5 km north-south and up to 10 km east-west, with an aerial extent

of approximately 160 km2. There is no indication of temporal overlap in the activity of the three major volcanic complexes on Montserrat (Cassidy et al., 2012). Consistency between the type of deposits present across the island suggests that the andesitic dome forming style of eruption is common to SH, CH and SHV. The only exception is SSH which possesses basaltic and basaltic–andesite lava flows (Zellmer et al., 2003) and is likely to have some temporal overlap with the early activity of SHV. The apparent consistency in eruptive style means that the island’s volcanic centres provide a unique insight into the temporal evolution of a system, from the building of a complex volcanic edifice (SHV) to the eventual TSA HDAC ic50 erosion back to the central core and most proximal deposits of an extinct volcano (SH). The last 15 years of eruption at SHV have been characterised by periods of dome growth and subsequent collapse. The domes selleck grow by extrusion of highly viscous andesitic spines that break off to form blocky, often unstable, talus slopes. Between 1995 and 2009 SHV erupted an estimated 1 km3 dense rock equivalent (DRE) of andesite magma (Wadge

et al., 2010). As the domes grow they can become gravitationally unstable or undermined by slope weakening associated with hydrothermal activity (Sparks et al., 2002). Dome collapses generate volcaniclastic deposits, including clay-rich debris avalanches, pyroclastic flows, surges and lahars (Cole et al., 1998). Collapses have also been triggered by violent vulcanian explosions that produce pumice-rich

flows, surges and lahars, as well as significant volumes of ash (Druitt et al., 2002). The resultant geology is characterised by variably fractured, though relatively competent, cores of andesitic dome rock and talus breccia, surrounded by volcaniclastic aprons. These flanking deposits are often referred to as andesite tuffs (Rea, 1974), though they vary in the proportions of andesite lava blocks, pumice and ash. Such geological framework is not uncommon at dome building composite volcanoes (Fisher et al., 2006) and is observed throughout the Lesser Antilles, for example, Guadeloupe, Martinique, Dominica and St Lucia (Sigurdsson et al., 1980). During periods of repose, erosional forces Methane monooxygenase dominate, expedited by high rainfall, tropical storms and the humid climate (see Section 3). Frequent heavy rain cuts deeply incised radial valleys (locally termed ghauts) and reworks channel fill deposits. Periods of low or no volcanic activity also allow the development of weathered surfaces and soils. Rad et al. (2007) described conglomerate and sand pyroclastic soils, with thicknesses up to 70 m, on the Lesser Antilles islands of Guadeloupe and Martinique. Their study suggests subsurface weathering is considerable, owing to the high permeability and porosity of young pyroclastic deposits.