Vents in the surface of the Earth through which magma and associated gases erupt; also, the forms or structures, usually conical, that are produced by the erupted material. [Glossary of Geology, 4th ed.]
Overview of volcano hazards in California with links to monitoring data including earthquakes and deformations, long-term outlook, volcano hazards in the area, USGS response plan, image gallery, monitoring and topical studies, publications and references.
Visual monitoring of volcanoes by closed-circuit television and video monitoring for a permanent video record of events using slow-scan television which permits continuous surveillance at a distance for remote volcanoes or in times of danger.
Volcano Watch is a weekly newsletter issued by the U.S. Geological Survey's Hawaiian Volcano Observatory on volcanic features on the Big Island, volcanic hazards, and informational topics of Long Valley, Montserrat, or Alaska.