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Lahars 24 November 2015. Vallance, 2000, EOV Downstream lahar transformations.

Published byBruno Norman Modified over 9 years ago

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Presentation on theme: "Lahars 24 November 2015. Vallance, 2000, EOV Downstream lahar transformations."— Presentation transcript:

1 Lahars 24 November 2015

2 Vallance, 2000, EOV Downstream lahar transformations

3 Vallance, 2000, EOV Downstream transformations of lahars

4 Vallance, 2000, EOV Water-saturated debris avalanches transforming to lahars downstream

5 Vallance, 2000, EOV

6

7 Mt. St. Helens – pumiceous pyroclastic flow from 1980

8 Lahars – effects on river systems and deposits

9 Lahars at Armero following the eruption of Nevado del Ruiz, 13 November 1985 Mountain front Total inundation Partial inundation No inundation

10 Lahars filling rivers following the 18 May 1980 eruption of Mount St. Helens

11 Lahar-inundated communities following the 15 June 1991 eruption of Mt. Pinatubo, Philippines

12 Breaching of levees by lahars filling river drainages after the Pinatubo eruption

13 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 hyperconc. flow

14 Rapid erosion of lahar deposits following the 18 May 1980 Mt. St. Helens eruption

15 Comparison of air photos taken in June 1978 and June 1980 of the North Fork of the Toutle River near Mt. St. Helens

16 Maximum inundation levels by lahars following the 18 May 1980 eruption of Mt. St. Helens

17 Lahar inundations and mud-coated debris after the Mt. St. Helens eruption

18 Normally graded Osceola Mudflow lahar deposit, Mt. Rainier (Vallance and Scott 1997)

19 Hummocky Osceola Mudflow deposit, Mt. Rainier (Vallance and Scott 1997)

20 Mobility of debris avalanches vs. debris flows (from Vallance and Scott 1997)

21 Cotopaxi

22 Chillos Valley lahar, Cotopaxi, Ecuador (Mothes et al 1998) ~4.5 ka, ~3.8 km 3 Note the matrix-supported and ungraded lahar deposit

23

24 Debris avalanche and lahar dispersal north of Cotopaxi

25 Comparison of lahar travel distances: Cotopaxi, Mt. St. Helens, Nevado del Ruiz south north

26 Grain size parameters as a function of distance from the source Chillos Valley lahar Osceola Mudflow

27 Grain sizes, Chillos Valley lahar

28

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