02535nas a2200289   4500000000100000008004100001653001400042653001500056653001700071653001400088653002800102100002200130700001800152700001500170700001900185700001900204700001300223700001200236700001600248700002000264700001900284700001700303245020000320300002200520490000700542520169600549       2013                            d10amass flow10aMontserrat10astratigraphy10asubmarine10avolcanoclastic deposits1 aJessica Trofimovs1 aPeter Talling1 aJ.K Fisher1 aStephen Sparks1 aSebastian Watt1 aM.B Hart1 aC Smart1 aA Le Friant1 aMichael Cassidy1 aSteven Moreton1 aMelanie Leng00aTiming, origin and emplacement dynamics of mass flows offshore of SE Montserrat in the last 110 ka: Implications for landslide and tsunami hazards, eruption history, and volcanic island evolution  a385\textendash4060 v143 a<p>Mass flows on volcanic islands generated by volcanic lava dome collapse and by larger-volume flank collapse can be highly dangerous locally and may generate tsunamis that threaten a wider area. It is therefore important to understand their frequency, emplacement dynamics, and relationship to volcanic eruption cycles. The best record of mass flow on volcanic islands may be found offshore, where most material is deposited and where intervening hemipelagic sediment aids dating. Here we analyze what is arguably the most comprehensive sediment core data set collected offshore from a volcanic island. The cores are located southeast of Montserrat, on which the Soufriere Hills volcano has been erupting since 1995. The cores provide a record of mass flow events during the last 110 thousand years. Older mass flow deposits differ significantly from those generated by the repeated lava dome collapses observed since 1995. The oldest mass flow deposit originated through collapse of the basaltic South Soufriere Hills at 103\textendash110 ka, some 20\textendash30 ka after eruptions formed this volcanic center. A \~1.8 km3 blocky debris avalanche deposit that extends from a chute in the island shelf records a particularly deep-seated failure. It likely formed from a collapse of almost equal amounts of volcanic edifice and coeval carbonate shelf, emplacing a mixed bioclastic-andesitic turbidite in a complex series of stages. This study illustrates how volcanic island growth and collapse involved extensive, large-volume submarine mass flows with highly variable composition. Runout turbidites indicate that mass flows are emplaced either in multiple stages or as single events.</p>