Shallow dike emplacement and related hazard in central stratovolcanoes

Abstract

In the crust, the orientation of a dike is controlled by the orientation of the principal stresses, with the dike orthogonal to the least compressive stress. At shallower levels, the presence of a volcanic edifice introduces significant deviations from expected patterns. The load of the edifice focuses the stresses above the center of a magma chamber, promoting the development of a central vent system. But the location and orientation of the dikes may be also controlled by the shape of the edifice, or by the presence of scarps along the volcano slopes, commonly produced by sector collapses. Therefore, while dike propagation in areas without prominent relief is usually controlled by regional tectonism, the propagation of dikes in volcanic edifices depends upon the shape and topography of the edifice, as well as the stress conditions within shallow magma reservoirs.