Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2008. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 65-68). / Several dozen impact glasses from Lonar Crater, in Maharashtra, India, were analyzed for evidence of impact-generated paleofields, and possible motional remanent magnetization. Lonar Crater formed when a meteorite impacted a bed of Deccan Trap basalts. Upon impact, the basalt was super heated into a fluid melt that would have been ejected from the crater, moving at speeds that allowed the smaller pieces of basalt to cool in mid-air. These smaller pieces would have cooled instantaneously, and due to their ferromagnetic composition may have recorded the presence of an impact generated magnetic field. This paper focuses on analyzing several dozen basaltic glass samples from the perimeter of Lonar Crater that are considered to be some of the most plausible known terrestrial analogs to the lunar impact glasses. Lonar impact glasses could serve as a decent analogue to lunar tektites, although differences in their rotational NRM and grain size suggest that they may not be the best recorders of paleointensity. The impact glasses display clear evidence of a series of wild, directionally unstable magnetic moments when heated to temperatures in excess of 400 to 500°C that are not observed in other terrestrial samples. The simplest explanation for this unusual behavior is that these randomized magnetic moments are the result of the progessive removal of different magnetization moments that had, up until the higher temperatures, been blocked in. Upon their removal, these randomized high temperature moments were revealed. Based on the NRM/sIRM ratios of the splash-form spherules the glasses slightly underestimate the intensity of the field in which they cooled. This underestimate is in part possibly due to the effects of rotation during cooling. Their unique motional remanent magnetization is quite fascinating, but may be detrimental to the spherules' ability to retain a strong enough NRM, preventing them from displaying evidence of an impact-generated paleofield at Lonar Crater. / by Shelsea A. Pedersen. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996. / Includes bibliographical references (leaves 57-60). / by Brian Scott Racine. / M.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references. / With homogeneous bedrock, dramatic rainfall gradients, and remnant surfaces that constrain their age, initial topography, and vertical motions relative to sea level, volcanic ocean islands provide an exceptional natural experiment in landscape evolution. Analyses traversing gradients in island climate and bedrock age have the potential to advance our understanding of landscape evolution in a diverse range of continental settings. Yet, islands are initially conic, net subsiding, boundary-dominated, and initially permeable landmasses, in many ways dissimilar to most continental landscapes. This thesis examines unique aspects of island landscape evolution, and it exploits steep climate gradients and variations in bedrock age on volcanic ocean islands to understand controls on rates and patterns of erosion and the contribution of lithosphere and mantle processes to surface deformation at hotspots. Through physically-based modeling, analysis of remote sensing and geochronologic data, and field measurements, this thesis examines (1) the dominant mechanisms of vertical motion in the Hawaiian Islands, (2) the influence of wave power on cliff retreat rates in the Hawaiian Island over geologic timescales, (3) the control of rainfall rates on the efficiency of bedrock river incision on the Hawaiian Island of Kaua'i, (4) the evolution of erosion rates over the course of landscape development on Kaua'i and other volcanic ocean islands, and (5) the mechanisms that cause volcanic ocean islands to ultimately subside below sea level to form atolls and guyots. These analyses provide empirical evidence for climatic control on erosion processes and they constrain the dynamics of plume-plate interactions at oceanic hotspots. / by Kimberly Lynn Huppert. / Ph. D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 34-35). / The formation of the volcano Olympus Mons, is linked directly to the geodynamic history of both Tharsis, and Mars as a whole. We sought to constrain the bulk formation period using paleo-topographic evidence. On the northeastern edge of the flexural trough, we located a lava flow whose path is radically discordant with current down-slope directions, indicating entrenchment prior to large-scale flexural trough formation. To constrain the end of bulk formation, we used the aureole deposits that surround the flanks of Olympus Mons, and were a consequence of crustal fracture under the weight of Olympus. Applying crater retention age dating to images from THEMIS VIS and THEMIS IR, we proposed the bulk formation of Olympus Mons occurred between 3.67 -010+005 Ga and 3.53-0.28+0 09 Ga. / by Lauren M. Jozwiak. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997. / Includes bibliographical references (leaves 58-60). / by Vladimir I. Osychny. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1986. / Microfiche copy available in Archives and Science / Vita. / Bibliography: leaves 87-93. / by Kevin G. Speer. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1998. / Includes bibliographical references (p. 40-41). / by David Michael Sirkin. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008. / Includes bibliographical references (p. 167-174). / This thesis examines the mechanisms responsible for the abrupt onset of monsoon circulations, focusing on the role played by wind-evaporation feedback and its interaction with angular momentum conserving flow. The first half of the thesis examines the effect of wind induced surface heat exchange (WISHE) on nonlinear, axisymmetric Hadley circulations in a convective quasi-equilibrium framework. For thermal forcings localized off the equator, WISHE is found to reduce the critical forcing amplitude needed to produce angular momentum conserving flow. For forcings that are subcritical even with the effects of WISHE, the combination of WISHE and momentum advection is shown to nonlinearly enhance the circulation strength for all but the weakest forcings. These results hold for the time-dependent response to seasonally varying forcings: for forcings of intermediate strength, WISHE produces an abrupt onset of solsticial flow when only a linear response would otherwise occur, while for strong forcings WISHE shifts the abrupt onset to an earlier time in the seasonal cycle. The second half of the thesis examines the consistency of these idealized results with the onset of the South Asian monsoon in both observations and a detailed three-dimensional model. Observational composites of monsoon onset are consistent with a wind-evaporation feedback in that the increase in baroclinic flow during onset is accompanied by a large increase in surface enthalpy flux over the off-equatorial ocean. This increase in surface enthalpy flux is collocated with the peak increase in deep tropospheric ascent. Results from the three-dimensional numerical model were less conclusive in that this model did not successfully simulate an abrupt monsoon onset even with WISHE, although WISHE did strongly control the intensity and spatial structure of the model's mean summer circulation. / (cont) In particular, a version of the model integrated without WISHE failed to produce a strong, angular momentum conserving monsoon circulation. Combined with the axisymmetric model results from the first half of the thesis, this suggests that the thermal forcing of the South Asian land mass may not be sufficiently strong in the absence of WISHE to produce angular momentum conserving monsoon flow. / by William Ronald Boos. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997. / Includes bibliographical references (leaves 233-244). / by Gunter Siddiqi. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995. / Includes bibliographical references (p. 248-253). / by Mototaka Nakamura. / Sc.D.