VOLCANO TYPES of New Mexico Volcano Simple New Mexico How and Why It Erupts Type Drawing/Section Example • violent explosive and catastrophic eruption of glowing clouds of ash that flow away from the caldera (ash-flows or pyroclastic flows), due to very high gas content and very high silica magma in a very large magma chamber caldera • the roof of the extremely large, shallow magma chamber collapses during and after eruption (super volcano) • uplift (rebound) of the caldera floor over a long period of time to form Redondo Peak, Valles Caldera and even later eruptions of high silica, low gas content lava domes around the interior margin of the caldera • lava intrudes earlier lava and piles up at the vent, because very high silica magma makes the lava viscous dome • mostly non-explosive eruptions, due to low gas content magma • near-surface intrusions are formed when continued eruptions push into the pile Cerro La Jara, Valles Caldera, Jemez Mtns • many intermittent eruptions of different types over a long time period caused by changes in the magma composition • built by lava flows, ash, and domes from multiple conduits of intermediate to low composite viscosity due to medium to low silica and gas content magma • intermittent mudflows and landslides are interlayered with ash, lava flows. and broken rocks due to crumbly materials erupted on steep upper slopes Mount Taylor volcano cinder • single to multiple eruptions that extend over years to decades • moderately explosive eruptions of mafic (basaltic) composition, including lava flows, (scoria) due to moderate gas content and low silica magma • builds a small volcano of ash, cinder, and scoria (fragmented magma) that is commonly 0.6 to 1.2 miles (1-2 km) in diameter cone Cat Hills, Los Lunas • multiple eruptions of long lava flows from a central conduit over a moderately long time period shield • mostly non-explosive and fluid eruptions, due to low silica and low gas content magma • forms a low, broad volcano with some ash and cinder at the summit Cerro Verde volcano • single eruption of a long, fluid, large volume of mafic (basaltic) lava lava • mainly lava with little ash and cinder due to low gas • lava covers large area due to low viscosity and low silica magma flow • usually erupted in association with a small cinder cone source volcano McCartys lava flow, El Malpais • multiple violent steam-blast eruptions, due to the interaction of magma and groundwater or surface water maar • forms a crater with its floor below ground level that is surrounded by a low rim of ejecta composed of fragmented magma and surrounding rock Zuni Salt Lake crater • the near-surface interior of a small volcano that has experienced erosion of its exterior volcanic flanks • erosion leaves behind the hard crater fill (lava flows, ash, and cinder) and the neck near-surface, magma-filled throat or conduit of the original volcano Cabezon Peak, Rio Puerco volcanic neck • a large region over which volcanism is active over a time period from thousands to field of millions of years • many new eruptions from multiple conduits, rather than many eruptions from a single volcanic vent, due to small batches of magma that are generated and erupted from small cones different places within the region over time to form each individual volcano • consists of a concentration of varied types of small volcanoes, dominantly cinder (volcanic field) cones and their associated lava flows, but also some shield volcanoes and lava domes Raton-Clayton volcanic field Poster design, graphic, and photographs by L.S. Crumpler and Jayne Aubele. These are just a few of New Mexico’s volcanoes. For more information about the location of volcanoes in New Mexico go to poster no. 2, or go to “Volcanoes of New Mexico” at www.nmnaturalhistory.org/sci_volcanoes.html New Mexico Museum of Natural History and Science Imagenés de la historia natural, No. 3.