11/25/2013 Geology 15 Lecture 27 VOLCANO! http://motherboard.vice.com/blog/watch‐an‐erupting‐volcano‐create‐a‐new‐ • Hazard Update island‐off‐the‐coast‐of‐japan • Surprise POP • Review • Tsunami • Activity 10 B • Today’s Material • Today’s Material • Volcanoes • Volcanoes • Volcanic Hazards • Volcanic Hazards http://volcanoes.usgs.gov/ Opera set for the eruption of Vesuvius from Pacini’s “The Last Day of Pompeii,” about 1827–32, Carlo Sanquirico after Alessandro Sanquirico. The Getty Research Institute Lava mapped in 17th and 18th centuries http://thegetty.tumblr.com/post/31429806008/opera‐set‐for‐the‐eruption‐of‐vesuvius‐from http://www.getty.edu/art/exhibitions/pompeii/index.html http://www.old‐map‐blog.com/wp‐content/uploads/2010/01/Vesuv_Mount_Vesuvius.jpg 1 11/25/2013 This Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image of Mt. Vesuvius, Italy was acquired September 26, 2000. The false‐color image covers an area of 36 by 45 km. Vesuvius overlooks the city of Naples and the Bay of Naples in central Italy. (Popocatepetl and Mount Fuji are other volcanos surrounded by dense urban areas.) In 79 AD, Vesuvius erupted cataclysmically, burying all of the surrounding cites with up to 30 m of ash. The towns of Pompeii and Herculanaeum were rediscovered in the 18th century, and excavated in the 20th century. They provide a snapshot of Roman life from 2000 years ago: perfectly preserved are wooden objects, food items, and the casts of hundreds of victims. Vesuvius is intensively monitored for potential signs of unrest that could signal the beginning of another eruption. http://earthobservatory.nasa.gov/IOTD/view.php?id=1045 Herculaneum AD 79. A large number of people were sheltering in this seaside boathouse. The ancient Roman town was destroyed by the same Mt. Vesuvius eruption that took out Pierre‐Jacques Volaire The Eruption of Mt. Vesuvius Pompeii. http://artnc.org/works‐of‐art/eruption‐mt‐vesuvius 1777 https://www.pinterest.com/pin/470978073501952619/ 2 11/25/2013 Herculaneum http://www.roughguides.com/article/bucket‐list/ http://earth.rice.edu/mtpe/geo/geosphere/hot/volcanoes/volcanoes_b2.html http://www.geog.ucsb.edu/~dylan/mtpe/geosphere/wh/vol/volcanoes.html • Hot Spots • Rifts • Subduction Zones World Map of Volcanoes, Earthquakes, Impact http://pubs.usgs.gov/imap/2800/ Craters, and Plate Tectonics 3 11/25/2013 CASCADES VOLCANO! https://www.youtube.com/watch?v=forP1N1XwYE&list=TLiRzlzR8ACBsqdIN3pN4JNGUH‐GEfk2p2 http://www.geog.ucsb.edu/~dylan/mtpe/geosphere/wh/vol/volcanoes.html 4 11/25/2013 http://www.geog.ucsb.edu/~dylan/mtpe/geosphere/wh/vol/volcanoes.html http://volcanoes.usgs.gov/vsc/images/image_mngr/900‐999/img932.jpg http://vulcan.wr.usgs.gov/Glossary/VolcanoTypes/volcano_types_quick_r http://vulcan.wr.usgs.gov/Glossary/VolcanoTypes/volcano_types.html eference.html http://bc.outcrop.org/images/rocks/igneous/press4e/figure‐05‐03.jpg 5 11/25/2013 http://bc.outcrop.org/images/rocks/rocksmadeofminerals.jpg http://volcanoes.usgs.gov/images/pglossary/VolRocks.php http://volcanoes.usgs.gov/images/pglossary/basalt.php Basalt is a hard, black volcanic rock with less than about 52 weight percent silica (SiO2). Because of basalt's low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava can flow quickly and easily move >20 km from a vent. The low viscosity typically allows volcanic gases to escape without generating enormous eruption columns. Basaltic lava fountains and fissure eruptions, however, still form explosive fountains hundreds of meters tall. 6 11/25/2013 http://volcanoes.usgs.gov/images/pglossary/andesite.php http://volcanoes.usgs.gov/images/pglossary/dacite.php Andesite is a gray to black volcanic rock with between about 52 and 63 Dacite lava is most often light gray, but can be dark gray to black. Dacite weight percent silica (SiO2). Andesite magma commonly erupts from stratovolcanoes as thick lava flows, some reaching several km in length. lava consists of about 63 to 68 percent silica (SiO2). It is one of the most Andesite magma can also generate strong explosive eruptions to form common rock types associated with enormous Plinian‐style eruptions. pyroclastic flows and surges and enormous eruption columns. Andesites When relatively gas‐poor dacite erupts onto a volcano's surface, it erupt at temperatures between 900 and 1100° C. typically forms thick rounded lava flow in the shape of a dome. http://volcanoes.usgs.gov/images/pglossary/rhyolite.php Rhyolite is a light‐colored rock with silica (SiO2) content greater than about 68 weight percent. Sodium and potassium oxides both can reach about 5 weight percent. Common mineral types include quartz, feldspar and biotite and are often found in a glassy matrix. Rhyolite is erupted at temperatures of 700 to 850° C. http://www.britannica.com/EBchecked/media/3256/ 7 11/25/2013 http://www.nps.gov/akso/nature/science/ak_park_science/PDF/2012Vol11‐1/2‐Fierstein‐APS‐V11‐I1.pdf http://bc.outcrop.org/GEOL_B10/lecture7.html USGS VOLCANO! 8 11/25/2013 Aerial view of 80‐m (260‐ft) high Novarupta, a blocky rhyolite (high silica) lava dome that marks the vent for the 1912 eruption that created the Valley of Ten Thousand Smokes in Katmai National Park and Preserve, Alaska. This eruption was the most voluminous on Earth in the 20th century, ejecting nearly 30 km3 (7 mi3) of material in Augustine Volcano in the Cook Inlet is a stratovolcano (or composite 60 hours. Falling Mountain, a lava dome truncated by the 1912 eruption, is visible cone). This photograph was taken looking northwest; volcanic ash behind the Novarupta dome; snow‐capped stratovolcano Mount Mageik can be seen covers the upper flanks of the summit. White steam is being emitted. at top of the photograph. Aerial view, looking east, of Aniakchak caldera. Formed during a catastrophic ash‐flow producing eruption about 3,400 years ago, Aniakchak caldera is about 10 km (6 mi) Mount Wrangell, a 4,317‐m (14,163‐ft) high andesite shield volcano on across and averages 500 m (1,640 ft) in depth. Voluminous post‐caldera eruptive the right skyline, is the only volcano in the Wrangell Mountains with activity has produced a wide variety of volcanic landforms and deposits within the documented historical activity consisting of several minor, possibly caldera. The volcano is located in Aniakchak National Park and Preserve on the Alaska phreatic eruptions in the early 1900s. At left is Mount Zanetti, a 3,965‐ Peninsula. m (13,009‐ft) high cone. View is to the northeast. 9 11/25/2013 Pyroclastic flow (deposits of volcanic ash, gas, and pumice flows) deposits on the southwestern flank of Augustine Volcano, Cook Inlet, Alaska. View southeast up the Valley of Ten Thousand Smoke from the Overlook Cabin in Katmai National Park and Preserve, Alaska. The valley has been filled with up to 200 m (660 ft) of pyroclastic flow deposits (ignimbrite) from the 1912 eruption of Novarupta Fumarolic activity at the summit of Fourpeaked Volcano in Kamtai volcano. The rim of Katmai Caldera is National Park and Preserve on the Alaska Peninsula on the skyline at left. http://www.nps.gov/akso/nature/science/ak_park_science/PDF/2012Vol11‐1/2‐Fierstein‐APS‐V11‐I1.pdf http://www.nps.gov/akso/nature/science/ak_park_science/PDF/2012Vol11‐1/2‐Fierstein‐APS‐V11‐I1.pdf 10 11/25/2013 Watch Out for Those BOMBS Lassen Peak viewed from the south at the summit of Brokeoff Volcano 11 11/25/2013 Bumpass Hell, a hydrothermal area in Lassen Volcanic Park. The pools contain hot water that bubble and steam. Measuring and Monitoring the VOLCANO! Volcanic Explosivity Index http://volcanoes.usgs.gov/imag Volcanic Hazard Mt. Lassen es/pglossary/vei.php 12 11/25/2013 Volcanic Hazard Crater Lake Volcanic Hazard Mt. St. Helens 13.