22 Evolution of Cordilleran-type orogenic systems (Posters)

This session seeks contributions that connect surface, crustal, and mantle processes associated with Cordilleran systems, specifically addressing geodynamics, kinematics, magmatism, uplift, erosion, basin subsidence, and sediment dispersal in ancient and modern settings.

Thursday, 23 April 2026
8:00 AM - 5:30 PM
LMH, 5th Floor Chapel

Hazardous Origins of Cascade Range Lakes

Paper number: 22-3
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The origin of lakes perched near the crest of high mountain ranges are commonly attributed to recent glacial processes, but volcanic, tectonic, and precipitation factors may also play a role. Our study of several lakes in the Cascade Range near Mount Hood involves lidar analysis, geologic mapping, paleoseismology, and geochronology. Preliminary results suggest that multiple high-elevation lakes in this region were instead formed by recent volcanism, faulting, and landsliding that blocked the upper reaches of high-elevation drainages. South of Mount Hood, Twin, Frog, Anvil, Dinger, and Clear lakes formed above the down-thrown side of active normal faults with 10’s of m of total offset. The uphill-facing nature of these fault scarps have impounded drainages near the Cascade Range drainage divide. Lidar-based geologic mapping coupled with terrestrial and lacustrine paleoseismology indicates that Holocene surface-rupturing earthquakes contributed to continued lake subsidence. Pending Ar/Ar ages from Cascade arc volcanic rocks will provide a maximum age of fault activity and lake formation. North of Mount Hood, a new Ar/Ar age (134.2 ± 2.2 ka) from the Lost Lake volcano indicates that the adjacent Lost Lake formed in late Pleistocene time after the volcano blocked the upper reach of Laurel Creek, possibly enhanced by subsequent glaciation. Northwest of Mount Hood, Bull Run Lake was formed after landsliding blocked the uppermost reach of the Bull Run River. The landslide was sourced from undated lavas exposed at cliffs at Preacher Peak at the crest of the Cascade Range. The undisturbed nature of the landslide deposit perched near the uppermost, glaciated reach of the valley suggests it failed after the Last Glacial Maximum. Recent observations of the 7.7-ka Mazama ash in cores from the lake suggest the landslide-dammed lake formed prior to this eruption. In the Columbia River Gorge, a recent dendrochronology study indicates that the Bonneville landslide blocked the Columbia River and formed the >200 km-long Lake of the Gods in AD 1446-1447. Paleoseismology of the nearby Mount Hood fault zone documents a ~M7 surface-rupturing earthquake that occurred around this time, suggesting that strong seismic shaking may have caused landsliding and lake formation. These results highlight how hazardous volcanic, earthquake, and landslide processes play an important role in landscape evolution and recent lake formation in the Cascade Range.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3

doi: 10.1130/abs/2026CD-410871

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