Mesa State on the Mississippi

Mesa State on the Mississippi

You know you are in Louisiana when cafes sell PoBoys and Muffelattas, big fish include alligator gar, grocery stores have names like Piggly Wiggly, fried catfish is a daily staple, farmers don't irrigate, rivers dwarf the Colorado and rain falls in buckets, not drops.

This is the natural and cultural setting for ongoing research on the geologic history of the Mississippi River by geology associate professor Andres Aslan and Mesa State College students. For the past several years, Aslan has taken students to Louisiana to try and reconstruct the history of the Mississippi River over the past 40,000 years. In doing so, Aslan and his students hope to provide insight into how the Mississippi River responds to changes in climate, sea level, and anthropogenic influences.

Work on this project began in 1992 when Aslan was a geology graduate student at the University of Colorado at Boulder and was studying the Mississippi River for his dissertation. This work evolved into a passion to learn more about the long-term history of the largest river system in the United States. Big rivers require big teams of researchers and Aslan has worked very closely with Whitney Autin, a geology professor at SUNY-Brockport in New York. Together, Drs. Aslan and Autin spend several weeks each summer working with students mapping the floodplain and using a hydraulic drilling rig to acquire core samples of floodplain sediments and soils. By examining the sediments and radiocarbon-dating wood and plant fragments in the cores, the research team reconstructs ancient locations of the Mississippi River and the time intervals when these ancient Mississippi channels were active. The field work allows students from Mesa State and SUNY-Brockport to work together, and has also introduced them to geology professors and students from other universities such as the University of Illinois at Chicago and the University of Nebraska at Lincoln, where similar research is being conducted.

In addition to the summer field work, Mesa State students were able to take structured research courses focusing on the Mississippi River in 2001 and 2002 that allowed them to work closely with Aslan performing laboratory analyses on samples brought back to Mesa State. Students determined sediment grain sizes, used a state-of-the-art x-ray diffractometer to identify the mineralogy of the sediments, and helped prepare samples for geochemical and
radiocarbon analyses.

Funding for this project, including payment of student expenses and laboratory supplies and analyses, has come primarily from an American Chemical Society Petroleum Research Fund grant awarded to Aslan. Results of the project have included professional presentations at national geological meetings in Boston and Denver, and several publications are in preparation. A total of 15 students have worked on the Mississippi project with Aslan, including students from the geology, environmental science, and biology programs. These students include Alex Garhart ('03, geology), Christine Cordova (geology), Kim Garhart ('02, geology), Alexis Hosack ('02, geology), Tarin Boxberger ('03, geology and environmental science), Jacob Rundell ('03, geology), Hannah Shields ('02, geology minor), Emarae Garcia ('03, biology), Tim Dobransky ('01, environmental science), Clem Rodriguez ('01, environmental science), Rick McClain ('02, environmental science), Ammer Swajy ('02, environmental science), Adam Thomas ('03, environmental science), Angie Campbell ('03, environmental science), and Jean Carrier ('03, environmental science). Of the students involved in this project, several have gone on to graduate school whereas others have taken jobs in the private sector or gone on to teach.
Alex Garhart, one of the participating students, credits the experience with providing him with some great field experience. "My initial reason for going on this trip was to improve my graduate school resume, but I gained so much more than just a resume builder," he said. "Having the chance to drill core samples, do geologic write-ups and just get my hands dirty was quite an eye-opener. It's one thing to learn about something in a classroom setting and a whole other thing to put it into practice in a field setting."

Satellite image of the Lower Mississippi Valley in Louisiana.

Satellite image of the Lower Mississippi Valley in Louisiana. The Old River Control Structure prevents the Mississippi River from abandoning its course past Baton Rouge and New Orleans, LA, and flooding the Atchafalaya Basin and Morgan City, LA.

Mississippi Student Participants

2002 Mississippi Field Crew, including Mesa State and SUNY-Brockport students and faculty. Kneeling in the front row: Angie Koontz (environmental science), Emarae Garcia (biology), and Jean Carter (environmental science). Middle of back row: Dr. Andres Aslan.

Mississippi River

Describing a cutbank section of 30,000 year old Mississippi River deposits in south Louisiana.

Aerial Photo of the Mississippi River

Aerial photo of the Mississippi River.

The most recent work has focused on the process of avulsion, which describes large shifts in the course of major rivers such as the Mississippi. Mississippi avulsions have occurred at least five times over the past 5,000 years in south Louisiana but the causes of this important process are not well understood. Aslan and his students are trying to improve their understanding of Mississippi avulsion by sampling the floodplain in the vicinity of the world-famous Old River Control Structures. These structures are large headgates that are responsible for preventing the Mississippi River from flowing down the Atchafalaya River and abandoning its present-day course to the Gulf of Mexico. The floodplain near the Old River Control Structure provides a unique opportunity to study the conditions that lead to avulsion because left unchecked, the Mississippi River would undoubtedly avulse and follow the shorter, more southerly course of the Atchafalaya River to the Gulf of Mexico. This shift in the river would be disastrous for the United States because, in addition to loss of life and property along the Atchafalaya River, cities such as Baton Rouge and New Orleans would no longer have access to the Mississippi River.

One of the important geologic aspects of the floodplain near Old River is the presence of abundant sand deposits that may hold a key as to why the Mississippi River could avulse in this area. Sand is easy to erode and would allow the Mississippi River to easily carve a channel sufficiently large to capture the entire flow of the Mississippi and lead to an avulsion. In addition, there are several large abandoned Mississippi River channels immediately downstream of the Old River area that would also facilitate a Mississippi avulsion. These factors may play a key role in both the present-day potential for a Mississippi avulsion in the Old River area as well as more ancient examples. These ideas contrast with more traditional theories that typically cite gradient differences to explain avulsions. While the Atchafalaya River's gradient is almost three times steeper than the Mississippi's, gradient advantages such as this exist throughout the lower Mississippi Valley. If gradient differences were the sole cause of avulsions, we would expect to see the Mississippi River avulsing each time there was a major flood. In reality, avulsions are rare, so factors other than gradient differences must be important.

So what's next? Not surprisingly, Aslan has become fascinated by the Colorado River and its rich geologic history. In fact, one of the critical questions that Aslan hopes to address in the near future is how old is the Colorado River? Aslan spent much of the past summer laying the groundwork for this project and looks forward to continuing to work with Mesa State students, Amanda Huddleston and Sherry Hale, in our "backyard."

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