This is why YVO is investing in monitoring for potential signs of volcanic unrest in these states. An astronaut onboard the International Space Station took photos of Carrizozo Malpas, a large basaltic lava flow in central New Mexico. This is the inherent volcanic hazard in the southwestern U.S.-new eruptions can originate at unknown locations within broad areas of widely varying land use patterns.Įven though volcanic eruptions are comparatively rare in the American Southwest, the Four Corners states were host to numerous volcanic eruptions in the past 10,000 years and will experience volcanic activity in the future. This is the nature of monogenetic volcanic fields-eruption sites open for a single episode of activity, and subsequent eruptions can occur anywhere within the field. Future eruptions will not necessarily occur from the location of a previous vent. For a high resolution version of the image, click here. The locations of volcanic fields and individual volcanoes are dictated by zones of weak crust and areas of pre-existing magma storage. The Malpais, which are the 75 km-long black feature in the satellite image below, are basaltic lava flows, such as are being erupted today in Hawaii. Upon reaching the surface, magma can erupt as lava flows and cinder cones-for example, Sunset Crater, Arizona Dotsero, Colorado and the Carrizozo lava flow, New Mexico. Magma may also stall beneath the surface, melt surrounding rock, and accumulate in large reservoirs that can erupt very violently, as was the case over one million years ago at Valles caldera, New Mexico.įuture eruptions will occur, but not necessarily in the same spot as previous ones. As mantle material moves to shallower depths, the confining pressure drops. Magma continues to rise because it is more buoyant than surrounding crustal rock.

The low viscosity typically allows volcanic gases to escape without generating enormous. Therefore, basaltic lava can flow quickly and easily move >20 km from a vent. Because of basalts low silica content, it has a low viscosity (resistance to flow).

Rifting and extension cause the crust to fracture and thin, providing space for the mantle to rise upward. Basalt is a hard, black volcanic rock with less than about 52 weight percent silica (SiO2). These mid-continent volcanoes occur where the crust is thin due to the tectonic processes of rifting and extension. Most of these volcanoes are monogenetic, meaning that they only produced one eruptive episode that may have lasted for days to years. The volcanoes of the American Southwest include over forty volcanic fields containing about 1400 single volcanic vents that have erupted over the course of the past 2.5 million years. Sunset Crater, a basaltic cinder cone in the San Francisco Volcanic Field, Arizona, erupted in 1085 A.D.