Persistent Link:
http://hdl.handle.net/10150/186601
Title:
The gravitational potential energy of the Earth's lithosphere.
Author:
Coblentz, David Dwight.
Issue Date:
1994
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
This dissertation explores the tectonic implications of lateral potential-energy variations within the Earth's lithosphere. The central hypothesis of this study is that much of the observed intraplate-stress field is explainable in terms of these variations. The study develops the concept of a tectonic reference state (TRS), defined here as the mean potential energy of the lithosphere, Ū₁. A simple, first-order lithospheric density model is used to calculate Ū₁, which was found to correspond to both near-sealevel continental lithosphere and cooling oceanic lithosphere at a depth of 4.3 km. Although the potential energy of the continental lithosphere with elevated topography is sensitive to the assumed crustal density, ρ(c), both global- and plate-scale TRS values were found to be robust. A finite element analysis of the intraplate stress field in the African, South American and Indo-Australian plates was used to demonstrate that many of the long-wavelength features in the intraplate stress fields of these plates can be explained in terms of lateral variations in the lithospheric potential energy. Constraints for the numerical modeling were provided by an analysis of the long-wavelength trends in the intraplate stress field and a study of the intraplate stress magnitude in the South American plate. It was found that the value of Ū₁ changes significantly in response to the aging of oceanic lithosphere such that continental regions become increasingly susceptible to extensional collapse as the plate ages. In the case of the African and Antarctic plates, the aging of the ocean lithosphere since the late Jurassic has contributed a mean stress difference of about 5 MPa and 7.5 MPa (averaged over a 125km-thick lithosphere) in the respective continents. This extensional stress may contribute as much as 50% of cumulative force needed to deform continental lithosphere. One important implication of this calculation is that rifting in present-day continents and the breakup of supercontinents may be explained in terms of the time-evolution of the potential-energy distribution.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic.; Geophysics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Richardson, Randall M.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleThe gravitational potential energy of the Earth's lithosphere.en_US
dc.creatorCoblentz, David Dwight.en_US
dc.contributor.authorCoblentz, David Dwight.en_US
dc.date.issued1994en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThis dissertation explores the tectonic implications of lateral potential-energy variations within the Earth's lithosphere. The central hypothesis of this study is that much of the observed intraplate-stress field is explainable in terms of these variations. The study develops the concept of a tectonic reference state (TRS), defined here as the mean potential energy of the lithosphere, Ū₁. A simple, first-order lithospheric density model is used to calculate Ū₁, which was found to correspond to both near-sealevel continental lithosphere and cooling oceanic lithosphere at a depth of 4.3 km. Although the potential energy of the continental lithosphere with elevated topography is sensitive to the assumed crustal density, ρ(c), both global- and plate-scale TRS values were found to be robust. A finite element analysis of the intraplate stress field in the African, South American and Indo-Australian plates was used to demonstrate that many of the long-wavelength features in the intraplate stress fields of these plates can be explained in terms of lateral variations in the lithospheric potential energy. Constraints for the numerical modeling were provided by an analysis of the long-wavelength trends in the intraplate stress field and a study of the intraplate stress magnitude in the South American plate. It was found that the value of Ū₁ changes significantly in response to the aging of oceanic lithosphere such that continental regions become increasingly susceptible to extensional collapse as the plate ages. In the case of the African and Antarctic plates, the aging of the ocean lithosphere since the late Jurassic has contributed a mean stress difference of about 5 MPa and 7.5 MPa (averaged over a 125km-thick lithosphere) in the respective continents. This extensional stress may contribute as much as 50% of cumulative force needed to deform continental lithosphere. One important implication of this calculation is that rifting in present-day continents and the breakup of supercontinents may be explained in terms of the time-evolution of the potential-energy distribution.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academic.en_US
dc.subjectGeophysics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairRichardson, Randall M.en_US
dc.contributor.committeememberBeck, Susan L.en_US
dc.contributor.committeememberJohnson, Roy A.en_US
dc.identifier.proquest9424935en_US
dc.identifier.oclc722384711en_US
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