Basaltic Volcanic Fields

Basaltic volcanic fields consist of one or more volcanoes within a defined area that is separate from other volcanic areas and that has an internally consistent tectonic/structural setting. Most of the volcanoes are monogenetic, each having only a single eruptive episode lasting from weeks to decades before becoming extinct, and are of small volume (typically around 1 km3 or less). These volcanoes share many eruptive processes with larger, polygenetic volcanoes of basaltic composition, including Strombolian, Hawaiian, and phreatomagmatic explosive activity and effusion of lava flows. They form a range of landformsincluding lava fields, scoria cones, small shields, maars, tuffcones, and tuff rings depending upon the dominance of magmatic volatiles versus phreatomagmatic explosions in driving eruptions, and upon the magma volume flux and processes within the shallow crust. Basaltic volcanic fields typically contain volcano alignments that may be related to crustal structures, and clusters of high spatial vent density that are likely related to variability in the upper mantle magma sources. Hazard assessment is complicated by the many factors that affect the timing and locations of successive eruptions within a volcanic field. Recent research on magma sources and ascent for monogenetic volcanoes suggests an important role for compositional heterogeneity in the upper mantle, and that volatile fluxes during eruptions can be of similar magnitude as at larger polygenetic volcanoes