lahars 24 november 2015. vallance, 2000, eov downstream lahar transformations
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Lahars
24 November 2015
Vallance, 2000, EOV
Downstream lahar transformations
Vallance, 2000, EOV
Downstream transformations of lahars
Vallance, 2000, EOV
Water-saturated debris avalanches transforming to lahars downstream
Vallance, 2000, EOV
Vallance, 2000, EOV
Mt. St. Helens – pumiceous pyroclastic flow from 1980
Lahars – effects on river systems and deposits
Lahars at Armero following the eruption of Nevado del Ruiz, 13 November 1985
Mountain front
Total inundation
Partialinundation
No inundation
Lahars filling rivers following the 18 May 1980
eruption of Mount St. Helens
Lahar-inundated communities following the 15 June 1991 eruption of Mt. Pinatubo, Philippines
Breaching of levees by lahars filling river drainages after the Pinatubo eruption
Pumice-rich debris flow deposit, east side Mt. Pinatubo, 20-21 Aug 1991
Above - Debris flow (unstratified) and hyperconcentrated flow (stratified) deposits, east side Mt. Pinatubo
Lake breakout deposits, east side Mt. Pinatubo
debris flow
debris flow
hyperconc. flow
Rapid erosion of lahar deposits following the 18 May 1980 Mt. St. Helens eruption
Comparison of air photos taken in June 1978 and June 1980 of the North Fork of the Toutle River near Mt. St. Helens
Maximum inundation levels by lahars following the 18 May
1980 eruption of Mt. St. Helens
Lahar inundations and mud-coated debris after the Mt. St. Helens eruption
Normally graded Osceola Mudflow lahar deposit, Mt. Rainier(Vallance and Scott 1997)
Hummocky Osceola Mudflow deposit, Mt. Rainier(Vallance and Scott 1997)
Mobility of debris avalanches vs. debris flows (from Vallance and Scott 1997)
Cotopaxi
Chillos Valley lahar, Cotopaxi, Ecuador(Mothes et al 1998)
~4.5 ka, ~3.8 km3
Note the matrix-supported and ungraded lahar deposit
Debris avalanche and lahar dispersal north of Cotopaxi
Comparison of lahar travel distances:
Cotopaxi, Mt. St. Helens, Nevado del Ruiz
south
north
Grain size parameters as a function of distance from the source
Chillos Valley lahar
Osceola Mudflow
Grain sizes, Chillos Valley lahar
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