An objective method for mapping hazardous flow deposits from the stratigraphic record of stratovolcanoes: a case example from Montagne Pelee

A method is described that enables a variety of maps, which indicate the pr obabilities of deposition, to be constructed in a reproducible manner from the stratigraphic information typically available at well-studied stratovol canoes. These maps can then be used as a basis for hazard assessment. The s ampling of the deposits of previous eruptions is subject to uncertainties d ue to erosion, sectoral deposition and non-exposure. A model-based, iterati ve algorithm is used to compensate for the incomplete sampling. For each si te, the available evidence from the other sites is used to estimate the pro bability of deposition for missing deposits. A geographical information sys tem (GIS)-based method that uses Thiessen polygons to represent the presenc e or absence of deposits, together with simple cartographic rules based on depositional processes, then defines the extent of deposition. The combined operation of these two techniques is presented for Montague Pelee in Marti nique, using the amended stratigraphic record of Smith and Roobol (1990) fo r the past 6000 years. Three types of maps are created: maps for individual depositional events (the 1902 block-and-ash flow and surge deposits are us ed to verify the technique), maps for different deposit types aggregated ov er 6000 years of activity; and scenario maps which, in Montagne Pelee's cas e, recognise that during the next Peleean or Plinian eruption a variety of hazards will have to be confronted.