ABSTRACT
In Central America, as in other regions on Earth, highly explosive, plinian volcanic eruptions generate buoyant eruption columns capable of penetrating up to 40 km high into the stratosphere, until they reach the level of neutral buoyancy and spread laterally. Such eruption clouds drift with the prevailing wind and gradually drop their ash load over areas sometimes larger than 105 km2. The resulting ash layers are best preserved in non-erosive marine or lacustrine environments which thus provide the most complete record of volcanic activity. Wide aerial distribution across sedimentary facies boundaries, near-instantaneous emplacement, chemical signatures facilitating stratigraphic correlations, and the presence of minerals suitable for radiometric dating make these ash layers excellent stratigraphic marker beds. Marine tephrostratigraphy provides constraints on the temporal evolution of both the volcanic source region and the ash-containing sediment facies. The presence of chemically reactive volcanic glass particles also affects the diagenetic evolution of the sediments.
