Abstract: Global water resources have been under severe stress due to various factors including poor management, pollution and changes in rainfall patterns due to climate variability. The small islands of the Caribbean, such as Jamaica, have not been spared; prolonged periods of drought, extreme weather events and increased urbanization have led to water shortages and impaired water quality.
Sustainable management of these natural water resources requires an understanding of the dynamics of their physical behavior and their chemical constituents. Environmental tracers have proven to be very effective tools for studying the transport and mixing of surface and subsurface water on regional and global scales.
This lecture will introduce the audience to the use of stable and radioactive isotopes as tracers in the investigation of the fresh and coastal waters of Jamaica. The talk will describe the analytical techniques used in these isotopic studies, present findings related to the sources, pathways and fate of nutrients and other inorganic contaminants, and suggest implications of these findings for the sustainable management of Jamaica’s water resources.

University of California, Santa Barbara

University New South Wales

Abstract:  Rockfalls are a defining feature of the cliffs of Yosemite National Park, with a rockfall occurring every five days on average.  Yosemite is an ideal natural laboratory to study rockfall processes, but it comes at a cost: rockfalls pose considerable hazard to the park’s 4-5 million annual visitors.  Combining traditional field mapping with remote sensing tools such as lidar, structure-from-motion photogrammetry and thermal imaging, this talk will summarize the findings from more than a decade of collaborative rockfall research, ranging from how rockfalls control long-term landscape evolution to the challenge of ensuring visitor safety in one of the world’s most popular parks.

Abstract: Humans are vastly modifying the earth system, with identifiable impacts across the land surface, cryosphere, ocean and atmosphere. Here, we will explore two example applications of how explainable AI (XAI) techniques can help us visualize and quantify these changes over time. Both parts of this talk serve as examples of how viewing our climate through an AI lens has the power to uncover new insights into anthropogenic change – allowing scientists to ask “why?” but now with the power of machine learning.

Talk abstract and summary

Abstract: The surface of Venus is covered with some of the largest volcanoes in our Solar System, including some fresh and unweathered lava flows, based on orbital spectroscopic and radar measurements. However, rocks on Venus are in contact with its hot (~470° C) and caustic (CO₂ with S) atmosphere, which should alter these rocks and produce coatings of iron-oxides and sulfates on the rocks surface. These coatings should be observable from orbital measurements. Therefore, unweathered lava flows are thought to be geologically very young. Future missions VERITAS, DAVINCI, and EnVision will fly in the next decade and will image these volcanoes. However, to constrain the age of these unweathered lava flows from current and future data sets, the rate of alteration and how alteration minerals affect orbital measurements are needed. Here I will discuss what is known about igneous petrology of Venusian lava flows and specifically focus on recent alteration experiments that suggest unweathered lava flows are only a few years or up to a decade old.

Abstract: Alluvial fans may represent one of the last widespread signs of significant fluvial activity on Mars’ surface. Understanding the climatic conditions during the formation of these features may provide key insights on habitability and climate change on Mars.

Numerous studies have used data and theory from terrestrial fans from warm, arid, rainfall-dominated climates to estimate flow discharges, runoff rates, and total water volumes that likely built Martian fans. However, it has been suggested that Martian fans sourced water only from snowmelt, and perhaps under periglacial conditions. Thus, there is a knowledge gap about the dominant processes building fans under periglacial conditions, and importantly for Mars, a lack of understanding about the characteristic flow magnitudes during depositional events.

In this talk I will present results from a field-based terrestrial analog study involving characterization of the sedimentology and geomorphology of a periglacial alluvial fan in the Richardson Mountains, Northwest Territories, Canada. I will (1) qualitatively describe the range of sedimentary processes occurring on a periglacial alluvial fan and compare them to prior observations, (2) report measured flow discharges and runoff rates that occurred during a summer storm event, and (3) show that melt rates suggested for Mars are capable of entraining and transporting appreciable amounts of sediment by fluvial processes.

Multiple new policies have been developed to improve water quality in our lakes and streams; however, water quality remains a persistent problem. In this talk, Nandita Basu will address the nature of water quality challenges, especially focusing on long term legacies of nutrients, and discuss opportunities for addressing some of these challenges through a combination of top-down analysis — using large geospatial datasets to identify watershed functional  traits — and mechanistic modeling, from the reach to the watershed scale. Through this discussion, she will highlight novel approaches for regional- and global-scale solutions to water quality challenges.

In this presentation, I start with large-scale observation of seismicity migration and stress/fault distributions. Multi-scale analysis of seismicity migration allows us to derive hydraulic properties for the Arbuckle group and the crystalline basement. These parameters contributed to large-scale modeling that suggested the importance of poroelastic stress from fluid injection. With detailed analysis of the stress state of seismogenic faults, we find that fault stress state could strongly influence temporal evolution of earthquake sequences. Then, I discuss diverse triggering processes observed during several individual sequences. The Woodward sequence in western Oklahoma suggests that earthquake-to-earthquake triggering drives the fault activation. The Guthrie sequence in central Oklahoma occurred within a complex fault mesh network, and showed evidence of aseismic slip along a normal fault. These detailed observations provide a reference framework for future earthquake rupture simulations within different fault systems, and insights into the triggering processes during fluid-driven natural earthquake sequences.

Abstract: The Last interglacial (~125ka) was 0.5-1.5 ºC warmer than today, making it an interesting natural experiment for how ice sheets respond to modest warming. In this talk I will first describe past estimates for Last interglacial sea level and corresponding polar ice retreat before presenting our new assessment from sea level data in the Bahamas. I will show our field evidence and describe how we can leverage the spatial extent of the data to constrain the contribution of glacial isostatic adjustment to past sea level. Based on these data, we find that Last Interglacial sea level very unlikely exceeded ~5m, which is below the current estimate from the IPCC. Next, I will present new Last Interglacial sea level data from northwest Europe, and argue that these observations predominantly constrain the contribution from the Antarctic ice sheet during the Last interglacial. Combining both results (from the Bahamas and northwest Europe) allows us to not only produce a new time-varying estimate of Last Interglacial sea level, but also partition this melt between Greenland and the Antarctic ice sheet. I will end by speculating what these new results mean for future sea level rise.

Abstract: This presentation will highlight three examples of rheological heterogeneity recorded in exhumed exposures of deep continental crust. The first two are examples where lithological contrasts influenced the rheological behavior of kilometer-scale ductile shear zones, and the third is an example of mechanical heterogeneity in the form of initial fractures that evolved to ductile shear zones. While the examples vary widely in scale and tectonic setting, a common observation is that heterogeneity (lithological and mechanical) and fluid availability (and fluid-rock interaction) played critical roles in promoting active deformation mechanisms and transient ductile and brittle behavior.
The Paleoproterozoic Hell Roaring Creek shear zone is a 3 km wide, steeply dipping amphibolite-facies structure exposed in the northern Madison Range of southwest Montana (~25 km paleodepths). Mineral assemblages and local evidence for metasomatism suggest deformation developed under relatively wet conditions. Stretching lineations within the shear zone have a bimodal geometry, with nearly down-dip orientations in most lithologies but shallowly plunging orientations in the most quartz-rich lithologies. Dextral shear sense indicators are consistently observed on subhorizontal surfaces. Observations within and adjacent to the shear zone suggest that the steep fabric elements are at least partly inherited from an earlier episode of deformation and were enhanced during subsequent shear zone activity. Thus, the shear zone exhibits strain partitioning during transpression due to rheological contrast among lithologies and heterogeneity from inherited structures.
PseudotachylyteThe Paleoproterozoic Cora Lake shear zone in the western Churchill Province of the Canadian Shield is a several km wide zone of granulite- to upper amphibolite-facies mylonite which hosts synkinematic pseudotachylyte (~30-25 km paleodepths). Limited evidence for hydrous fluids suggest relatively dry conditions. The shear zone is localized at a major lithological and terrane boundary, with the pseudotachylyte network centered on the more intensely deformed, finer-grained ultramylonitic core. We conclude that episodic brittle failure during lower-crustal ductile shear was most likely due to local stress amplification from a relatively common type of km-scale lithological heterogeneity.
Fracture systems in otherwise homogeneous granites in the Alps and in meta-gabbronorite dikes in Montana systematically evolved into outcrop-scale ductile shear zones under amphibolite- to eclogite-facies conditions, with strong influences from locally fluxing aqueous fluids. The interpreted shear zone evolution involved (1) initial strain localization by nucleation on pre-existing, or in some cases nearly co-eval, fractures that focused fluid infiltration, (2) grain-size reduction by microfracturing, dislocation creep, and synkinematic metamorphic reactions driven by chemical potential gradients, and (3) a switch to grain-size sensitive granular flow accommodated by fluid-assisted diffusion in ultramylonite.

Abstract: Human uses of land have transformed and fragmented ecosystems, degraded biodiversity, disrupted carbon and nitrogen cycles and added prodigious quantities of greenhouse gases (GHGs) to the atmosphere. However, in contrast to fossil-fuel carbon dioxide (CO2) emissions, trends and drivers of GHG emissions from land use (including both land-use change and agriculture) have not been as comprehensively and systematically assessed. I’ll present recent work my group has done to analyze country-, process-, GHG- and product-specific inventories of global land-use emissions over the last half-century, including uncertainties and decomposition of key demographic, economic, and technical drivers. I’ll then present results of a related analysis of the land-use emissions embodied in international trade and discuss implications for mitigation efforts. Finally, I’ll briefly introduce the Carbon Monitor, an international collaboration hatched during the pandemic to estimate global, country, and U.S. state-level fossil emissions in near real time.