The Geology of Volcanoes and Their Facies Models

Modern volcanoes and volcanic centres encompass a wide variety of morphological, physical, facies and stratigraphic characteristics, and duration of primary volcanic versus sedimentary or epiclastic processes. This leads to the development of general facies models, which are relevant for modern settings, and valuable guides for making meaningful geological reconstructions of ancient volcanic successions. Our discussion covers the full scale of volcanic landforms, ranging from small individual monogenetic scoria and pumice cones and phreatomagmatic maar-type volcanoes, to larger polygenetic volcanoes. These include marine basaltic shields that from their base on the seafloor represent some of the largest volcanoes on the planet, as well as eruptive vents for flood plateau and plains basalt provinces, stratovolcanoes both found in both continental and marine settings, and the largest silicic explosive caldera volcanoes. The latter are sometimes called “supervolcanoes” which are responsible for some of the biggest explosive eruptions recorded in geological history, resulting from structural caldera collapse and in some settings contributing to regional ignimbrite “flare-up” events. Moreover, the special case of marine silicic calderas is also considered. We also now recognise a number of more complex intermediate to silicic volcanic systems; these include “multiplex volcanoes” which have changed in character through their evolution, and other multi-vent centres that appear to occur in the absence of a large central cone structure, or conversely are not controlled by caldera collapse depressions. The remaining two sections are grouped into intra- or subglacial volcanoes (formed under ice and meltwater lakes), and mafic oceanic volcanic centres, namely, spreading ridges, plateaus, seamounts, and surtseyan tuff cones. We also introduce the reader to the economic significance of potentially prospective volcano types and their successions prior to their detailed description in Chap. 18 , as well as concluding with a summary of the potential hazards posed by different types of volcanoes.