mudslides around mt. rainier

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Mud / Waterflows around Mount Rainier

Major Mudflows*
Flow	Age (years)	Volume (km³)	River Valley	Area Reached
Tahoma Lahar	<500	<0.15	Tahoma Creek Nisqually River	Probably to Elbe
Electron Mudflow	530-550	0.26	Puyallup River	Puget Sound Lowland
Unnamed Mudflow	1050-1000	>0.30	Puyallup River	At least to Mowich River; possibly Puget Sound
Round Pass Mudflow	2170-2710	?	Puyallup River	Puget Sound Lowland
Osceola Mudflow	4500-5000	3	White River and West Fork	Puget Sound

Smaller Mudflows
Flow	Age or Date	Volume (km³)	River Valley	Area Reached
Little Tahoma Peak Lahar/Avalanche	1963	0.01	White River	White River Campground
Tahoma Glacier Avalanche	1910-1930	0.01	Puyallup River	Below end of glacier
Round Pass Mudflow	2610-2790	<0.01	Tahoma Creek; Nisqually River	End of Tahoma Creek
Pre-Y level Lahar	>3400	?	Puyallup River; Tahoma Creek	Unknown
Paradise Lahar	4500-5000	0.1	Paradise River; Nisqually River	At least to National

Large Muddy Outburst Floods*
River Valley and Flow	Age or Date	Area Reached
White River (including West Fork):
Gravel-rich flow	~1550 AD	At least to Mud Mountain Reservoir
At least one lahar	>1480 AD	At least 5-10 mi outside of Park boundary
Lahar in West Fork	<2200	At least to confluence of forks
Lahar?	<2200	? possibly to Puget Sound
Many lahars	<2200	Probably to Puget Sound
At least 5 lahars	<4500	Probably to edge of Puget Sound Lowland
At least two lahars	>5000	Puget Sound Lowland
Cowlitz River:
At least two flows	post 1480 AD	At least 10 km downstream of Packwood
Lahar	<2200	Packwood
At least 3 lahars	<3400	At least to Park boundary on Muddy Fork
Nisqually River:
Outburst flow on Kautz Creek	1947 AD	Below confluence with Nisqually River
Lahar	post 1480 AD	At least to Elbe
Parts of Tahoma Lahar	post 1480 AD	At least to Elbe
Lahar runout	<2500	At least to National
Lahar runout	<2500	To Elbe
Runout from National Lahar	<2200	Puget Sound
Lahar runout	<3400	At least to Ashford
Large lahar runout	>3400	Probably to Puget Sound Lowland
Puyallup River:
Lahar runout	<3400	Puget Sound Lowland
Lahar	<3400	Puget Sound Lowland
Lahar runout	3400	Puget Sound Lowland
Carbon River:
Lahar runout	post 1480 AD	At least 5 km below end of glacier
Lahar runout	pre 1480 AD	8-10 km beyond end of glacier

*Mudflow and muddy outburst floods are descriptive terms used here in place of technical terms such as cohesive debris flows used in the original report. These data cover a range of flows consisting of differing proportions of mud and water. Mudflows are like huge rivers of mud. These flows always leave deposits of mud that later dry to rich soil. Muddy outburst floods are more like floods of muddy water. These flows may be erosive or may leave deposits. Small muddy flows and glacial outbursts of mostly water are not listed because they are difficult to detect from river deposits. Lahar refers to the whole range of muddy flows. Lahar runout refers to muddy water flowing out of a mudflow that has stopped.

Some Properties of Mud/Water Flows
	Giant Mudflows	Large Mudflows	Muddy Floods
Flow Volume	>3 km³	0.1-0.5 km3	<0.1 km3
Flow Speed at:
Volcano Base	>40 m/s	>30 m/s	10 m/s
1 km out on plain	10	8	3-4
Flow Height at:
Volcano Base	200 m	50 m	15 m
1 km out on Plain	30	10	1-3

These data are adapted from U.S. Geological Survey Open-File Report 90-385.

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