Textbook Notes (363,091)
Canada (158,185)
ERTH 2415 (21)
Chapter 8

Chapter 8 summary.doc

13 Pages
Unlock Document

Carleton University
Earth Sciences
ERTH 2415
Claire Samson

Summary of Chapter 8Volcanism at Spreading CentresMost of the volcanism of Earth takes place along the oceanic ridge systems where seafloor spreading occursSolid but hot and ductile mantle rock rises upward into regions of lower pressure where up to 30 to 40 of the rock melts and flows as basaltic magmaVirtually all of this volcanic activity takes place below sea level and is thus difficult to viewIn 1979 the submersible Alvin gave scientists a first glimpse at the newly formed still hot oceanic crust on the seafloor Alvins photographs unveiled hightemperature ventscalled black smokers because they resemble chimneysspewing dark mineralrich fluids and surrounded by a thriving ecosystem with abundant lifeforms Sunlight does not reach these organisms which rely on the chemical reactions associated with hydrothermal fluids for energyThe study of these extremophiles gives biologists clues about the different environments that might support extraterrestrial lifeThe worldwide rifting process releases enough magma to create 20km3 of new basaltic oceanic crust each yearThe volume of magma released by volcanic mountains is small compared to that of spreading centresIceland Is a volcanic plateau built of basaltic lava erupted from a hot spot below the midAtlantic spreading centreAbout 13 of the countrys surface is covered by glaciers and onethird comprises active volcanoesMost Icelandic eruptions do not cause deaths but exceptions do occurLava Flows of 1973The 1973 eruptions on the island of Heimaey on the southern coast of Iceland illustrate the peaceful nature of these eruptions The town of Vestmannaeyjar is built next to the premier fishing port in IcelandOn 23 January 1973 a fissure opened up only 1 km from the town of 5300 peopleBy early July the eruption had emitted 230 million m3 of lava and 26 m3 of pyroclastic materialThe lava flows increased the size of the island by 20Summary of Chapter 8Gases vented during the eruptive sequence other than water vapor were dominantly CO2 with lesser amounts of H2 CO and CH4The only fatality was a person asphyxiated in a gasfilled buildingVolcanism at Subduction ZonesVolcanism at subduction zones have the biggest impact on humansAlso because these volcanoes erupt directly into the atmosphere affecting weather worldwideIn Southern British Columbia where Canadas most explosive volcanoes are foundMount Garibaldi and Mount Meager at the northern end of a volcanic belt extending along the Pacific coast all the way to Northern California the Cascade RangeCascade Range Southern British Columbia and Northwestern United StatesThe plate tectonic process responsible for these volcanoes is identical to the cause of the regions great earthquakessubductionthe melting of part of the asthenosphere wedge above the subducting plate is aided by water released from sediment on top of the subducting plate49 eruptions have been documented in the Cascade range in the last 4000 years The slopes near a volcano reveal the remains of trees knocked down by volcanic blastsThese trees may be buried by volcanic ash incorporated in lahars or otherwise preserved Radiocarbon determinations of the dates when trees died also tell the dates of the volcanic eruptions that killed themVolcanoes built above hot spots also line up for example HawaiiMount St Helens Washington State 1980In late March 1980 Mount St Helens awoke from a 123yearlong slumberdozens of magnitude 3 earthquakes occurred each day as magma pushed its way toward the surfaceOn march 27 small explosions began as groundwater and magma came in contactAt 832 am on May 18 1980 the volcano blew off the top 400 m of its cone during a spectacular blast that generated about 100 times the power of all electrical power plants in the United States combinedFirst Mount St Helens achieved its beautiful conical shape during the mid1800sIn 1843 a SiO2rich lava dome grew at the volcano peak
More Less

Related notes for ERTH 2415

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.