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