nonvolcanic

Nonvolcanic refers to geological or geophysical phenomena that are not produced by volcanic activity. The term is used to distinguish processes, rocks, landscapes, and hazards that arise from tectonic, sedimentary, or erosional forces rather than from magma movement, eruption, or volcanic gas emissions.

In seismology, nonvolcanic earthquakes are those not associated with magma movement or volcanic plumbing. In volcanic regions, earthquakes may be volcanic or tectonic; nonvolcanic tremor can also occur and is characterized by low-frequency seismic signals not generated by explosions. Nonvolcanic seismicity can still produce significant ground shaking and hazards.

Nonvolcanic landforms include uplifted and folded mountain belts, eroded plateaus, sedimentary basins, and metamorphic terrains formed primarily by tectonic forces or surface processes. In contrast, volcanic landforms are shaped by lava flows, ash falls, and other products of eruption.

In hydrogeology and resource exploration, nonvolcanic basins or provinces are sedimentary or metamorphic regions not related to volcanic intrusions or erupted volcanism.

The term emphasizes contrast with volcanic activity; many regions contain both volcanic and nonvolcanic features, and the absence of volcanism is determined through geological evidence such as the lack of erupted rocks, volcanic ash layers, or intrusive igneous activity. When used in seismology, nonvolcanic does not imply absence of hazard, only that the activity is not directly driven by a volcanic source. See also volcanology, tectonics, seismology.