Transcript volcanism
Read this on-line USGS publication at the URL http://pubs.usgs.gov/gip/volc Volcanoes of the World http://www.volcano.si.edu/gvp/volcano/index.htm#regions Volcanism occurs ... at the plate margins ... at divergent boundaries, as the sea floor spreads, e.g., the spreading submarine ridges and rises; and at the subducted margins of convergent plate boundaries ... when the oceanic edge of one plate collides against the oceanic edge of another plate, so forming an island arc, e.g., the Sunda Arc, the Philippines, or when the oceanic edge of one plate collides against the continental edge of another plate, e.g., the Cascade Range volcanism. at the hot-spots or mantle-plumes, as the HawaiiEmperor chain, Iceland, Azores, Yellowstone etc., and as the flood basalts or Large Igneous Provinces, e.g., CRB, Deccan, Parana, Siberian Traps etc. Sea floor spread by intermittant volcanism at the mid-ocean ridge (top left) results in the recording by subsequent lavas of the geomagnetic polarity reversals (left bottom) and the resulting marine magnetic anomalies can be mapped by the magnetometers towed by ships (bottom right). Map showing the Mid-Atlantic Ridge splitting Iceland and separating the North American and Eurasian Plates. The map also shows Reykjavik, the capital of Iceland, the Thingvellir area, and the locations of some of Iceland's active volcanoes (red triangles), including Krafla. The Mid-Atlantic Ridge, which splits nearly the entire Atlantic Ocean north to south, is probably the bestknown and moststudied example of a divergent-plate boundary. Lava fountains (5p;10 m high) spouting from eruptive fissures during the October 1980 eruption of Krafla Volcano. View of the first hightemperature vent (380 °C) ever seen by scientists during a dive of the deepsea submersible Alvin on the East Pacific Rise (latitude 21° north) in 1979. Such geothermal vents--called smokers because they resemble chimneys--spew dark, mineral-rich, fluids heated by contact with the newly formed, still-hot oceanic crust. This photograph shows a black smoker, but smokers can also be white, grey, or clear depending on the material being ejected. The deep-sea hot-spring environment supports abundant and bizarre sea life, including tube worms, crabs, giant clams. This hot-spring "neighborhood" is at 13° N along the East Pacific Rise. Plate boundaries can be either active, i.e., divergent versus or convergent, or passive (transform) Volcanism occurs at the subducted margins that form ... either by the convergence of oceanic edges of plates or by the convergence of continental edge of one plate and the oceanic edge of the other. A convergent plate boundary, e.g., the convergence of Nazca and South American plates Juan de Fuca ridge and the associated plates and plate boundaries off the Pacific Northeast and Canada. Note that the Cascadia subduction zone is also called the “Filled Trench”, as this trench got filled by sediments carried by the huge runoff from land that has characterized this region particularly since the Last Ice Age. Nintyeast Ridge The Hawaii-Emperor seamounts have evolved over the past ~65 Ma as the Pacific plate traversed a fixed mantle plume. (http://www.colorado.edu/geography/cartpro/cartography2/spring2001/campbell/final/anime_pg.html) Archaea Habitats: Rotorua, New Zealand For information on the LIPs on the internet, try http://www.ig.utexas.edu/research/projects/lips/lips.html Also visit the USGS volcanoe sites, starting with http://volcanoes.usgs.gov/ and the links provided there. Deccan traps, the ~106 km3 flood basalt province in peninsular India, extruded at or about the K/T boundary. Photograph by Lazlo Keszthelyi http://volcano.und.nodak.edu/vwdocs/Parks/hawaii/recent_events/dinosaurs.jpg http://www.etl.noaa.gov/review/aq/post/e.html Mt. Pinatubo: June 13, 1991 El Chichon, March 1982 Satellites tracked the spread of airborne sulfuric acid mist formed by SO2 from the 1991 eruption of Mt. Pinatubo, Phillippines 5/20-6/6/91 (before eruption) 7/4-7/10/91 (after circulating the earth) The two volcanoes had remarkably similar build-up El Chicon Mt. Pinatubo Aerosol loading before and after Mt. Pinatubo's eruption. Note the simultaneous increase in tropospheric and stratospheric loading. Tropopause folds seasonally purge lower sratospheric material into the troposhpere. The ratio between (separation of) ruby and CO2 backscatter coefficients indicates the median size of sulfuric acid aerosol particles. But their decay phases were notably different El Chicon Mt. Pinatubo Mt. Pinatubo El Chicon Conclusion Multi-year, multi-wavelength lidar studies of two major volcanic events reveal details of buildup and decay that are important for proper climatic modeling of such events. Over the United States, build-up from these two tropical volcanoes appears to be similar but decay is dissimilar. Simultaeously, both the troposphere and the stratosphere are affected by such eruptions, a heretofore unknown result. http://www.etl.noaa.gov/review/aq/post/c.html Pinatubo eruption, June 15, 1991. This image was collected during the beginning of the 3-hourlong climactic eruption. The yellow X is the approximate location of the vent and the red outline is the coastline of the northern Philippines. (R. Holasek) http://geont1.lanl.gov/HEIKEN/one/atmosphere.htm Ice contact and Subglacial Volcanism http://perseus.geology.ubc.ca/projects/subglacial/ The worldwide distribution of sub-glacial volcanic deposits Iceland Alaska, British Columbia, Yukon and the Cascades Antarctica Andes Hawaii Lake Nyos, Cameroon Catastrophe at Lake Nyos, Cameroon On August 21, 1986, a massive cloud of CO2 gas from the lake flowed out over nearby towns and claimed 1,700 lives. The victims were not poisoned, the simply suffocated: being denser than air, CO2 would tend to settle near the ground and be rather slow to disperse.