About

The nature of tectonic processes during early Earth history is still poorly understood. It is still not known when continents started forming and when plate tectonics commenced. Due to the higher heat flux from the mantle, plate tectonics may not even have been possible and other tectonic processes may have dominated. One problem in studying early Earth history is the scarcity of rocks older than 2.5 billion years ago (Ga) and the total absence of rocks older than 4.0 Ga. To understand the nature of the crust and crustal processes in deep time, the Drabon lab investigates the mineral zircon. Zircons are ubiquitous in felsic rocks and detrital zircons as old as 4.3 Ga have been found in sandstones. Their geochronology, isotope geochemistry, and trace and rare earth element geochemistry can help unravel the nature of the crust and tectonic processes during this time period.

Previously, REU students worked in the Drabon lab to analyze 3-billion-year-old zircon. Students applied a variety of imaging and analytical techniques to understand the genesis of zircons, draw conclusions about their source rock, and constrain crustal processes during the early Earth.

Earthquakes serve as sporadic and important reminders that the Earth is in motion. While the shaking associated with earthquakes causes significant damage, these brief intervals of energy release are a byproduct of the slow build-up of elastic strain over decades and centuries. The central goal of work done in the Meade group is to integrate computational fault system models with geodetic observations of slow surface motions to characterize the present state and future activity of seismically active fault systems across the globe.

Previously, REU students contributed to development of data and models that can help forecast the locations and magnitudes of future earthquakes.

Stress within the Earth gives insight into its dynamic history. Tectonic plates impart substantial stress and their direction and strength are indicative of the dynamics of the plates. The Ishii group uses seismic recordings to investigate the stress distribution through “splitting” of seismic waves. Japan is an ideal location for this study for two reasons. It is one of most tectonically active regions, with a substantial number of earthquakes, both small and large. It is also one of the best monitored regions in the world. For example, the Hi-net seismic network consists of nearly 800 stations located almost evenly throughout Japan, providing high-quality seismic wave observations.

Previously, REU students used an earthquake catalog to find events that are likely to provide stress information around Japan, and obtain the corresponding data. 

Some of the most severe storms on Earth occur in inland continental regions (such as the central United States), far from oceans. The land surface underneath these storms – in particular, the amount of moisture in the soil – plays a critical role in determining their intensity, duration, and frequency. Yet many of the key physical mechanisms linking the land surface to the atmospheric state are poorly understood, which contributes to inaccurate forecasts of severe storms over land. The McColl group has expertise in using high-resolution numerical simulations and global satellite observations to understand land-atmosphere interactions, and their impacts on storms.

Previously, REU students learned to use cloud-resolving simulations of storms over land. By interpreting model output, students investigated the role of changing land surface features on storm initiation and development.

Research in the Martin lab focuses on air pollution and particulate matter and their effects on climate change. Martin led the Green Ocean Amazon Experiment (GoAmazon2014/5) which investigated the effects of human activities on air quality, weather, terrestrial ecosystems, and climate in a tropical, forested context. Recently, the Martin lab has focused on studying fundamental physical properties of particulate matter that have downstream effects on particulate loadings and the atmospheric processing of pollutants. Questions of interest regarding these physical properties include: For a given particle composition, is the particle a solid, semisolid, or liquid? Does the particle have a uniform, well-mixed composition or has the particle separated into two or more separate phases? How do these properties affect the amount of particulate matter or the impacts of this particulate matter on the climate?

Previous REU students conducted laboratory studies where they generated model aerosol particles in a flow tube or environmental chamber. In addition to analyzing these particles with standard aerosol analytical techniques that characterize the number and size of the particles, the students determined particle physical properties using a recently developed instrument called the fluorescence aerosol flow tube. Students varied the size and chemical composition of the particles and determined the effect that each of these have on the viscosity of the particles and whether the particles phase separate or remain homogenous. 

The Mickley group investigates the links between climate change, fire activity, and smoke pollution. Past research has focused on the health impacts of biomass burning in Brazil, India, and Indonesia and on the impacts of climate change on wildfire frequency and extent in the western U.S. In the western United States, both climate change and fire suppression have likely contributed to the recent dramatic increase in fires. In particular, the legacy of 20th-century fire suppression has led to large accumulation of underbrush, providing abundant fuel and increasing the risk for subsequent fires of large size. Marlon et al. (2012) showed that the western United States is under a “fire deficit” regime which can be traced in large part to active fire suppression as more people move into fire-prone areas. These authors further argued that climate change is enhancing the fire deficit in U.S. forests, raising the risk of large and uncontrollable fires in the future atmosphere.

REU students previously investigated land management approaches that promote prescribed fires of moderate intensity. For example, Indigenous people in the West and worldwide have traditionally used prescribed burning, sometimes called cultural burning, to manage land and limit the frequency of large fires. So far, most scientific evidence of the benefits of prescribed burning in the West has come from a small number of case studies. REU students used satellite measurements over the 2003-2020 era together with on-the-ground estimates of area burned to probe the utility of prescribed burning in limiting large fires. Particularly useful were records from the Bureau of Indian Affairs, which show that the spatial extent of prescribed fires across Native American territories has increased 4% yr-1 from 1998 to 2018.

Human activities and modern industry have released large quantities of heavy metals and approximately 100,000 synthetic organic compounds to the global environment. When present in the human body, these environmental toxicants have been linked to many negative health effects, such as the global pandemic of neurocognitive deficits in children, increased risks of cardiovascular disease, and a rapid rise in immune disorders. However, the links between human activities that release environmental toxicants and their adverse impacts on health have not been well established because chemical cycling through the physical environment and food webs is not well understood. Research in the Sunderland lab aims to address this gap through interdisciplinary investigations of the exposure pathway for toxicants.

REU students previously studied factors affecting the transport and distribution of heavy metals and persistent organic pollutants in the open ocean and coastal marine ecosystems. The Sunderland group uses a combination of field, lab, and modeling tools that students learned to use. Field and lab research focused on understanding relationships between environmental properties (e.g., dissolved organic carbon, temperature, productivity) and chemical speciation/ bioavailabilty of trace metals and organic compounds. Students measured reaction rates and concentrations in environmental samples that can be used to parameterize and evaluate modeling simulations. They had access to the diverse instrumentation in the Sunderland lab including HPLC-MS/MS, ICP-MS, and MC-ICP-MS.

Better knowledge of Earth’s climate in the past is important for predicting the behavior of the climate system under CO2 levels projected for the coming century. Sea surface temperature (SST) records, proxy approaches to reconstructing CO2 levels (pCO2) during past warm periods in Earth history, and measures of the ecology and productivity of the marine ecosystem together provide a picture of the marine paleoenvironment. The Pearson group studies these questions using the organic remains of marine organisms that are exported to marine sediments, specifically through approaches that utilize lipid molecules of high preservation potential. Recent work has demonstrated that microbial lipids of Thaumarchaeota play a dual role as SST paleothermometers and potential tracers for the inorganic carbon loading of the atmosphere-ocean system, including dissolved inorganic carbon (DIC) and pCO2 concentrations and sources. Although many types of SST paleothermometers exist, as do several pCO2 paleoproxies, few records currently attempt to cross-correlate these different approaches within the same sediment record or same sediment basin. Recent work from the Pearson lab shows the value of these high-resolution comparative exercises, including the ability to examine the responsiveness of the marine system to orbitally driven climate cycles.

REU students continued this work by implementing an “all-in-one” method that obtains three different SST proxy records simultaneously in a single analysis of a sediment organic extract. Using this method, we can evaluate how all three SST signals interact across time periods orgeographic locations. Our areas of focus include the boundary region of the Southern Ocean and southern Atlantic Ocean, influenced by the path of the Agulhas current, as well as evolution of the zonal gradients of the tropical Pacific Ocean. In these regions, SST proxy records may be influenced by an overprint of changing marine ecology and data from different paleothermometers may not be interchangeable due to biotic effects. The student worked with a group member to deconvolve the multivariable nature of these combined signals.

Research in the Tziperman group focuses on ocean, atmosphere and climate dynamics, trying to understand physical processes that affect Earth’s climate on time scales of a few years to millions of years. Climate variability results from a rich set of nonlinear, sometime chaotic, physical interactions of the oceans, atmosphere, and at times the biosphere as well. Some of the very basic questions in this research area are still unanswered – e.g., why were there ice ages, why is El Niño difficult to predict, what future warming can we expect in a century, how can we understand specific observed features of past warm climates millions of years ago, and what can these features teach us about the future? The Tziperman group uses simplified mathematical models of a given climate phenomenon to understand the mechanisms in question in detail, together with more realistic state-of-the art simulations for testing ideas developed using simpler models.

REU students participated in climate dynamics research activities, especially those focused on ocean processes. Possible project topics ranged from global warming, El Niño, the large-scale oceanic thermohaline circulation, and past cold climates such as the ice ages. Typical projects involved python programming and the analysis of observations or the output from climate models.