avalanches

avalanches - Avalanches Avalanches Avalanches were first...

Info iconThis preview shows pages 1–15. Sign up to view the full content.

View Full Document Right Arrow Icon
Avalanches Avalanches
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Avalanches were first imagined as giant snowballs which increased in size from accretion of underlying snow
Background image of page 2
What are avalanches? They are  flows  which move under the  influence of  gravity They can be  channelized or unconfined In this sense, they are similar to pyroclastic  flows, debris flows, etc.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Avalanches have severe consequences Direct effects: impact burial Indirect effects: tsunamis generated if an avalanche enters a  lake
Background image of page 4
Avalanche zones a)  Starting zone:  where an avalanche is  initiated b)  Avalanche track:  where it goes c)  Runout area:  where it dissipates
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
a) Starting zones of avalanches F s  = Safety Factor F s  = (shear strength)/(shear stress) shear strength:  internal resistance to movement shear stress:  force causing movement parallel to  slope; increases with slope angle If F s  is less than 1, then the slope is unstable and 
Background image of page 6
Shear stress On a slope, gravity has two components, one at right angles to the slope (g p ), and the other parallel to the slope (g s ) As the slope angle increases, g p decreases while g s  increases At a certain point, g s  exceeds the shear strength, and failure of the mass occurs
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Layering of snow
Background image of page 8
Two weak layers within a slab
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Initial failure - two types Surface or near-surface Failure at depth More dangerous
Background image of page 10
Loose snow failure
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Slab  failure
Background image of page 12
b) Internal structure of the flow 2 types of snow avalanche (a spectrum exists): flow avalanches airborne powder snow avalanches Density and solids concentration gradient
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Avalanche flow structure Note the head, body, and tail of the flow Vertical and lateral  gradients  in solids  (i.e., snow)  concentration and in density: a lower dense portion which is highly hazardous 
Background image of page 14
Image of page 15
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 55

avalanches - Avalanches Avalanches Avalanches were first...

This preview shows document pages 1 - 15. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online