Geologic Publications for Mount Rainier
Surficial velocities of the Nisqually Glacier, Mount Rainier National Park, 2011 and 2012
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Laura C. Walkup
, Paul M. Kennard
, Justin G. Ohlschlager
, Scott R. Beason
Geology Program, Mount Rainier National Park
Mount Rainier, Washington is the tallest of multiple glacier-clad volcanic peaks within the Cascade Range and it contains the most glacial ice. Glaciers are the headwaters for numerous rivers emanating from Mount Rainier, many of which flow into the Puget Sound approximately 60 km (37 mi) away. Glaciers on Mount Rainier have unleashed damaging outburst floods (jökulhlaups) in the past, often without warning. Previous observations indicate an empiric link between changing glacial velocities and glacial outburst flood hazards.
This study explores whether the surficial velocity field of the Nisqually glacier is changing and whether ice velocity fluctuations indicate a change in glacial outburst flood potential. Numerous sites on the lower Nisqually glacier were surveyed weekly during late summer/early fall of 2011 and 2012. The surficial velocity field of the lower 1 km2
) of the glacier was calculated from repeated measurements. Between 2011 and 2012, observed velocities in the upper portions of the study area increased while the lower portions of the glacier slowed or remained the same. Shortly after the on-glacier study concluded, a small glacial outburst flood was released from the glacier during a minor rain event.
Our work contributes to the understanding of glacial outburst floods and provides evidence that changing ice velocities precede outburst floods. Further study of glacial velocity fields could provide a predictive methodology for glacial outburst floods in similar terrain. These results are critical for employee, visitor, and infrastructure protection in dynamic environments such as that at Mount Rainier.
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In Text Citation:
Walkup and others (2019) or (Walkup et al., 2019)
Walkup, L.C., P.M. Kennard, J.G. Ohlschlager, and S.R. Beason, 2019, Surficial velocities of the Nisqually Glacier, Mount Rainier National Park, 2011 and 2012: Unpublished Report, Geology Program, Mount Rainier National Park, 30 p..