A sagging-spreading continuum of large volcano structure

By pk byrne · 2013 · cited by 39 — volcano sagging and spreading are two gravity- ... structures related to volcano spreading are ... mic) and brittle (seismogenic) parts of the lith-.
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GEOLOGY | March 2013 | www.gsapubs.org 1INTRODUCTIONUnderstanding a volcano’s structural devel-opment is crucial for studies of volcanic hazard,eruption behavior, and lithospheric dynamics.Volcano sagging and spreading are two gravity-driven deformation processes that shape largevolcanoes on terrestrial planets over 10 1–106 yr.Volcano spreading occurs when the lateralweight gradient of an edifice causes its slow out-ward collapse along a basal décollement (Borgiaet al., 2000). Sagging results when a volcano’sweight down-flexes its underlying basement andlithosphere (e.g., Zucca et al., 1982).Structures related to volcano spreading arewell understood (cf. Borgia et al., 2000): foldsand thrusts occur at or beyond the edifice’s base,while normal faults and “leaf grabens” crosscutits fl anks (Fig. 1A). Structures formed by vol-cano sagging are less understood, but include anedifice-encircling trough, peripheral joints of gra-bens, a flexural bulge (e.g., Kervyn et al., 2010),and possibly ...