K Nemeth, C Risso, F Nullo, G Kereszturi , 2011. The role of collapsing and rafting of scoria cones on eruption style changes and final cone morphology: los morados scoria cone, Mendoza, Argentina. XXV IUGG General Assembly "Earth on the Edge: Science for a Sustainable Planet" 28 June - 7 July 2011, Melbourne Convention & Exhibition Centre, Melbourne, Australia. Abstract USB #5146

Payún Matru Volcanic Field is a young monogenetic volcanic field that hosts scoria cones of perfect to breached cone morphologies. Los Morados represents an eruption that was long lived (months to years). After the initial stage, the eruption entered to a normal Strombolian cone-building style, generating a cone over 150 metres in height on a northward dipping (~4°) surface. The cone gradually achieved gravitational instability that was facilitated even further by a lava flow outbreak in the cone's base that rafted up to 10 % of the total volume of the initial cone. A sudden sector collapse initiated a dramatic decompression in the upper conduit that triggered a singular violent Strombolian style eruption. Subsequently the eruption became more stable, and transformed to a typical Strombolian style eruption that partially rebuilt the cone. Due to a likely increase of magma flux, and the gradual growth of the cone, a renewed lava flow outbreak in the structurally weakened earlier breach site removed, for the second time, the unstable flank of the cone, triggering a second violent Strombolian eruption that was followed by a Hawaiian style lava fountaining. The lava fountaining was accompanied by steady voluminous lava flow emissions, which were counteracted by the constant rafting of the cone flank, preventing the healing of the cone. Our evidence shows that scoria cone growth is a complex process, and it is in a constant balance between the magma internal parameters (volatile content, magma flux, recharge, output volume) and external eruptive environmental conditions (gravitational instability).

1. IAVCEI Commission on Monogenetic Volcanism