Lithospheric displacement features on Europa and their interpretation

Persistent Link:
http://hdl.handle.net/10150/282707
Title:
Lithospheric displacement features on Europa and their interpretation
Author:
Tufts, Bruce Randall, 1948-
Issue Date:
1998
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:
A geologic study of lithospheric displacements on the Jovian moon Europa reveals lateral motions and plate flexure. Tectonics are governed by the rotation rate, nature of the lithosphere and underlying decoupling layer, the nature and causes of lateral displacements, plus mechanisms for creating and consuming surface area, and for restoring lithospheric rigidity. Astypalaea Linea is an 810-km-long strike-slip fault near the south pole, with 42 km of right-lateral offset, and includes a large pull-apart. Considering scale and contaminants, the lithosphere may have a tensile strength of ∼2.5 bars. The fault probably formed as a crack due to stresses from nonsynchronous rotation and diurnal tides, and was displaced by "walking" due to diurnal tides. Adjacent regional structures record earlier episodes of strike-slip. Wedge-shaped bands in the antijovian fracture zone are reconstructed, confirming the occurrence of block rotation and episodic dilation. A band on the leading side of the satellite is also reconstructed. Whether these bands formed under the influence of the same stress patterns which caused Astypalaea Linea is unclear; regional structures in the antijovian region suggest deformation by distributed shear. Dilation has also occurred across at least one ridge representative of a type independently interpreted as dilational based on ridge morphology. Other ridges apparently flex the underlying lithospheric plate downward. The lithosphere is inferred from flexural parameters at one locality to be 0.25-3.5 km thick. New lithosphere forms by ratchet-type spreading at bands and some ridges. Surface area may be removed by chaos formation or other processes. A global time marker based on a shift in ridge size is used to show that displacement was probably long-lived as well as widespread. During displacement, lithospheric plates were rigid and integral despite the appearance of cracks, perhaps due to annealing processes. Tides are the primary driving force for Europan tectonics and have produced a complex geologic history, consistent with Greenberg et al. (1997). A subsurface ocean, maintained by tidal heating, probably existed at the time of the displacements, which are relatively recent, and may well exist today.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Geology.; Physics, Astronomy and Astrophysics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Geosciences
Degree Grantor:
University of Arizona
Advisor:
Baker, Victor R.; Greenberg, Richard J.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleLithospheric displacement features on Europa and their interpretationen_US
dc.creatorTufts, Bruce Randall, 1948-en_US
dc.contributor.authorTufts, Bruce Randall, 1948-en_US
dc.date.issued1998en_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.abstractA geologic study of lithospheric displacements on the Jovian moon Europa reveals lateral motions and plate flexure. Tectonics are governed by the rotation rate, nature of the lithosphere and underlying decoupling layer, the nature and causes of lateral displacements, plus mechanisms for creating and consuming surface area, and for restoring lithospheric rigidity. Astypalaea Linea is an 810-km-long strike-slip fault near the south pole, with 42 km of right-lateral offset, and includes a large pull-apart. Considering scale and contaminants, the lithosphere may have a tensile strength of ∼2.5 bars. The fault probably formed as a crack due to stresses from nonsynchronous rotation and diurnal tides, and was displaced by "walking" due to diurnal tides. Adjacent regional structures record earlier episodes of strike-slip. Wedge-shaped bands in the antijovian fracture zone are reconstructed, confirming the occurrence of block rotation and episodic dilation. A band on the leading side of the satellite is also reconstructed. Whether these bands formed under the influence of the same stress patterns which caused Astypalaea Linea is unclear; regional structures in the antijovian region suggest deformation by distributed shear. Dilation has also occurred across at least one ridge representative of a type independently interpreted as dilational based on ridge morphology. Other ridges apparently flex the underlying lithospheric plate downward. The lithosphere is inferred from flexural parameters at one locality to be 0.25-3.5 km thick. New lithosphere forms by ratchet-type spreading at bands and some ridges. Surface area may be removed by chaos formation or other processes. A global time marker based on a shift in ridge size is used to show that displacement was probably long-lived as well as widespread. During displacement, lithospheric plates were rigid and integral despite the appearance of cracks, perhaps due to annealing processes. Tides are the primary driving force for Europan tectonics and have produced a complex geologic history, consistent with Greenberg et al. (1997). A subsurface ocean, maintained by tidal heating, probably existed at the time of the displacements, which are relatively recent, and may well exist today.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectGeology.en_US
dc.subjectPhysics, Astronomy and Astrophysics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBaker, Victor R.en_US
dc.contributor.advisorGreenberg, Richard J.en_US
dc.identifier.proquest9901669en_US
dc.identifier.bibrecord.b38806836en_US
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