Colloquium Schedule

Faculty Lightning Talks, UMD Geology

September 1, 2023 at 11:00 am (SYM 0200)

Michael BrownProduction of continental crust and the pulse of the galaxy
Megan NewcombeEfficient degassing of early-formed planetesimals restricted water delivery to Earth
Jay KaufmanThe emergence and environmental consequences of Cryogenian sponge-grade animals in south Australia
Ricardo ArevaloThe (dis)advantages of a good acronym
Mengqiang "Mike" ZhuOccurrence of manganese oxides in Martian soils: Implications for paleoenvironment of Mars

Stanley Grant, Virginia Tech

Transit times link sodium sources to drinking water quality in a One Water system

September 15, 2023 at 11:00 am (SYM 0200)

The One Water approach to water resources management aims to improve water equity, affordability, and access through the comprehensive co-management of all local water resources. The success of this approach hinges on quickly addressing emerging water supply and water quality threats, even in cases where top-down regulatory remedies are not available. In this study we focus on an increasingly common water quality challenge in One Water systems, salt management, using the Occoquan Reservoir in Northern Virginia as a testbed. This reservoir is one of the first and largest indirect potable reuse systems in the United States. It has been successfully operated for the past 50 years under a regulatory framework called the Occoquan Policy. However, rising levels of sodium ions (an unregulated contaminant) has exposed a potential gap in the governance of this system. We demonstrate that unsteady transit time theory can help set the stage for stakeholder-driven bottom-up management of sodium pollution, by improving the predictability of system dynamics (``if a particular source is reduced, what is the likely impact on sodium ion concentrations in the reservoir?"), enhancing knowledge of the social-ecological system (``how do system-level processes and feedbacks influence options and outcomes?"), and supporting the development of collective action rules (``who should be engaged, what rules should they follow, and why should they participate?"). Our analysis also highlights the environmental and societal implications of both action and inaction on this emerging issue.

Emmanuel Codillo, Carnegie Science EPL

The ascent of mélanges: geochemical and experimental constraints

September 22, 2023 at 11:00 am (SYM 0200)

Subduction zones are the major sites of recycling of rocks and water into the Earth’s interior. These subducted materials impart their geochemical signatures to the overlying mantle which are ultimately reflected in the compositions of arc magmas worldwide. However, the physical and chemical processes that lead to the transport of key elements and volatile components from the slab to the overlying mantle remain debated. Recent studies on high-pressure mélange rocks have emphasized their roles in slab-to-mantle transfer mechanism and arc magma formation. Mélange rocks are mixtures of sediments, oceanic crust, ultramafic rocks, metasomatic rocks, and fluids formed along the slab-mantle interface. They display a range of elemental and isotopic signatures reflecting distinct input lithologies and fluids but have phase equilibria different from any subducted oceanic basalt and sediment inputs. It has been suggested that mélange rocks may be able to buoyantly ascend from the slab-top into the overlying mantle and transfer their compositional signatures to the source regions of arc magmas. In this talk, I will present geochemical data from global arcs and present new interpretations on the evolution of slab-to-mantle transfer mechanisms from subduction initiation to maturity. To evaluate mélange melting and its likelihood for diapirism, I will present new experimental data on the phase equilibria, solidus temperatures, and densities of natural mélange rocks over a range of pressure-temperature conditions. Finally, I will discuss how mélange melting and diapirism can influence the interpretations of both geophysical signals and geochemical characteristics of magmas in subduction zones.

Itay Halevy, Weizmann Institute of Science

Rusty records of climate regulation and a spectacular exception

September 29, 2023 at 11:00 am (SYM 0200)

The Sun has gotten 25% brighter since it formed. Concurrent with this solar brightening, there is evidence for dramatic changes in the composition of Earth’s atmospheric greenhouse. The climatic response to these changes must underpin our understanding of Earth’s physical climate system. However, there has been vigorous debate about the climatic response, as constrained by the oxygen isotopic composition (δ18O) of marine sedimentary rocks. This ~4-billion-year isotopic record has yielded two contrasting end-member interpretations. In one, δ18O of seawater has remained approximately constant, and the temperature of Earth’s surface has decreased from an early 70-80°C to the present global average of ~15°C. In the other, the global average temperature has been approximately constant and δ18O of seawater has increased by 10-15 permil. These two end-member scenarios have profoundly different implications for Earth’s climate through geologic time, the mechanisms that regulate it, and the effects on a wide range of Earth-system properties. To address this gap, we developed the δ18O of marine iron oxides, which strongly suggests an increase in seawater δ18O over Earth history rather than high early temperatures. Using this new record and existing isotopic data, we show that Earth’s temperature has largely been regulated at a global average of ~10-20°C, with implications for long-timescale climate-stabilizing feedbacks. In a spectacular exception to this rule of climate regulation, some of our samples come from a ~50-million-year-long global glaciation, the Sturtian “snowball Earth”. We use these samples to reveal that during this interval a staggering 15-30% of Earth’s water was locked in ice. Despite the frozen surface conditions, our results also suggest that at least half of the ice came from snowfall in an active hydrological cycle.

Kate Tully, UMD Plant Sciences

Salty waters unlock soil secrets: the biogeochemistry of saltwater intrusion on coastal farmlands

October 13, 2023 at 11:00 am (JMP 3201)

Saltwater intrusion is the landward movement of sea salts. It can occur in advance of sea level rise and is often invisible especially in the low-lying Mid-Atlantic region. Saltwater intrusion can lead to the migration of marshes and the formation of ghost forests. It can also lead to the invasion of nonnative species and the crop failure. This talk will discuss the effects and extent of saltwater intrusion in Maryland, Delaware, and Virginia. We will focus on the movement of carbon, phosphorus, and nitrogen among water, soils, and plants and discuss potential future management strategies for agricultural land.

Hannes Bernhardt, UMD Department of Geology

From the Red Planet's biggest hole to its largest caldera and beyond - Piecing together the geologic histories of Hellas Planitia and Malea Planum on Mars

October 20, 2023 at 11:00 am (JMP 3201)

1,700 km wide Hellas Planitia is the floor of the second largest, topographically well-defined impact basin in the Solar System and the largest physiographic feature in the red planet's southern hemisphere. As a major depositional sink, it hosts a multitude of materials of various origins, reflecting eolian, glacial, fluvial, volcanic, impact, and potentially lacustrine processes of the past 4 billion years. The infill of the Hellas basin therefore is a kilometers-thick stack of pages from the book of martian geologic history, which I assessed by producing a detailed geologic map and several in-depth analyses of significant and unique landforms. To further improve the deciphering of this book, the project was followed by investigating one major source region for the Hellas infill materials: an area just south of the basin called Malea Planum, which is the oldest of the large volcanic provinces on Mars and contains what might be the red planet's largest and oldest volcanic caldera, testament to enormous ash eruptions. Likewise a comprehensive map and detailed morphologic analyses of Malea Panum revealed a history that could then be compared with that of Hellas, thereby identifying how these regions interacted through time and what the potential effects on the climate evolution of Mars were. After a short general introduction on Mars climate history and planetary geologic mapping, some of the most significant landforms of Hellas Planitia and Malea Planum will be briefly discussed and an overview of their histories within the larger framework of martian evolution will be given.

James Farquhar, UMD Department of Geology

The prospects of atmospheric methane isotopologues for fingerprinting sources on global to local scales

October 27, 2023 at 11:00 am (JMP 3201)

Laura Lapham, University of Maryland Center for Environmental Science

Investigating methane flux from permafrost settings and deep-sea methane seeps

November 3, 2023 at 11:00 am (JMP 3201)

John Bargar, Pacific Northwest National Laboratory

A Molecular Observation Network (MONet) database for modeling Soil Function at regional scale

November 17, 2023 at 11:00 am (JMP 3201)

While carbon and essential nutrients are the currency of healthy ecosystems, we have poor mechanistic understandings of their chemical processing pathways through soils and natural waters, and of how these molecular processes aggregate across regions. We have a similarly poor understanding of emissions processes and subsequent chemical behavior of reactive organic volatiles and aerosol particles at terrestrial-atmospheric interfaces. The existing state of knowledge does not adequately support model development in these areas from molecular to Earth Systems scales. Big data are needed across this continuum to enable next generation modeling and experiments. To provide regional scale molecular data, the EMSL Molecular Observation Network (MONet) has launched a new open science user program to interrogating molecular-level information on the composition and microstructure of soil, water, air, and resident microbial communities across the continental US. The Environmental Molecular Science Laboratory (EMSL) is a national user facility supported by the U.S. Department of Energy, Office of Science. EMSL users, partners, and citizen scientists from around the US will have access to high-throughput analysis workflows that will produce high-resolution data on carbon molecular composition, soil pore network structure, hydraulic properties, microbial metagenomes, organic volatiles, and aerosols. The Joint Genome Institute (JGI) and National Ecological Observatory Network (NEON) are crucial partners. High-resolution molecular and pore structural data will complement soil measurements performed by existing networks such as NEON and Ameriflux. Data will be stored in a cutting-edge FAIR database that will be accessible with tools designed to facilitate data interrogation, modeling applications, and next-gen experiment planning.   

The coordinator for the Colloquium Series is Dr. Mengqiang "Mike" Zhu. You can contact him at mqzhu [at] umd [dot] edu.

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