What volcanoes are…• An opening in the planet’s crust• Causes volcanic ashes and gases to escape• Found where plates are diverging or converging
Vulcanism • Magma is expelled onto the surface (still molten) • Magma solidifies on the surface • Magma solidifies far below the surface
Volcanism• Lava- magma that has departed and has contacted with the surface• Rock fragments• Solidified lava blobs• Ashes• Dust• Gas• steam
Distribution • About 550 active volcanoes • Surface and underwater eruptions • Associated with plate boundaries
Factors of an eruption• Surface crust strength• Pressure• Chemicals – Silica (SiO2) is believed to be the main source of very explosive eruptions – Low silica content usually produces more of a fluid explosion
Classifications• Large and steep• Lava flows, pyroclastics, hardened mud flow deposits• Both “quiet” and explosive eruptions• Examples: Mt. Fuji, Mt. Rainier, Mt. Shasta, Mt. Vesuvius, Mt. St. Helens
Classifications • Small and sometimes an irregular shape • Plug of lava that is covered by pyroclastics (frequently occurs in the crater of Composite Volcano) • Examples: Lassen Peak, Mono Craters
Classifications• Small and steep sided• May be composed of ash or cinder-sized pieces• Produces “quiet” and explosive eruptions• Examples: Paricutin, Sunset Crater
Other Classifications • Caldera- produced when volcano explodes and/or collapses • Volcanic Neck- small, sharp spire that rises abruptly above the surrounding land
Hazards• Lava Flows – Rarely cause loss of life – Does damage to the area around it – Either moves fast or slow – Flow on predictable paths
Hazards • Eruption Column and Clouds – Consists of pyroclastic material and gases – Volcanic ash and dust form a cloud – Volcanic bombs – Can damage crops and collapse buildings
Hazards• Pyroclastic Flows – Avalanche of hot gases, ash, and rock fragments – Also called nuée ardente – Burns and buries anything in its path
Hazards • Volcanic Mudflows – Caused by heavy rain or melting of snow and glaciers – Water combined with ash and pyroclastic flow – Fast-moving slurry of mud and boulders – Buries the valley floor – Also known as Lahars
Can it be prevented?• Unfortunately no, because it is a natural occurrence all we can do is be prepared for when a volcano blows its top.
Works CitedFisher, Richard V. "The Volcano Information Center." Volcano Information Center (VIC). Web. 07 Dec. 2011. <http://volcanology.geol.ucsb.edu/>.McKnight, Tom L., and Darrel Hess. "Chapter 14 The Internal Processes.“ Physical Geography: a Landscape Appreciation. Eighth ed. Upper Saddle River, NJ: Prentice Hall, 2005. Print.Topinka, Lyn. "CVO Menu - Volcanic Hazards, Features, and Phenomena.“ USGS Cascades Volcano Observatory (CVO). 30 Jan. 2003. Web. 07 Dec. 2011. <http://vulcan.wr.usgs.gov/Glossary/framework.html>."Volcano - Credo Reference Topic." Credo Reference Home. Web. 07 Dec. 2011. <http://www.credoreference.com/topic/volcano>."Volcano | Define Volcano at Dictionary.com." Dictionary.com | Find the Meanings and Definitions of Words at Dictionary.com. Web. 07 Dec. 2011. <http://dictionary.reference.com/browse/volcano>."Volcano." Wikipedia, the Free Encyclopedia. Web. 07 Dec. 2011. <http://en.wikipedia.org/wiki/Volcano>.