New version page

ECU GEOL 1500 - Volcano Notes - Abbreviated - Geol 1500 - Fall 2014

This preview shows page 1-2-3-4-5 out of 15 pages.

View Full Document
View Full Document

End of preview. Want to read all 15 pages?

Upload your study docs or become a GradeBuddy member to access this document.

View Full Document
Unformatted text preview:

MAGMA AND LAVAA. Lava Flow –The term used for magma once it has erupted onto the Earth’s surfaceB. Pyroclastic Material or Tephra – Tephra is a general term for fragments of volcanic rockand lava regardless of size that are blasted into the air by explosions or carried upward by hot gases in eruption columns or lava fountainsand deposited from the air. When Ash-Sized Pyroclastic Material becomes lithified, it is called a Volcanic Tuff.Cinder Cone – A small, conical-shaped volcanic cone built entirely of loose pyroclastic materialmaterial, mostly cinder in size.Calderas – A large (at least a mile in diameter), circular to elliptical (map/aerial view), steep-walled depression that forms by collapse and subsidence after a major eruption. Primarily associated with Rhyolitic VolcanismCraters - Craters differ from calderas both in size, shape, and origin. Craters are much smaller features than calderas and are typically defined as being less than 1 km in diameter and are funnel-shaped. Although both craters and calderas are most often associated with explosive eruptions, craters are typically formed by the explosive ejection of material in and surrounding the upper part of the conduit, rather than by collapse.Volcanic Dome or Lava Dome– A steep-sided mound that forms when viscous, doughy lava piles upnear a volcanic vent. Domes are formed primarily by Rhyolitic lavas.VOLCANISM AND VOLCANIC LANDFORMSINTRODUCTIONA Volcano is a vent in the surface of the Earth through which magma and associated gases and pyroclastic material erupt and the conically-shaped landform that is produced by ejected material.Cartoon of a Volcano as Cone-shaped Landform and a Vent SystemVolcanic Cone as a LandformVolcanism may occur as: (A) Lava flows primarily from a central vent, but sometimes from flank vents and from volcanic cones; (B) Explosive eruptions of dust, ash, cinders, and blocks (tephra/pyroclastic material) usually from a volcanic cone; and (C) Lava flows from fissures that form extensive, broad plateaus or plains of lava flows. Central Vent Eruption Pyroclastic Eruption, Unzen, JAPAN Michoacán-Guanajuato, MEXICO Fissure Eruption,Krafla, ICELAND Fissure Eruption, Tolbachik, RUSSIAMAGMA AND LAVAMagma is molten rock, together with suspended crystals and dissolved gases, that form when temperatures rise sufficiently high for melting to occur in the crust and upper mantle. Most magmais a mixture of liquid (melt) and crystals and a small percentage of dissolved gases. Lava is magma that is erupted at the Earth’s surface from a volcanic cone or fissure. Hence, Magma becomes Lava as it is extruded onto the Earth’s surface. Lava Flow22Types of Materials Erupted from Volcanoes and FissuresA. Lava Flow –The term used for magma once it has erupted onto the Earth’s surface Basaltic Lava Flow at Valley of the Fires near Carrizozo, NMThis is the youngest lava flow in the lower 48 states of USA1. a. Pahoehoe Lava Flow - Smooth, ropy, very low viscosity lava flow.33Pahoehoe Lava Flow, Hawaii Pahoehoe Lava Flow, Hawaii2. b Aa Lava Flow - Angular, jagged, blocky, more viscous lava flow. Aa Lava Flow, Hawaii44B. Pyroclastic Material or Tephra – Tephra is a general term for fragments of volcanic rock and lava regardless of size that are blasted into the air by explosions or carried upward by hot gases in eruption columnsor lava fountainsand deposited from the air. When Ash-Sized Pyroclastic Material becomes lithified, it is called a Volcanic Tuff.The Bandelier Volcanic Tuff1. Comes in all sizes - dust, ash, lapilli/cinders, and bombs/blocks Volcanic Ash Volcanic Lapilli Volcanic Block Volcanic BombC. Gases - H2O, CO2, SO2, CO, H2S, H2, CH4, Acids (HCl and HF), CyanidesCLASSIFICATION OF VOLCANIC LANDFORMS, 55From the USGS Volcano WebsiteShield Cones – A gently sloping volcano that is built almost exclusively of lava flows, Which are entirely basaltic in composition.66Sierra Grande, Capulin Volcanic Field, NE New MexicoPrestahnukur, ICELANDComposite Cones or StratoVolcanoes – A steep-sided volcano composed of both lava flows (andesite and basalt) and pyroclastic material.77Fujisan, JAPAN Mayon, PHILIPPINESCinder Cone – A small, conical-shaped volcanic cone built entirely of loose pyroclastic material material, mostly cinder in size.Cerro Negro, Guatamala88Michoacán-Guanajuato, MEXICOCalderas – A large (at least a mile in diameter), circular to elliptical (map/aerial view), steep-walled depression that forms by collapse and subsidence after a major eruption. Primarily associated with Rhyolitic Volcanism993 Calderas that have formed in the Lake Toba Caldera (100 Km long) in past million years in the USA North Sumatra, INDONESIA (75,000 yrs BP)Valles Caldera (Valle Grande), North Central New MexicoMashu, JAPAN1010Craters - Craters differ from calderas both in size, shape, and origin. Craters are much smaller features than calderas and are typically defined as being less than 1 km in diameter and are funnel-shaped. Although both craters and calderas are most often associated with explosive eruptions, craters are typically formed by the explosive ejection of material in and surrounding the upper part of the conduit, rather than by collapse.Lengai, Ol Doinyo, KENYAVolcanic Dome or Lava Dome– A steep-sided mound that forms when viscous, doughy lava piles up near a volcanic vent. Domes are formed primarily by Rhyolitic lavas.Lava Dome in Mount St. Helens Crater1111Lava Dome at Merapi, INDONESIAFumarole - Volcanic Vent which emits gases; craters of many dormant volcanoes contain fumaroles.Fumaroles are also called, “Solfataras”.Fumaroles at Hakone Volcano-Caldera, JAPANSummary 1212“Volcano Types” <http://vulcan.wr.usgs.gov/Glossary/VolcanoTypes/volcano_types.html>PLATE TECTONIC SETTING VERSUS MAGMA TYPEThe compositional type of magma erupted from any volcano is ultimately controlled by its Plate Tectonic Setting. This setting dictates the type of materials that are being partially melted in the Asthenosphere. Therefore, sometimes volcanoes are classified by tectonic setting.I. Subduction Zone-type Convergent Boundaries – A zone of convergence of two tectonic plates, one of which overrides the other. A. Island Arc-Type Subduction Zone – Predominantly Andesite 1313B. Continental-type/Andean-Type Subduction Zone –


View Full Document
Loading Unlocking...
Login

Join to view Volcano Notes - Abbreviated - Geol 1500 - Fall 2014 and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Volcano Notes - Abbreviated - Geol 1500 - Fall 2014 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?