Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991. / Includes bibliographical references (p. 151-156). / by Joshua Michael Aaron Ryder Wurman. / Sc.D.

Thesis (Ph. D. in Geology)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2012. / "September 2012." Cataloged from PDF version of thesis. / Includes bibliographical references. / In this thesis use a variety of geological observations to address the record of Neogene crustal deformation in the Central Aegean region, thereby providing new constraints on the overall geometric and tectonic evolution of an extensional system that is largely governed by the dynamics of a retreating subducting slab. I document a newly-described low-angle normal fault, termed the Octonii Detachment, that accommodated NE-SW directed crustal extension and controlled the pattern of sedimentation within the Early to Middle Miocene Kymi-Aliveri basin. I date the basin fill using a combination of magnetostratigraphy and U/Pb zircon geochronometry. Through detailed mapping of the spatial variation in sedimentary facies within the basin, I relate the record of sedimentation to Middle Miocene extensional exhumation of the metamorphic core complexes exposed in the Cycladic archipelago. In contrast with models of supra-detachment basin development related to fragmentation of the upper plate by arrays of parallel normal faults, I deduce that sedimentation in the Kymi-Aliveri basin occurred in the synformal core of a large-scale, extension-parallel fold. These observations provide direct upper-plate constraints on the timing and kinematics of crustal extension in a region that has been dominated by observations of lower-plate metamorphic rocks. Through paleomagnetic measurement of vertical-axis rotations in Early Miocene through Pliocene basin sequences and associated volcanic rocks, I constrain the initiation of rapid clockwise rotation in Central Greece to post-Early Pliocene time, and infer that Central Greece underwent two pulses of very rapid clockwise rotation separated by a ~10 million year interval of no apparent rotation. This paroxysmal style of deformation contrasts strongly with previous models of long-term, slow rotation driven by gradual trench retreat. I propose a model for the Pliocene deformation of the External Hellenides based on published paleomagnetic data that invokes lateral segmentation of the thrust belt along spaced zones of right-lateral deflection without development of through-going faults at the surface. This analysis attempts to explain how right-lateral motion of an internally stable Aegean Sea block was accommodated between the Kephalonia transform fault and the western prolongation of the North Anatolian Fault. Finally, I use paleomagnetic measurements from a ~3.4 billion year old volcanic and sedimentary succession preserved in the East Pilbara terrane in Western Australia to show that Earth's climate and geomagnetic field geometry could have arisen in a modern form by this time, and that the two oldest well-preserved rock sequences on Earth could in fact be remnants of a single terrane. / by Kyle Edward Bradley. / Ph.D.in Geology

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, June 2008. / Cataloged from PDF version of thesis. "31 May 2007." / Includes bibliographical references (pages 125-128). / We quantify the mobility of alluvial river channels in order to better understand the relationship between channel mobility and fluvial environment. We analyze five analog experiments, performed between 2002 and 2007 at the Saint Anthony Falls Laboratory, for area-based change in river-channel plan form with time. These experiments isolate the effects of (1) sediment input and deposition, (2) base-level, and (3) bank cohesion on channel mobility. (1) In experimental deltaic environments with aggradation and sea-level rise in equilibrium, aggradation rates scale non-linearly with channel mobility. The channels in the experiment with the higher aggradation rate move more rapidly overall, but the channels in the experiment with slower aggradation are more mobile when both experiments are scaled by their respective aggradation rates. Lower aggradation rates result in lower slopes, causing the flow to be shallower and broader, and for more deposition to occur. These low slopes result in lower Froude number, allowing the formation of flow-depth-high ripples that divert the flow. (2) We study experiments in which base-level change was slow, rapid, and intermediate in terms of average channel mobility when base-level is constant. Channels in an experimental basin with rapid (12.2 mm/hr) aggradation are three times as mobile during base-level rise as during base-level fall. Channels in a cohesive delta experiment (producing significantly lower channel mobility) are 1.5 times as mobile during slow base-level rise (0.237 mm/hr) as during steady base level. Base-level change that is slow on an average channel mobility timescale has little to no influence on channel mobility. (3) Channels in an experimental system of noncohesive sediment are 6.5 times as mobile as channels with alfalfa (Medicago sativa) planted in the flume. / by Andrew D. Wickert. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmosphere and Planetary Sciences, 1988. / Includes bibliographical references. / by Kristine Holderied. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1986. / Microfiche copy available in Archives and Science / Includes bibliographies. / by Hélène Lyon-Caen. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2004. / "June 2004." / Includes bibliographical references (p. 59-61). / (cont.) representing Phoenix and its rural equivalent is presented through a comparison with estimated energy fluxes for Houston, TX. / This study has found significant evidence of the Urban Heat Island Effect (UHIE) in Phoenix, AZ using historic and recent (up to 2002) temperature records. First, an explicit indicator of UHIE was identified by the -0.148⁰F per year decrease of the diurnal temperature range (DTR). This was explained by an increasing trend of 0.190⁰F per year in mean minimum temperature while the mean maximum increased at a much slower pace of 0.042⁰F per year. This has manifested itself in a significant nighttime heat island. Second, the UHIE for Phoenix was estimated to contribute about 15 [plus-minus] 5% of total climate variability for this city. That is, only about, 85% of the DTR for Phoenix can be accounted for by natural variability. This was established by comparing the average historical climate record for Phoenix Sky Harbor International Airport and several nearby rural sites. In this analysis, Casa Grande National Monument, a national park 40 miles southeast of Phoenix, was chosen as the most appropriate rural site for application of a method to assess the Phoenix UHIE by trading space-for-time. Finally, the basic concepts for the development of an urban heat island model were outlined. Land use changes and the materials used to build infrastructure were determined to be the most significant factors in determining the magnitude of the Phoenix (and similar cities) UHIE. These materials effectively reduce surface albedo and emissivity, decrease latent heat release by lowering the water permeability of surfaces, and increase the storage heat flux due to greater surface area density and much larger thermal mass offsetting the lower specific heat capacity. Anthropogenic heat release is also a factor, but mainly in dense urban cities. The energy balance / by Ryan Merkin. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1984. / Microfiche copy available in Archives and Science. / Bibliography: leaf 62. / by Robert Kuklinski. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 22-24). / Sedimentary rocks of all ages abound with geostable lipids of microbial origin, but many biomarkers lack known organismal sources and clear environmental contexts. Here we used Rhodospirillum rubrum, a metabolically versatile, genetically tractable c-Proteobacterium, to explore the diversity of its non-polar terpenoids as a function of growth condition and growth phase. We analyzed the nonpolar fraction of lipids extracted from R. rubrum grown under aerobic, anaerobic, heterotrophic and phototrophic conditions and detected a variety of bicyclic, tricyclic, tetracyclic and pentacyclic triterpenoids, derived from the enzymatic cyclization of squalene and produced in amounts comparable to diploptene. Identified compounds included bicyclic polypodatetraenes, malabaricatriene, euphadiene, adianane, and fernene. Prior to this work, malabaricatriene was an "orphan" biomarker suspected to have a microbial origin, yet it lacked a proven source. We observed similar patterns of polycyclic terpenoids in other hopanoid-producing c-proteobacteria, including Zymomonas mobilis, Rhodopseudomonas palustris, and Rhodomicrobium vannielii. The presence and relative abundance of polycyclic triterpenoids in R. rubrum varied with the growth stage (exponential versus early stationary phase) and growth condition (photoheterotrophic versus photoautotrophic growth). Since R. rubrum's genome contains a single squalene-hopene cyclase gene, the array of triterpenoids produced by it and other c-proteobacteria likely evolves from this enzyme performing low-fidelity cyclization. The observed diversity of sedimentary triterpenoids might therefore result from a select few squalene-hopene cyclase enzymes operating with varying specificity under a range of physiological and environmental conditions, rather than reflecting a great diversity of squalene-hopene cyclases. / by Katherine Harris. / S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2007. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 31). / This paper describes the Atlantic Meridional Mode (AMM) and its influence on tropical storm activity in the North Atlantic Basin. The Atlantic Meridional Mode is the oscillating sea- surface temperature (SST) gradient anomaly between the Northern Hemisphere (NH) and Southern Hemisphere (SH) portions of the Tropical Atlantic Ocean (TAO). Synthetic data generated from computer simulations as well as actual reanalysis data from North Atlantic Basin tropical storms was examined. A moderate correlation exists between increased (decreased) North Atlantic tropical storm activity and the high (low) phase of the AMM. The AMM correlates more strongly with the duration and intensity of tropical storms than the frequency. Increased understanding about the AMM and its affects on tropical storm activity will lead to improved forecasting of tropical systems, which affect many human lives each year. / by Nicholas Loyd. / S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 34-35). / The ocean provides a dynamic, constantly changing environment for marine phytoplankton. Understanding the effects of these changes on phytoplankton assemblages is fundamental when trying to anticipate future responses of primary producer's community to long-term environmental changes. In this study, artificial perturbation experiments were successfully performed on natural assemblages of phytoplankton to simulate conditions consistent with ocean acidification and North Pacific Subtropical Gyre (NPSG) upwelling patterns. These experiments demonstrated the feasibility and value of such perturbations in studying phytoplankton responses to environmental forcing. / by Alan D. Foreman. / S.B.