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Ingeology, aresurgent dome is adome formed by swelling or rising of acaldera floor due to movement in themagma chamber beneath it. Unlike alava dome, a resurgent dome is not formed by the extrusion of highly viscouslava onto the surface, but rather by the uplift anddeformation of the surface itself by magma movement underground. Resurgent domes are typically found near the center of very large open calderas such asYellowstone Caldera orValles Caldera, and in turn such calderas are often referred to as "resurgent-type" calderas to distinguish them from the more common (but much smaller) calderas found onshield volcanoes andstratovolcanoes.
The structure that makes a resurgent dome possible is a fracture zone made up of ring faults surrounded by concentric normal faults around the outside of the rings. During initial formation of the caldera these ring faults provide vents for ash-flow eruptions and are the point at which subsidence of the cauldron block occurs. Subsequent magma flows then push the cauldron block back up creating the dome.[1]
In the monitoring ofvolcanic hazards, resurgent domes are often intensively monitored, as an ongoing increase in elevation accompanied by seismic activity is certain evidence for magma rising beneath the surface.
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