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USGS Science Enriched by Mendenhall Research Fellows

Mendenhall Research Fellows, who come to USGS through the Mendenhall Research Fellowship Program, are bringing new talents and skills to the Coastal and Marine Geology Program. 

This article is part of the March 2017 issue of the Sound Waves newsletter.

Mendenhall Research Fellows are bringing new talents and skills to the USGS Coastal and Marine Geology Program. They come to us through the USGS Mendenhall Research Fellowship Program, which gives recent Ph.D. graduates the opportunity to conduct concentrated research with USGS professional staff.

"The program provides postdoctoral research fellows with experiences that enhance their personal scientific skills and accomplishments," said Rama K. Kotra, Deputy Director of the USGS Office of Science Quality and Integrity and manager of the Mendenhall Program. "At the same time, the USGS benefits from the new ideas and skill sets that Mendenhall Fellows bring to the USGS to help us in advancing our scientific goals."

These Mendenhall Research Fellows joined the Coastal and Marine Geology Program in 2015 and 2016:

A man stands in the cockpit of a boat wearing a black full-body wetsuit, diving belt, and a diving helmet.
Mark Buckley prepares to deploy wave and current gauges in the surf at the Ningaloo Reef UNESCO World Heritage Site in northwestern Australia. Photo credit: USGS.

Mark Buckley earned his Ph.D. at the University of Western Australia, where he examined the impact of waves on fringing coral reefs. As a Mendenhall Fellow, Mark is investigating the fundamental processes that govern water and sediment movement on coral reefs. His goal is to better understand the geologic and oceanographic controls on the health and sustainability of coral reef ecosystems, as well as the role of reefs in protecting coasts from flooding and erosion by storm waves. Mark's research will advance our understanding of these complex systems and improve numerical models used to predict the effects of future storms and sea-level rise. Mark works at the Pacific Coastal and Marine Science Center in Santa Cruz, California, with his USGS advisor, research geologist Curt Storlazzi. In his free time, he enjoys surfing, kite surfing, sailing, mountain biking, and camping.

Amy Gartman earned a Ph.D. in oceanography at the University of Delaware, where she studied hydrothermal vents, fissures in the seafloor that emit hot, mineral-laden water. Before coming to the USGS, she studied microbe-mineral interactions at Harvard University. For her Mendenhall research, Amy is investigating the formation and dissolution of seafloor massive sulfide deposits, which form mounds and extensive aprons around high-temperature hydrothermal vents in every ocean. The rapid mixing of cold, oxygenated seawater with hot, metal- and sulfur-rich vent fluids precipitates abundant minerals, forming the charismatic "black smokers." Companies are likely to mine seafloor massive sulfides soon at sites where hydrothermal vents are no longer active. Crushing during mining will release a new class of particles, different from the natural ones in hydrothermal "black smoke." Amy is characterizing both classes of particles to compare how they fare in seawater. She's also looking at minerals that exist in low concentrations in these systems and may be toxic, technologically important, or useful as tracers. In October 2016, Amy collected fresh samples of seafloor massive sulfide deposits during a research cruise to the East Pacific Rise. She works at the Pacific Coastal and Marine Science Center with her USGS advisor, research geologist Jim Hein. She writes, "When I'm not at work or in the field, I like to spend as much time outdoors as possible, hiking, swimming, and exploring the California coast."

Shawn Harrison earned his Ph.D. from the University of Waikato, New Zealand, where he investigated sediment movement on ebb-tidal deltas, large accumulations of sand that form at the mouths of estuaries and tidal inlets. After completing his Ph.D., Shawn studied the migration of sand ripples across the continental shelf at Fire Island, New York, with John Warner and Jeff List of the USGS Woods Hole Coastal and Marine Science Center in Woods Hole, Massachusetts, and Peter Traykovski of the Woods Hole Oceanographic Institution. As a Mendenhall researcher, Shawn investigates how sediment moves between subtidal portions of deltas and adjacent beaches, and how the shape of a delta impacts those pathways. Improved understanding of the movement of sediment will help communities manage their coastal resources, such as harbors and beaches, and improve the efficiency of maintenance operations. Shawn works at the USGS Pacific Coastal and Marine Science Center with research geologist Jon Warrick and research oceanographer Guy Gelfenbaum. He is active in the Coastal Imaging Research Network and enjoys kite-surfing, bicycling, and hiking with his two kids.

A woman in casual clothes and a purple jacket stands on a dock in front of a dark blue RV with Atlantis painted  on the hull
Amy Gartman collected fresh samples of seafloor massive sulfide deposits during a research cruise to the East Pacific Rise on the research vessel Atlantis. Photo credit: USGS.
A man in a blue jacket wearing a GPS backpack holds a walking stick on a beach with calm surf in the background
Shawn Harrison uses a GPS-equipped backpack to measure sand elevations during a post-storm survey of beaches in Santa Cruz, California. Photo credit: USGS.


A man in jeans with a red backpack writes in a notebook on a mostly bare grey hillside
Matt Malkowski mapping Cretaceous deep-water landslide deposits in the southern Patagonian Andes. Photo credit: USGS.

Matt Malkowski earned his Ph.D. from Stanford University, where he investigated the influence of previous geologic events on the movement of sediment from mountains to ocean basins. For his Mendenhall research, Matt is studying the geologic evolution of the Bering Sea and its margins. He aims to better understand past and present processes of sediment erosion, transport, and deposition, and what these processes mean for submarine landslides and offshore resources. Matt's research will yield insight into processes that shape continental margins and provide a more detailed picture of how fluctuations in climate, sea level, and sediment supply affect the distribution of deep-sea sediment. His findings could also help determine the extent of the U.S. "extended continental shelf," where the nation can claim sovereign rights to seabed resources under the Law of the Sea. Matt works at the Pacific Coastal and Marine Science Center with research geologists Ginger Barth, Katie Maier, and Amy East. He has two additional USGS advisors at the Woods Hole Science Center: research geologists Debbie Hutchinson and Jason Chaytor. He writes, "When I'm not doing geology, I spend most of my time training and working with my mountain rescue team (search and rescue), having adventures with my dog Frida, skiing, climbing, playing basketball, gardening, and taking care of chickens."

Tim Nelson earned his Ph.D. at the University of South Carolina, where he studied the formation of seafloor ripples and their effect on turbulence and sediment in overlying water. As a Mendenhall Fellow, Tim studies how mixtures of sediment and oil move in the ocean environment. After events like the 2010 Deepwater Horizon blowout, spilled oil commonly mixes with sediment in the surf zone, forming a 70- to 80-percent sand mixture that sinks to the seafloor. These sand-and-oil agglomerates range in size from centimeter-scale patties to meter-scale mats. The smaller agglomerates can be transported onshore and alongshore. Numerical studies have found that sand-and-oil agglomerates are likely to become buried and re-exhumed by moving sand. These processes can result in concealment, exposure, and potential transport of the agglomerates and re-oiling of previously cleaned beaches. Tim runs experiments on artificial sand-and-oil agglomerates of various sizes, shapes, and densities in an oscillatory flow tunnel. The data from these experiments will improve numerical models that predict how sand-and-oil agglomerates move and interact with the seafloor—information that can assist oil-spill-remediation efforts. Tim works at the St. Petersburg Coastal and Marine Science Center in Florida. His USGS advisors are research oceanographers P. Soupy Dalyander, Nathaniel Plant, and Joseph Long in St. Petersburg, and research oceanographer Chris Sherwood at the Woods Hole Coastal and Marine Science Center. Tim's hobby is nature photography.

Dan Nowacki earned a Ph.D. in oceanography at the University of Washington, where he studied sediment-transport processes in tidal environments of the Pacific Northwest, Brazil, and Vietnam. As a Mendenhall Research Fellow, Dan is using a combination of field measurements and numerical modeling to understand how submerged aquatic vegetation modifies storm waves and their ability to move sediment in shallow-water environments. Using an array of field instruments, he is also measuring long-term sediment loss from Grand Bay, a rapidly retreating tidal salt-marsh complex bordering Alabama and Mississippi on the Gulf of Mexico. These projects will help quantify the resilience of coastal areas to large storms and could ultimately help coastal planners understand the role of natural ecosystems in storm protection. Dan works at the Woods Hole Coastal and Marine Science Center with USGS research oceanographer Neil Ganju. When he's not working, Dan enjoys running an all-volunteer community bike shop, exploring the outdoors, restoring old boats, and playing the banjo.

A man in an orange shirt stands in front of a machine with many wires. A poster is on the wall behind him.
Tim Nelson uses a combination of fieldwork and lab experiments to investigate the interaction of flowing water and sediment. Photo credit: USGS.
A man crouches over a marine instrument set on the grass
Dan Nowacki preparing instruments for deployment in Chincoteague Bay. Photo credit: USGS.

Ferdinand Oberle earned his Ph.D. from the Center for Marine Environmental Sciences (MARUM) at the University of Bremen, Germany, during which he spent one year working for the department of Marine Chemistry and Geochemistry at the Woods Hole Oceanographic Institution in Massachusetts. Ferdinand studies the interaction between groundwater and seawater. The flow of groundwater directly from an aquifer into the ocean is called "submarine groundwater discharge." Submarine groundwater discharge not only delivers freshwater to the ocean, it can also bring chemicals from the land, such as nitrogen and phosphorus from fertilizers. This largely invisible process has important impacts on coastal waters. Ferdinand's Mendenhall research focuses on measuring submarine groundwater discharge in Pacific atolls, Arctic permafrost, and Hawaiian coral reef settings. He uses geophysical, geochemical, and numerical techniques to make and analyze these measurements. He also uses airborne thermal imaging to rapidly identify where groundwater is entering seawater, a method made possible by temperature differences between the two types of water. Ferdinand seeks to improve understanding of how seawater and groundwater interact, whether and how humans have changed these interactions, and how such changes affect coastal communities. Ferdinand works at the Pacific Coastal and Marine Science Center, where his USGS advisors are research oceanographers Nancy Prouty and Peter Swarzenski. He writes, "Outside of my work you can find me windsurfing, mountain biking, hiking, playing basketball, or taking pictures of birds. I also enjoy practicing cello and guitar, and I follow the world of science/nature documentary film making."

Davina Passeri earned a Ph.D. in civil engineering from the University of Central Florida. She uses numerical and statistical modeling to determine how future sea-level rise is likely to affect tides, waves, and hurricane storm surge. Her Ph.D. thesis focused on tidal changes that sea-level rise may cause within embayments in the northern Gulf of Mexico—changes that could affect coastal navigation, communities, and ecosystems. For her Mendenhall research, Davina is examining the response of Dauphin Island, a barrier island off the Alabama coast, to hurricane storm surge under various future sea-level rise scenarios. For example, if Hurricane Katrina hit in 2050 under 50 centimeters (20 inches) of sea-level rise, how much flooding, dune erosion, and overwash could residents expect? The results of her simulations will provide a better understanding of the effects of sea-level rise and can be used to project future damage or loss of property, infrastructure, and habitat. Davina works at the USGS St. Petersburg Coastal and Marine Science Center in Florida with USGS research oceanographer Nathaniel Plant. In her spare time, she enjoys working out, going to the beach, and traveling.

A close up of a smiling dark-haired man in a red shirt and yellow hard hat stands with a research vessel on the sea behind him
Ferdinand Oberle about to embark on the German research vessel Meteor for a study of seafloor sediment off the northwest coast of the Iberian Peninsula. Photo credit: USGS.
A woman in a white blouse rests her arm on a wooden rail with thin trees in the background
Davina Passeri uses computer modeling to project what would happen if a hurricane struck Dauphin Island, a barrier island off the Alabama coast, at a range of sea levels higher than today's. Photo credit: USGS.

Kenny Ryan earned his Ph.D. at the University of California, Riverside, where he combined earthquake and tsunami simulations with case studies off southern Alaska and southern California to improve understanding of the earthquake-tsunami system. Kenny's Mendenhall research centers on modeling how earthquake rupture progresses during a quake and how that rupture affects overlying water. This dynamic modeling provides a new way to simulate tsunami generation. It is a more realistic approach than traditional methods of modeling tsunami generation in that it combines the processes associated with earthquake rupture in the solid earth with hydrodynamics (water movement and the forces associated with it) in the water above the earthquake. Kenny provided modeling of the hypothetical tsunami-generating earthquake used in the Science Application for Risk Reduction (SAFRR) Tsunami Scenario. He continues this research during his Mendenhall fellowship, examining the effects of stress variations along the Alaska-Aleutian subduction zone on earthquake rupture, tsunami generation, and local tsunami propagation. He will also examine the unusual 2012 Haida Gwaii earthquake—a complex tsunami-generating event off British Columbia that produced significant slip near the seafloor. Kenny's USGS advisors are research geophysicists Eric Geist and Tom Parsons of the Pacific Coastal and Marine Science Center, and research geophysicist Ruth Harris of the Earthquake Science Center. He writes, "In my free time, I like to go hiking, am learning to play drums, and enjoy whiskey tastings."

Maureen Walton earned her Ph.D. at the University of Texas Institute for Geophysics, where she used a variety of marine geophysical data—including seafloor bathymetry, seismic-reflection profiles (imagery of sediment layers beneath the seafloor), and earthquake data—to study sediment deposition and earthquake faults offshore of southeast Alaska. Maureen's Mendenhall research focuses on fault deformation off southern California, where she is looking at potentially active offshore fault strands related to the San Andreas fault system. She is using new USGS high-resolution seafloor bathymetry and seismic-reflection data from the Catalina Basin, about 50 kilometers (30 miles) offshore of Los Angeles, to study geologic hazards such as earthquakes and submarine landslides. Maureen is excited to be analyzing the new data and seeing the basin in new ways, and looks forward to providing new results on the history of fault deformation and modern geohazards. She works at the Pacific Coastal and Marine Science Center with her USGS advisors, research geophysicists Danny Brothers and Tom Parsons and research geologist Katie Maier. Maureen's interests include walking and running along the coast with her husband and 1-year-old husky puppy, as well as hiking, camping, cooking, singing, and keeping up with critically acclaimed films. Now that she has moved to California, she's working on adding surfing, skiing, and mountain biking to the list.

A slender young man stands on a steep hillside wearing a black backpack
Kenny Ryan hiking at the 49 Palms Oasis in Joshua Tree National Park, California. Photo credit: USGS.
Close up of a smiling woman in coat and hat in front of a fjord with a glacier and mountains in the background
Maureen Walton in front of the Tyndall Glacier in Taan Fjord, Alaska, during a study of earthquake hazards off southeast Alaska. Photo credit: USGS.

Please welcome these additions to the Coastal and Marine Geology Program. The talents and fresh ideas of these researchers are a vital resource for the future of USGS science.

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