Sand Mountain Field

Geography & Climate

Sand Mountain Field is located in United States, within the High Cascades Volcanic Arc of the broader North America Volcanic Regions. Situated at 44.38° N, 121.93° W in the Northern Hemisphere, the volcano lies within a temperate climate zone. With a summit elevation of 1,664 meters above sea level, Sand Mountain Field is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a cluster, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Sand Mountain Field sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in United States near Sand Mountain Field, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is basalt / picro-basalt, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

Eruption History Summary

Sand Mountain Field has 2 recorded eruptions in the geological database, spanning from 5050 BCE to 950 BCE. The most powerful recorded event was a cataclysmic eruption with ash columns reaching the stratosphere in 950 BCE, reaching VEI 4 on the Volcanic Explosivity Index. These eruptions span roughly 4,100 years of volcanic history.

Significance

With a maximum recorded VEI of 4, Sand Mountain Field has demonstrated the capacity for significant explosive eruptions that can impact regional aviation, agriculture, and communities tens of kilometers from the summit. VEI 4 eruptions produce ash columns reaching 15-25 kilometers into the atmosphere.

GVP Reference Summary

The Sand Mountain volcanic field consists of 23 basaltic and basaltic andesite cinder cones along a N-S line immediately west of the Cascade crest NW of Mount Washington. Two cone alignments trending NNW and NNE intersect near the largest cinder cone, Sand Mountain. Although previous radiometric dates spanned a range of more than a thousand years, tightly constrained paleomagnetic ages imply that at least 13 eruptive units were emplaced in a relatively short period of time about 2,950 years ago lasting at most a few decades. The Jack Pine vent at the northern end of the field is compositionally distinct from the rest of the volcanic field and is considered to have been erupted about 4,000 years earlier. Lava flows traveled predominately to the west, blocking local drainages and forming several small lakes.

— Smithsonian Institution, Global Volcanism Program