Earth’s Moon, when viewed from Earth, always shows the same face. The compositional, topographic, and structural asymmetry between the Moon’s nearside and farside hemispheres has …
The lithosphere-asthenosphere boundary is the world’s most ubiquitous plate boundary system, separating the high viscosity lithosphere from the underlying convecting mantle asthenosphere. Thoroughly characterizing the …
Volcanic hazards monitoring relies heavily on constraints offered by geophysical inversions to decipher the structure of subvolcanic magmatic systems. Over the past decades a multidisciplinary …
This dissertation explores the recent history of non-polar ice-rich paleodeposits on Mars, primarily through the analysis of pedestal craters. Pedestal craters are defined by having …
Volatile elements (C, H, F, S, and Cl) have a profound impact on the evolution and differentiation of planetary bodies and their atmospheres. Therefore, constraining …
This thesis details advances in experimental deformation methods applied to investigate the creep behavior of antigorite serpentinite. Antigorite is present in downgoing slabs and nearby …
The system of plate tectonics governs the transport of material between Earth’s interior, hydrosphere, and atmosphere to create a dynamic planetary surface that sustains life. …
Thermal infrared spectroscopic measurements record not only compositional information about the properties of a target but also information about the environmental conditions in which the …
Recent development of biomarker-based paleoclimate proxies provides new analytical capabilities through which paleoenvironmental change can be inferred. Here, I explore the utility of these organic …
“Pink” Mg-spinel is a rare mineral among rock samples returned during the Apollo missions and is typically associated with the lunar highlands Mg-suite (a small …
The Great Barrier Reef, the world’s largest coral reef ecosystem, is subjected to a number of global and local stressors, including tropical cyclones. Although tropical …
The agricultural frontier of the Brazilian Amazon is one of the fastest growing agricultural regions in the world, and rapid deforestation makes it one of …
The lithosphere, the plate in ‘plate tectonics’, preserves a record of past and present tectonic processes in its internal structures and its boundary with the …
Continental climate experiences significant changes and severely affects human's life. Quantitative reconstruction of past continental climate changes is extremely important for understanding their mechanisms in …
The nature of the early martian climate remains unsolved. Geologic evidence, including valley networks, paleolakes, and groundwater release, suggest that the long-lived (Noachian-spanning) early climate …
Diverse hydrous minerals have been identified on Mars and suggest a rich history of water-rock interactions in a variety of aqueous environments. Fe/Mg clays and …
In the coming decades to centuries drastic changes in temperature and precipitation patterns pose new challenges for societies and ecosystems in the North Atlantic region. …
In the coming decades to centuries drastic changes in temperature and precipitation patterns pose new challenges for societies and ecosystems in the North Atlantic region. …
Continued development of organic geochemical proxies for paleoclimate reconstructions are proving invaluable for understanding climate dynamics and climate-ecosystem interactions. Here I investigate the utility of …
Thermal evolution of the planet interior is a fundamental problem in Earth and planetary sciences. Geothermobarometers and geospeedometers are powerful tools in studying the thermal …
The history of Mars’ paleoclimate is explored using sedimentary records from both the Noachian and Amazonian periods. Sedimentary structures indicative of a progradational delta are …
Under the current paradigm of Mars history, the planet is thought to have undergone a global climatic change, from relatively warm and wet conditions during …
Dynamic friction during earthquakes, sliding at seismic slip velocities, is interpreted to be low (<0.1). Thermal pressurization of pore fluids (or simply TP) is widely expected to be activated and dominant during earthquakes, though due to the intricate boundary conditions of TP it is rarely observed and studied in controlled laboratory conditions. This thesis explores the controls and limitations of TP through laboratory experiments and theoretical calculations. TP is activated in velocity-step experiments on water-saturated, low-permeability (<10-19 m^2) Frederik diabase saw-cut faults. The diabase samples are thermally-cracked and their permeability is measured before the friction experiments. Dynamic frictional weakening is short-lived in bare surface faults but is more persistent in wider, gouge-filled faults. Friction decreases by up to 52% of its initial value at relatively modest fault slip velocities of 2.5 mm/s, which suggest that TP may be activated in the early stages of fault slip in natural fault zones. Friction transitions during these experiments from weakening to strengthening and over successive TP events, implying that the hydraulic diffusivity of the fault rocks increase during TP. Stress calculations and measurements show that tensile stresses are induced during TP in the experimental faults, which promote microcrack dilation, which correlates with an increase in hydraulic diffusivity. Theoretical calculations demonstrate that key parameters that control TP evolve considerably during TP, as temperatures and effective stress change in the fault zone. Specifically, the pressurization factor, which controls fluid pressurization, is highly sensitive to temperature, where at high temperatures (>350℃) it decreases continuously due to an increase in fluid …</0.1).>
Detecting minerals and determining their compositions is fundamental for reconstructing thermal and chemical evolution of the lunar crust. Estimating Mg-Fe composition of mafic minerals and …
Climate variability in the Indian Ocean region affects the livelihoods of billions of people. Paleoclimate reconstructions can provide critical insights into the fundamental oceanic-atmospheric processes …
Serpentine is a common mineral in many seismically active regions of the crust and mantle. In this dissertation, rock deformation experiments were conducted on serpentine …
Alkenones are lipids produced by certain haptophyte algae and are excellent sensors of temperature change. This dissertation investigates the stable isotopic and organic geochemical aspects …
Today, more than any preceding time, understanding the response of terrestrial ecosystems to changes in climate is imperative due to the extremes to which we, …
Geological materials in nature and in the lab are often subjected to intense driving forces created by large gradients in thermodynamic potentials. Under such conditions, …
This thesis investigates the diversity and ecology of alkenone-producing haptophyte algae. Focusing on lake-dwelling haptophytes, this thesis describes the paleoclimate implications of haptophyte diversity. Additionally, …
This body of research uses numerical models to investigate the dynamics of melt generation in the asthenosphere, accumulation at the base of the lithosphere by …
While unstable on present-day Mars, liquid water was an important geologic agent in Mars' past. This work investigates the nature and timing of aqueous processes …
The nature of the early Mars climate is currently debated. Geologic evidence from valley networks and crater basin paleolakes suggests that early Mars (the Noachian …
The ejection of mass during an impact event is a shock-driven process that shapes the distribution of materials on planetary surfaces. Ejection velocities dictate the …
Impact cratering is a ubiquitous process affecting planetary surfaces in the solar system. The most probable impact angle is 45°, and ¼ of all impacts …
Because of the different characteristics of seismic velocity and density sensitivity kernels for Rayleigh wave amplification and phase velocity, combining observations of surface-wave amplification with …
The goal of this work was to provide a foundation for quantitative assessment of H2O abundance of terrestrial and extraterrestrial geologic materials using visible-near infrared …
Past hydroclimatic change is shown from the reconstruction of paleo-lake levels from New Long and Rocky Ponds in southeastern Massachusetts, and Davis Pond in western …
Abstract of Experimental and Field Constraints on the Physicochemical Evolution of the Lunar and Terrestrial Mantles, by Nicholas Dygert, PhD., Brown University, May 2015. This …
The first three chapters of this thesis are focused on experimental determinations of noble gas solubility in a variety of materials relevant to partial melting …
This thesis studies the shergottite family of martian meteorites using a variety of experiments performed on natural and synthetic samples. The study determines the crystallization …
This PhD thesis presents a comprehensive exploration of Earth’s upper mantle from global and regional perspectives, with a particular emphasis on the stable cores of …
The nature of the early martian climate, hydrological cycle, and their relationship to the impact cratering process has remained enigmatic, but are critically important in …
Geodynamic models are developed to understand the geologic evolution of icy satellites and Kuiper belt objects. The key scientific questions addressed by this thesis are: …
The Songliao Basin in Northeast China contains one of the most complete terrestrial sedimentary records of the Cretaceous and represents an important terrestrial paleoclimate archive. …
In Providence, Rhode Island, communities of color and neighborhoods with high asthma rates are not well-represented by the coarse spatial resolution of current government-operated monitoring. …
Recent climate extremes, including floods, droughts, and hurricanes, have had devastating effects worldwide, driving new research aimed at developing better prediction of such events. Understanding …
Tropical dry forests are an extensive biome that supports biodiversity, food, water and energy resources for millions of people. Among global tropical dry forests, the …
Recent data from orbital spectrometers at the Moon have, for the first time, directly identified the mineral structure of plagioclase feldspar on the lunar surface. …
The availability of nutrients in surface waters, including inorganic nitrogen (N) (i.e., nitrate (NO3-), nitrite (NO2-), and ammonium (NH4+)), regulates estuarine and ocean primary production. …
The climatic history of Mars has been indirectly studied through the remote detection of minerals produced by chemical alteration across its surface. While the martian …
In this dissertation, I present a large geochemical data set of submarine glass, melt inclusions and whole rock collected from across the Galapagos Archipelago to …
The modern surfaces of planetary bodies throughout the solar system are shaped by their ancient thermal and interior evolution. Here we work to understand the …
Understanding the characteristics and drivers of climate variations is imperative to advancing our knowledge about the evolution and changes of the Earth system. The Holocene …
Stress-reduction, creep, grain-growth, and attenuation experiments were conducted on polycrystalline water ice to examine the links amongst microstructural steady-state, the mechanical response to transient loading, …
Heat has been, and will continue to be, a major environmental hazard, public health concern, and local and national economic and security challenge. Extreme high …
Dynamical shifts in the behavior of the Eastern Equatorial Pacific Ocean (EEP) likely amplify changes to the global climate system through their control on heat, …
Orbital and landed investigations of Mars have revealed a variety of secondary minerals on the surface consistent with past surface or subsurface liquid water and …
The Pliocene (5.33-2.58 million years before present (Ma)) is the most recent epoch of Earth’s history when atmospheric pCO2 levels were as high as the …
The Peru margin plays a significant role in global climate dynamics and biogeochemical cycling. Situated between 4-15°S off the western coast of South America the …
The next few decades are expected to host a reinvigoration of planetary exploration by humans. The most likely targets for near-term human exploration include the …
Tropical African mountains are particularly sensitive to current and future climate change. Reconstructions of past variations in temperature and precipitation in tropical Africa are useful …
Valley networks, many connecting voluminous paleolakes, dissect the martian highlands, but ceased activity ~3.7 billion years ago. The nature of the climate that allowed so …
The life cycle of a continent is driven by the very dynamic lithosphere and asthenosphere system. The deformation associated with tectonic events, such as plate …
Upon hypervelocity impact, projectile and target materials are frequently shocked to pressures and temperatures sufficient to induce complete vaporization. Vaporization associated with impacting comets and …
Policy and practice in major river systems of the world continue to degrade ecosystems and undermine sustainable use. Freshwater resources are multi-valued, and transboundary river …
This work is perhaps the first major study integrating mineralogical and morphological properties of lunar impact melt deposits using the new generation remote sensing data. …
Detailed textural, mineralogical and chemical analyses of extraterrestrial materials have raised numerous questions about the igneous evolution and cooling histories of their parent bodies. Remote …
The thermohaline instabilities imposed by sea ice floes on the surface ocean create submesoscale eddies which are poorly modelled in modern oceanographic or atmospheric models. …
The state of the climate during the Late Noachian/Early Hesperian has been a longstanding question in Mars research. The abundant fluvial features and alteration minerals …
Reactive nitrogen gases (e.g., NOx = NO + NO2) emitted to the atmosphere eventually return to the surface environment as nitrate (NO3-) deposition, which causes …
Partial melting of the mantle occurs predominantly in the spinel lherzolite stability field, where pyroxenes are consumed to produce olivine and basaltic melt. The phase …
Over the past four decades, the Cerrado region of Brazil has transitioned from a land of sparsely inhabited forests and shrublands to an industrial agriculture …
Ocean surface gravity waves, especially the resulting Langmuir turbulence, affect the ocean surface vertical mixing, yet are missing in most of the global climate models …
The Indian Summer Monsoon (ISM) is vital to over one-fifths of the world’s population who depend upon monsoonal rains. Recently collected marine sediment cores offer …
This work presents novel Miocene – Pliocene (13 - 2.6 Ma) sea surface temperatures (SST) from the Mediterranean Sea, North Atlantic, South Atlantic and North …
Seismic anisotropy in olivine and orthopyroxene mineral crystals enables us to infer first-order flow characteristics in the asthenospheric mantle and the preserved tectonic history in …
A suite of lunar materials is examined with reflectance spectroscopy. Reflectance spectroscopy is capable of collecting compositional data for planetary surfaces at high spatial resolution …
Leaf wax D/H ratios are widely used to reconstruct environmental water D/H ratios in paleoclimatology. However, accurate quantitative assessment of precipitation D/H ratios from sedimentary …
The objective of this thesis is to use first order geochemical and geophysical observations to understand melt generation and migration processes beneath mid-ocean ridge spreading …
Inland waters (lakes, rivers, reservoirs, wetlands) are the largest natural source of the greenhouse gas methane, representing 40-50% of total emissions. Emission sources are characterized …
How temperature influences the micromechanics of faulting is central to the mechanics of earthquakes and faulting. Quantitative microscopy was conducted on a quartz sandstone experimentally …
Moist convection fundamentally influences Earth’s climate, particularly through precipitation and clouds. However, continental moist convection is poorly represented in global climate models, and the land …
Organic matter is present on many bodies in the solar system. The parent bodies of carbonaceous chondrite meteorites, for example, are known to contain a …
The northern high latitudes are currently experiencing some of the fastest rates of environmental change on Earth, including reductions in sea ice extent, melting of …
Over the coming century, global temperatures are expected to rise by 1.8°-4°C due to anthropogenic emission of greenhouse gasses. This increased radiative forcing and associated …
Knowing how the Earth system will respond to the human release of greenhouse gases (GHG) requires knowing something about how climate has responded to similar …
The nitrogen and oxygen isotopic composition of nitrate in ice cores offers unique potential for examining reactive nitrogen oxide (NOx) budgets and oxidation chemistry of …
The question of how to interpret precipitation isotope records in East Asia is an ongoing debate and has implications for understanding climate dynamics in East …
There is substantial geologic evidence, including extinct valley networks and paleolakes, for a period of increased aqueous activity on the surface of Mars prior to …