Volcanic Hazards OverviewVolcanic Hazards OverviewLecture Objectives Main types of hazards (presented here: lahars, plumes, and pyroclastic flows)lahars, plumes, and pyroclastic flows) Eruption processes General monitoring strategies !!!" # $$%& '( '''$') ''% *$*$+( *'*$&,#' # ''$%'+ '-+'**'*$'' '(-%'-$('*'##' &.' %'/0'*'('**'#''''#(% ''-%+ -(#'$'"$(12'2'$(%+ '$' 3 $'3 $'4%* "'(-'$ + )4&%- 2')+++ ' *$' *' 4'$+'-'+2 . '' &-56"&3 ' '- '-$7'(('('"* *$# +' '#' *'* &8'%'** *$ (* #' '2( $'' ( "*$$%%*# $(-*$' '-$'' (-# +'#'&.'' -$''+''%'%'*% ''''*('$%''-' %$%#''(** %'&99(from Vallance, 2000, Encyclopedia of Volcanoes) Definition: water-saturated sediment flow that moves downslope under the influence of gravity, with forces driving both solid and fluid phase flow. Lahars include debris flow (50-60% sediments by volume) and hyperconcentrated flow(water > solids), which have and hyperconcentrated flow(water > solids), which have fluvial characteristics but carry lots of sediment. Floods and muddy streamflows carry abundant sediment but are differentiated by the main fluvial processes and depositional characteristics (e.g., sorting, cross-bedding)999999Pyroclastic FlowsPyroclastic Flows3 * ' ('$7'*-2*($'(' $#'*$'#''%''$(%''&''4'$''4'$ 7% #''%*$ ' 2*($'-+& '7% #''%* #'%*$'2 #* %'4% * * %+ * *'*($'$#' ('(-+ ' *'+#''+ * &$* *$ #'''*$'% * &Effects of pyroclastic flowsA pyroclastic flow will destroy nearly everything in its path. With rock fragments ranging in size from ash to boulders traveling across the ground at speeds typically greater than 80 km per hour, pyroclastic flows knock down, shatter, bury or carry away nearly all objects and structures in their way. The extreme temperatures of rocks and gas inside pyroclastic flows, generally between 200°C and 700°C, can cause combustible material to burn, especially petroleum products, wood, vegetation, and houses.
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