Volcano fact sheet; glacier-generated debris flows at Mount Rainier

AbstractDestructive debris flows occur frequently at glacierized Mount Rainier volcano, Washington, U.S.A. Twenty-three such flows have occurred in the Tahoma Creek valley since 1967. Hydrologic and geomorphic evidence indicate that all or nearly all of these flows began as outburst floods from South Tahoma Glacier. Flood waters are stored subglacially. The volume of stored water discharged during a typical outburst flood would form a layer several centimeters thick over the bed of the entire glacier, although it is more likely that large linked cavities account for most of the storage. Statistical analysis shows that outburst floods usually occur during periods of atypically hot or rainy weather in summer or early autumn, and that the probability of an outburst increases with temperature (a proxy measure of ablation rate) or rainfall rate. We suggest than outburst floods are triggered by rapid water input to the glacier bed. causing water-pressure transients that destabilize the linked-cavity) system, The correlation between outburst Hoods and meteorological factors casts doubt on an earlier hypothesis that melting around geothermal vents triggers outburst floods from South Tahoma Glacier.

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Glacier Outburst Floods at Mount Rainier, Washington State, U.S.A.

Annals of Glaciology ◽

10.1017/s0260305500007631 ◽

1989 ◽

Vol 13 ◽

pp. 51-55 ◽

Cited By ~ 13

Author(s):

Carolyn L. Driedger ◽

Andrew G. Fountain

Keyword(s):

Debris Flows ◽

Monitoring Program ◽

Washington State ◽

Cascade Range ◽

Hydraulic Pressure ◽

Flood Water ◽

Outburst Floods ◽

Mount Rainier ◽

Volcanic Debris ◽

Southern Flank

During the twentieth century, glacial outburst floods have been the most destructive natural events on Mount Rainier, a stratovolcano in the Cascade Range in Washington State, U.S.A. In the period between 1930 and 1980 numerous floods were reported from five glaciers on the mountain, most of which flowed from Nisqually, Kautz, or South Tahoma Glaciers on its southern flank. Such floods threaten lives and property because they occur without warning and quickly mobilize the loose volcanic debris into debris flows. A monitoring program was begun in 1987 which was designed to measure the dimensions and timing of outburst floods, but this has been unsuccessful because no floods have yet occurred on the monitored streams. Four floods did burst from South Tahoma Glacier that was unmonitored, but in spite of this they have been useful in providing evidence of flood storage and release mechanisms. All flood volumes were found to be of approximately similar orders of magnitude, of 1 × 105 m3 of water, indicating that all floods probably had similar mechanisms for storage and release of water. Hydraulic pressure considerations indicate that such a large volume of flood water would be stored at the bed of the glacier rather than in isolated englacial cavities. The stepped bedrock terrain provides an ideal setting for the formation of subglacial cavities capable of storing the volumes of flood water noted.

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Sedimentology, Behavior, and Hazards of Debris Flows at Mount Rainier, Washington

Professional Paper ◽

10.3133/pp1547 ◽

1995 ◽

Cited By ~ 52

Author(s):

K.M. Scott ◽

J.W. Vallance ◽

P.T. Pringle

Keyword(s):

Debris Flows ◽

Mount Rainier

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Glacier Outburst Floods at Mount Rainier, Washington State, U.S.A.

Annals of Glaciology ◽

10.3189/s0260305500007631 ◽

1989 ◽

Vol 13 ◽

pp. 51-55 ◽

Cited By ~ 10

Author(s):

Carolyn L. Driedger ◽

Andrew G. Fountain

Keyword(s):

Debris Flows ◽

Monitoring Program ◽

Washington State ◽

Cascade Range ◽

Hydraulic Pressure ◽

Flood Water ◽

Outburst Floods ◽

Mount Rainier ◽

Volcanic Debris ◽

Southern Flank

During the twentieth century, glacial outburst floods have been the most destructive natural events on Mount Rainier, a stratovolcano in the Cascade Range in Washington State, U.S.A. In the period between 1930 and 1980 numerous floods were reported from five glaciers on the mountain, most of which flowed from Nisqually, Kautz, or South Tahoma Glaciers on its southern flank. Such floods threaten lives and property because they occur without warning and quickly mobilize the loose volcanic debris into debris flows.A monitoring program was begun in 1987 which was designed to measure the dimensions and timing of outburst floods, but this has been unsuccessful because no floods have yet occurred on the monitored streams. Four floods did burst from South Tahoma Glacier that was unmonitored, but in spite of this they have been useful in providing evidence of flood storage and release mechanisms. All flood volumes were found to be of approximately similar orders of magnitude, of 1 × 105 m3 of water, indicating that all floods probably had similar mechanisms for storage and release of water. Hydraulic pressure considerations indicate that such a large volume of flood water would be stored at the bed of the glacier rather than in isolated englacial cavities. The stepped bedrock terrain provides an ideal setting for the formation of subglacial cavities capable of storing the volumes of flood water noted.

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