaluate past work at Mt. Hood while promoting interdisciplinary collaboration. By fostering collaboration across traditional discipline boundaries, this continued research empowers communities to make informed decisions that prioritize safety and responsible development. 

Learn more | Read the postcards from the field from field participants