Chapter 6: Volcanoes
Chapter 6: Volcanoes GEOL 1005
Popular in Environmental Geology
Popular in Geology
This 3 page Class Notes was uploaded by Kerrigan Unter on Monday October 19, 2015. The Class Notes belongs to GEOL 1005 at George Washington University taught by Brown, C in Summer 2015. Since its upload, it has received 23 views. For similar materials see Environmental Geology in Geology at George Washington University.
Reviews for Chapter 6: Volcanoes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/19/15
GEOL 1005 Chapter 6 Volcanoes 61 Volcano Basics Volcanoes places where molten rock rises from great depths to the uppermost levels of the crust and onto the surface Magma contains dissolved gases such as water vapor carbon dioxide and sulfur dioxide Active volcanic activity A new eruption occurs only when fresh magma reaches the surface Dormant volcanoes volcanoes that erupted thousands of years ago but still are capable of erupting in the future Volcanologists volcano scientists Viscosity magma s resistance to ow caused by temperature and composition Composition has a great in uence on magma viscosity than temperature does Silica makes magma more viscous Rapid release of gases from magma causes violent eruptions Shield volcanoes wide and gently sloping with a shape similar to a shield formed from mafic magma Fissures long cracks Lava tubes roofed conduit that lava ows through from an erupted vent to a depositional site Flood Basalt basaltic lavas that occur as vast accumulations of horizontal ows erupted from fissures in rapid succession over large areas Cinder cones feature where mafic magma erupt erupt at shield volcanoes ood basalt areas and stratovolcanoes Cinder cone eruptions are not large or explosive enough to send magma ying farther than the immediate vicinity of the vent typically short lived Stratovolcanoes take the shape of towering steepsloped and frequently symmetrical mountains composite volcanoes constructed of complexly alternating layers of lava and other volcanic debris can erupt explosively composed of intermediate to felsic magma Pyroclastics volcanic materials erupted into the atmosphere tephra Ash small crystals rock fragments and bits of glassy frozen magma Pumice glassy solidified magma that contains abundant gass bubbles Pyroclastics consist of fragments of various sized including ash ember pumice and great blocks of rock Felsic magmas are too viscous to ow easily Domes mounds or masses that plug volcanic vents Calderas large circulartooblong depressions that for When magma chambers erupt their contents and the volcanic mountain above them collapses into the empty magma chamber Magma chamber reservoir of magma in the shallow part of the lithosphere from Which volcanic materials are derived Calderaforming eruptions can be huge Tuff volcanic ash that becomes lithified Volcanic Explosivity Index VEI used to compare one eruption to another index number from 0 to 8 based on the volume of material ejected by past eruptions the height of the eruption column the style of eruption and how long the eruption lasted 62 Volcanoes Where and Why About 26 of the total magma erupted on Earth is generated at subduction zones Groundwater is also the source of water in hot springs and geysers around volcanoes Intraplate volcano far from any plate boundary unrelated to subduction or sea oor spreading process Hot spots local anomalies in the mantle places Where voluminous mantle material rises and melts to form mafic magma Fertile mantle When materials melt even While in the mantle and large amounts of mafic magma are produces 63 Volcanic Hazards Typical eruption sequence Hot gassy magma rises into the roots of the volcano A blockage below the vent prevents gas boiling out of the magma from escaping The pressure builds and the volcano adjusts small earthquakes and surface doming are evidence if the trapped magma The building pressure overcomes the strength of the confining rocks in a violent throatclearing explosion opens the vent and discharges a mass of debris and ash A mix of hot gases and ash rises its internal heat enabling it to climb higher and higher riding highaltitude winds ash in this eruption column can travel for hundreds or even thousands of kilometers Ash can smother whole communities Erupted ash can travel through the atmosphere for days and journey around the world Pyroclastic ows among the most deadly and destructive hazards of stratovolcanoes hot gases ash and other solid debris cascade down the anks of the volcano smashing or incinerating everything in its path Pyroclastic surge envelope of hot gas and ash Lahar wet debris ow originating on the anks of a volcano slurry of ash lava debris water soil rocks and trees Pahoehoe the hottest mafic lava that ows the fastest smooth ropey or wrinkled Aa viscous lava that erupts at lower temperatures rough blocky surface Acid rain cooling of the planet temporarily other global climate effects 64 Living with Volanoes Field volcanologists who work on active or erupting volcanoes are a small group Hazard assessment information about the degree of hazard from living near a volano Satellites that can detect concentrations of heat or ash plumes are increasingly used to monitor remote or inaccessible volcanoes
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'