Ringfaults

Ringfaults are circular or arcuate fault zones that encircle a central block, forming a ring of fractures around a subsided or uplifted center. They commonly occur in volcanic and tectonic settings, most notably during caldera collapse or large-scale subsidence. The ring faults bound the margins of calderas and often define the geometry of concentric fault blocks, sometimes with a central resurgent dome.

Formation and mechanics: In caldera-forming events, withdrawal or destabilization of a magma chamber reduces support for the crust, triggering roof collapse along a roughly circular set of faults. The resulting ring faults accommodate slip around the perimeter and create concentric blocks that may tilt toward or away from the ring. Subsequent tectonic stresses can reactivate segments as normal, reverse, or oblique faults, preserving the overall ring geometry over broad areas. Ring faults are frequently associated with hydrothermal systems, and their geometric arrangement can influence fluid flow and mineralization.

Geologic significance and examples: Ringfaults shape the morphology of calderas, channel drainage and groundwater flow, and influence the localization of ore deposits. They provide key information for reconstructing collapse sequences and crustal stress histories. Notable examples include the ring fracture system surrounding the Yellowstone Caldera and the prominent ring faults that bound the Valles Caldera in New Mexico. Similar circular fault architectures are documented in other caldera systems worldwide, such as Long Valley and Campi Flegrei, reflecting common processes of crustal failure, collapse, and resurgence.