Volcanoes. 11/25/2013. Geology 15 Lecture 27 VOLCANO!

Transcription

1 Hazard Update Surprise POP Review Tsunami Activity 10 B Today s Material Volcanoes Volcanic Hazards Geology 15 Lecture 27 VOLCANO! an erupting volcano create a newisland off the coast of japan Today s Material Volcanoes Volcanic Hazards Opera set for the eruption of Vesuvius from Pacini s The Last Day of Pompeii, about , Carlo Sanquirico after Alessandro Sanquirico. The Getty Research Institute Lava mapped in 17 th and 18 th centuries set for the eruption of vesuvius from map blog.com/wp content/uploads/2010/01/vesuv_mount_vesuvius.jpg 1

2 This Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image of Mt. Vesuvius, Italy was acquired September 26, 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. of art/eruption mt vesuvius 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 Pompeii. Pierre Jacques Volaire The Eruption of Mt. Vesuvius

3 Herculaneum list/ Hot Spots Rifts Subduction Zones World Map of Volcanoes, Earthquakes, Impact Craters, and Plate Tectonics 3

4 CASCADES VOLCANO! GEfk2p2 4

5 /img932.jpg eference.html jpg 5

6 Basalt is a hard, black volcanic rock with less than about 52 weight percent silica (SiO 2 ). 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

7 Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO 2 ). Andesite magma commonly erupts from stratovolcanoes as thick lava flows, some reaching several km in length. Andesite magma can also generate strong explosive eruptions to form pyroclastic flows and surges and enormous eruption columns. Andesites erupt at temperatures between 900 and 1100 C. Dacite lava is most often light gray, but can be dark gray to black. Dacite lava consists of about 63 to 68 percent silica (SiO2). It is one of the most common rock types associated with enormous Plinian style eruptions. When relatively gas poor dacite erupts onto a volcano's surface, it typically forms thick rounded lava flow in the shape of a dome. 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. 7

8 1/2 Fierstein APS V11 I1.pdf USGS VOLCANO! 8

9 Augustine Volcano in the Cook Inlet is a stratovolcano (or composite cone). This photograph was taken looking northwest; volcanic ash covers the upper flanks of the summit. White steam is being emitted. 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 km 3 (7 mi 3 ) of material in 60 hours. Falling Mountain, a lava dome truncated by the 1912 eruption, is visible behind the Novarupta dome; snow capped stratovolcano Mount Mageik can be seen 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) across and averages 500 m (1,640 ft) in depth. Voluminous post caldera eruptive activity has produced a wide variety of volcanic landforms and deposits within the caldera. The volcano is located in Aniakchak National Park and Preserve on the Alaska Peninsula. Mount Wrangell, a 4,317 m (14,163 ft) high andesite shield volcano on the right skyline, is the only volcano in the Wrangell Mountains with documented historical activity consisting of several minor, possibly phreatic eruptions in the early 1900s. At left is Mount Zanetti, a 3,965 m (13,009 ft) high cone. View is to the northeast. 9

10 Pyroclastic flow (deposits of volcanic ash, gas, and pumice flows) deposits on the southwestern flank of Augustine Volcano, Cook Inlet, Alaska. Fumarolic activity at the summit of Fourpeaked Volcano in Kamtai National Park and Preserve on the Alaska Peninsula 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 volcano. The rim of Katmai Caldera is on the skyline at left. 1/2 Fierstein APS V11 I1.pdf 1/2 Fierstein APS V11 I1.pdf 10

11 Watch Out for Those BOMBS Lassen Peak viewed from the south at the summit of Brokeoff Volcano 11

12 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 es/pglossary/vei.php Volcanic Hazard Mt. Lassen 12

13 Volcanic Hazard Crater Lake Volcanic Hazard Mt. St. Helens 13