Joel Johnson, Ph.D., Associate Professor in Earth and Planetary Sciences at UT Austin

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Dr. Joel Johnson is an Associate Professor in Earth and Planetary Sciences at UT Austin, and a geomorphologist who focuses on fluvial processes.  He got his PhD from MIT in 2007, and has been at UT since 2009.  His research focuses on quantifying active surface processes and relating them to the evolution of topography over both short and long timescales. Research topics include quantifying how climate gradients and bedrock properties influence topographic development, understanding controls on tsunami and storm surge deposition, and constraining feedbacks between sediment transport rates, sediment sorting, vegetation and the evolution of bed roughness in mountain rivers.  In addition, he has taught an undergraduate course in geoethics for several years, and enjoys discussing questions of values on which reasonable people can disagree.

Rebecca Smyth, M.A., P.G., Bureau of Economic Geology, UT-Austin

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Rebecca C. “Becky” Smyth is now a part-time retiree at UT Austin BEG. She grew up in Dallas, TX and Richmond, VA, earning a B.S. in Geology from Va. Tech (Go Hokies!) in 1980. She returned to Dallas via the Big Apple to work in Core Laboratories Petrology Division, but moved back to Austin within a few years. Here she tried becoming a chemist and took graduate classes in geology while working two part-time jobs (BEG and USGS Water Resources). In 1985 she and geologist-husband moved in with military family in England then took to the road in a VW van for 1.5 years across western and eastern Europe, Scandinavia, and USSR, ending up as farm laborers in Israel for three months. Back in Austin again, Ms. Smyth went to work in groundwater consulting then earned a Master’s in Geology at UT Austin (Hook ‘Em) in 1995 (“Porosity and Permeability Controls in the Santana Ash Flow Tuff, Trans-Pecos Texas”); darling Joanna was 4-yrs old by then. Back at BEG from 1997 through 2017, she investigated lands impacted by oil and gas production (1997-2000), airborne laser mapping (lidar) (2001-2006), and geologic CO2-sequestration (2007-2017). In 2018 she returned to BEG part-time to work on the Balmorhea-area springs project, and a few other water-related studies (TCEQ, Travis County).

Abstract

Trans-Pecos Texas is dryer now than it has been since the early aughts and beyond. Fortunately, many of the springs along the north side of the Davis Mtns, between Ft. Davis and Pecos, TX are still flowing, albeit less than they were when the U.S. Geological Survey (USGS) began reporting on them in the 1930s-1940s. Since the start of BEG research in 2018, the only significant rainfall in the region was in Fall 2022. By significant rainfall I mean an amount needed to affect brief, but measurable “freshening” in the pool at Balmorhea State Park in Toyahvale, TX. An example of freshening of pool water from >2,000 milligrams per liter total dissolved solids (mg/L TDS), almost down to drinking water standard of 500 mg/L TDS, came after multiple 1-2-inch regional (~5,000 mi2) rainfall events between August and November 2022. From whence the rainfall comes that is recharging one of the five (maybe six) candidate aquifers that are thought to contribute flow to the Balmorhea-area springs is still being studied. Great work by Jack Sharp and students, and the Texas Water Development Board, among others has been helping answer the question: Can existing and future industrial scale production of groundwater take place without more seriously impacting spring flow discharge? We at BEG, and others, think more work is needed.

Rusty Branch, P.G., R.G., Vice President and Senior Geoscientist, Gehrig, Inc.

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Rusty is a geologist and geophysicist and has been a member of the Gehrig, Inc. team since 2016. He has over 16 years of experience in the field of near-surface, applied geophysics, including UAV-based studies. He has served on many local, state, and national boards and committees of professional organizations and non-profits. Some of the positions include Chair for the Texas Section of the ASCE Geo-Institute, Chair of the Texas Chapter and national board member of the Association of Environmental and Engineering Geologists (AEG), and a leadership instructor on the local, regional, and national level for the Boy Scouts of America. He has authored and co-authored peer-reviewed publications in the fields of geology, vertebrate paleontology, and botany and he is an avid birder. His three decades of professional and academic experience cover geoscience, bioscience, computer information systems, and GIS. Rusty has a B.S. in Geoscience from Tarleton State University, a M.S. Biology (Vertebrate Paleontology) from Baylor University, and a M.B.A from University of Texas at Arlington.

Abstract

What is the true power of applied, near surface geophysics? Two decades ago, this subfield was in its infancy and not extremely popular. Since then, it has gained acceptance as a viable value-add for many hydrogeology, environmental and engineering projects. During this presentation I will review a series of interesting, recent case histories that illustrate the true power of applied geophysics. We will wrap things up with a short glimpse into the future of applied geophysics.

Robert Mace, Ph.D.

Robert Mace is the Executive Director and Chief Water Policy Officer of The Meadows Center for Water and the Environment and a Professor of Practice in the Department of Geography at Texas State University. Robert has over 30 years of experience in hydrology, hydrogeology, stakeholder processes, and water policy, mostly in Texas. Robert has a B.S. in Geophysics and an M.S. in Hydrology from the New Mexico Institute of Mining and Technology and a Ph.D. in Hydrogeology from The University of Texas at Austin.

RSVP to AGS Meetings HERE

RSVP to AGS Meetings HERE

Location

BEG Library
BEG Main Building, Building 130 
UT Austin, JJ Pickle Research Center
10100 Burnet Rd., Bldg 190
Austin, Texas 78758
Bureau Directions and Maps | Bureau of Economic Geology

Timeline

Meeting Time: 6:30 - 8:10 PM
Set Up and Refreshments: 6:30 to 7:00 PM
Student Recognition and Introductions: 7:00 PM
Browsing and Discussions: 7:15 to 8:00 PM

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Madison Callan

Madison is a senior at the University of Texas at Austin double majoring in Environmental Science, Geological Sciences and Environmental Engineering. For the last year, she has been conducting research for her honors thesis in the Jackson School Undergraduate Honors Research Program under the supervision of Dr. Toti Larson at the Bureau of Economic Geology. Her research focuses on how hydrogen gas is consumed by microbes during storage in porous reservoirs. After graduation in May, Madison plans to attend the University of California, Berkeley for a Masters in Geosystems Engineering.  

Abstract:

Renewable hydrogen energy is made possible through the storage of large quantities of hydrogen gas in salt caves and potentially in porous subsurface media. Hydrogen is injected into subsurface reservoirs where it displaces existing fluids, typically brine, oil, or natural gas, and spreads under an impermeable caprock to prevent leakage. Due to hydrogen being such a novel energy resource, there are several concerns and possible limitations associated with large-scale storage. Hydrogen is unstable as a liquid, so it must be stored as a gas; however, natural porous media such as aquifers, salt caverns, and oil or gas reservoirs host diverse microbial communities as deep as several kilometers into the subsurface. While previous studies have been conducted on the future of hydrogen energy, few analyses have been done on the behavior of hydrogen gas in the subsurface, and even fewer investigate the interaction between hydrogen and microbes. This research project focuses on examining the microbial consumption of hydrogen gas in a system able to store excess energy in a porous reservoir (HSPR). Ultimately, this work aims to monitor hydrogen consumption over time and determine the driving biogeochemical reaction pathways that occur in the presence of microbes. 

By monitoring hydrogen consumption using Wilcox core, it was concluded that iron-reducing bacteria are the most prevalent microorganism in the system, which produce ferrous iron while depleting hydrogen. The iron-stained sandstone resulted in more hydrogen being consumed than quartz sandstone; however, hydrogen consumption occurs at relatively slow rates on the scale of 105 nM/hr. Abiotic samples proved that in the absence of microbes, little to no hydrogen is lost in comparison to biotic samples. These novel data will contribute to quantifying the difference in hydrogen depletion between quartz sandstone and iron sandstone reservoirs as well as provide a deeper understanding of the reactivity of hydrogen gas in fluids containing abundant microbial communities. 

James Sun

James is a 4th year undergraduate student studying geology at the University of Texas at Austin. James has enjoyed working as an undergraduate research assistant over the past couple of years on various projects. For his honors thesis, James is working under Dr. James Gardner (Supervisor) and Wade Aubin (Graduate Supervisor) studying the kinetics of heterogeneous bubble nucleations. After graduation, James plans to attend Colorado School of Mines to pursue studies in economic geology. 

Abstract:  

The exsolution of dissolved gasses from magmas drives volcanic eruptions. These gasses exsolve by forming gas bubbles in response to decreasing magmatic pressure. Bubbles nucleate from silicate melt either homogeneously or on preexisting surfaces, such as crystals. Heterogenous nucleation is considered favorable because it has a much lower energy barrier than homogenous nucleation, and natural magmas are rarely free of crystals. Despite the importance of heterogeneous nucleation, little is known about how it varies with differing numbers and sizes of crystals in silicic melts. We are conducting an experimental campaign designed to constrain the factors that influence heterogeneous nucleation of bubbles in silicic magmas. We are conducting temperature, pressure, and time-controlled experiments using samples prepared with known numbers and sizes of crystals. Samples with different number densities of crystals of a given size will enable us to determine how bubble number densities relate to crystal abundances. 

Samples with varying sizes of crystals will allow us to recognize how nucleation sites (crystal faces, tips, corners) become important with changing decompression conditions. Samples with known crystal concentrations but different melt compositions (rhyolite-trachyte-phonolite) will enable us to discern whether heterogeneous nucleation behavior differs across the spectrum of silicic magma types. When combined with our understanding of homogeneous nucleation, this study will help to construct a more complete model for bubble formation that will elucidate the interplay between heterogenous and homogenous nucleation in erupting silicic magmas. 

David Keith 

David is a senior in the Jackson School of Geosciences Undergraduate Honors Research Program double majoring in Geosystems Engineering and Hydrogeology and Environmental Science, Geology. David was born in Austin and grew up a lifelong Longhorn but spent most of 

his life living in Boerne, outside San Antonio. David is working with Professor M. Bayani Cardenas within the Jackson School and their research focuses on measuring the thermochemical properties of Lake Travis and assessing the impact that recent drought and climate change may have had on the behavior and magnitude of lake stratification typically experienced there. David has recently accepted a full-time position within Occidental Petroleum’s Engineering Development Program as a Production Engineer and looks forward to working on projects modernizing the energy industry. Outside of work and education, David is a passionate outdoorsman, reader, and cinephile and is going to particularly enjoy watching Texas beat A&M in the SEC next year.  

Abstract:  

Lake stratification is an important process affecting the biogeochemical characteristics of inland lakes throughout the year. Lakes play a critical role in supporting inland life across the globe, providing a source of food, drinking water, biodiversity, and shelter to untold organisms and supporting millions of distinct ecosystems across the Earth. Consequently, understanding the stratification patterns of inland lakes is pivotal to understanding the health of nearby ecosystems and communities. Lake Travis, located outside Austin, Texas, is one of seven freshwater reservoirs in Central Texas collectively known as the Highland Lakes and is the sole source of drinking water for the city of Austin. In the face of anthropogenic climate change and worsening drought, a clear understanding of Lake Travis’ seasonal stratification pattern and its reaction to climatic change is needed to protect and preserve the surrounding communities. Vertical profiling of Lake Travis’ temperature, pH, dissolved oxygen, dissolved carbon dioxide, and specific conductivity, and turbidity—achieved via regular scuba dives over a 12-month period from October 2020 to October 2021—revealed that Lake Travis is a monomictic lake, meaning that it experiences a complete turnover only once a year. During stratification, a lake separates into an upper and lower layer, known as the epilimnion and hypolimnion, respectively. Thermal stratification of Lake Travis appears to occur during summer months, from April to November, while a separate chemical stratification appears to occur during the winter turnover period, from December to March. Time series of each chemical data set data show that during stratification, the rate of carbon cycling increases within the hypolimnion, accompanied by an acidification and accumulation of CO 2 . Vertical profiling dives of Lake Travis resumed in February 2023 in order to characterize the lake stratification pattern under severe drought conditions and draw comparisons to the 2020/2021, pre-drought pattern. 

Mercedes Jordan

Mercedes Jordan is a first-generation geophysics (B.S.) honors student at the University of Texas at Austin’s Department of Earth and Planetary Sciences and an undergraduate research assistant at the University of Texas Institute for Geophysics. Mercedes’ research involves radar reflectometry, with current work focused on calibrating surface reflectivity from Kaguya’s Lunar Radar Sounder data using laboratory measurements of permittivity. During her time at UT, Mercedes has been recognized as a college scholar at the top of her class and has participated in the Undergraduate Honors Research Program. Mercedes hopes to pursue a doctoral degree in geophysics with a focus on planetary research following the completion of her undergraduate degree. 

Abstract:

The Lunar Radar Sounder (LRS) instrument aboard the Kaguya spacecraft collected extensive radar data during its mission, yet its utility for geologic interpretation was limited by its relative power scaling. Laboratory measurements of permittivity from recently collected Chang’E-5 samples allow for an estimation of the reflection coefficient at the landing site, allowing for an absolute calibration of Kaguya's LRS surface reflectivity. Focused on the Procellarum KREEP Terrane (PKT) region, this study aims to revitalize the LRS dataset, providing a more robust understanding of lunar surface materials within the first 50-75 meters of depth. Given PKT’s lack of rough and sloped terrain, it provides the perfect location for conducting absolute calibration of the signal through radar statistical reconnaissance (RSR) as most of the signal is coherent and specular. The methodology involved extracting surface reflectivity, fitting a distribution of amplitudes near the CE-5 landing site to a Rice probability density model, computing a gain correction factor, and applying this correction factor to the entire dataset. Preliminary results depict three distinct facies in the PKT region, associated with varying degrees of reflectance power. However, these heterogeneities in reflectance cannot be solely explained by surface geology as we see facies transition within the bounds of both mare basalt units. Mapping TiO2 abundance, FeO abundance, and roughness reveals dependencies on ilmenite content, with TiO2 showing a significant correlation with radar surface reflectivity.