Thesis (Ph.D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 236-252).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographical references (leaves 38-41). Also available on the World Wide Web.

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

No description available.

Thesis (Professional Degree)--University of Missouri, School of Mines and Metallurgy, 1929. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed October 7, 2009) Includes bibliographical references (p. 20) and index (p. 21-22).

Thesis (M.S.)--Brigham Young University. Dept. of Geological Sciences, 2008. / Includes bibliographical references (p. 53-57).

Thesis (Ph. D.)--University of Rhode Island, 2004. / Typescript. Includes bibliographical references (leaves 263-280).

No description available.

This research involves a study of a 2 km thick volcanic succession which accumulated during the opening stages of the precursor of the Reykjanes-Langjökull axial rift zone in W-Iceland, between 6-3 m.y. Following the initial accumulation of olivine tholeiite lavas, which lie unconformably on an older crustal basement 10-13 m.y.), a central volcano developed in the Hafnarfjall-Skarðsheiði area. It was active for some 1.5 m.y. and consists of four volcanic phases: I. The Brekkufjall phase is characterized by basaltic volcanism followed by voluminous and copious extrusions of differentiated rocks culminating in a sudden caldera collapse (c.5 km wide) in Brekkufjall. II. During the Hafnarfjall phase a thick extrusive sequence of basaltic to rhyolitic compositions accumulated, mainly fed by ENE fissures. During the gradual subsidence of the Hafnarfjall caldera (7 by 5 km) a marked decrease occurred in lava accumulation rate outside the caldera. Epicentres of three cone sheet swarms coincide in time and space with three basinal structures of this caldera. III. The Skarðsheiði phase is characterized by N-S fissuring and a marked bimodal basalt-rhyolite lava accumulation. IV. Remnants of the Heioarhorn phase include compositions ranging from basalts to rhyolites. The western boundary of the axial rift zone is marked by large intrusives, basalt flexuring, a sheet swarm and the disappearance of dyke swarms. The lenticular unit was later buried by lavas of the Hvalfjörður lenticular unit. Rocks of the central volcano follow the Þingrmúli trend, but is discontinuous in the basal tic andesite range. Basalts (frequently porphyritic) with relatively monotonous compositions and low LIL abundancies predominate during episodes of low extrusion rate whereas high elemental dispersion characterizes basalts of high extrusion rate episodes. The basalt compositions are believed to be controlled more by partial melting processes rather than by episodes of low-pressure fractionation. The differentiated rocks are considered to have predominantly formed by partial melting of the lower crust.