An overview of recent (1988 to 2014) caldera unrest: Knowledge and perspectives

摘要: Calderas are among the most active and dangerous volcanoes. Caldera unrest is defined by enhanced seismicity, gravity changes, surface deformation, degassing. Although much caldera does not lead to an eruption, every eruption preceded episode. Therefore, proper description of forecast its possible outcome a timely challenging task. Here we review best known at calderas from 1988 2014, building on previous work proposing updated database. Where established, root cause for always magmatic; none was purely hydrothermal or tectonic. An interpretive classification invokes two spectra—compositional (mafic felsic) state magma conduits feeding reservoir(s) (from fully plugged, through semiplugged, open). Magma gas in open can rise erupt freely; semiplugged erupts less frequently yet still allows some escape; plugged allow neither nor escape. Unrest mafic subtler, pronounced, repeated, especially with systems, ensuring continuous, aseismic, moderate release magma. Plugged felsic infrequently, anticipated isolated, short seismically unrest. Semiplugged also infrequently restless over decades centuries, uplift, degassing and, longer-term, resurgence, suggesting repeated stalled intrusions. Finally, expected advances better understanding discussed.