Kevin Theissen

How the Earth Works

I grew up in south Minneapolis. From the beginning I was outdoors as much as possible exploring the world. I spent my time collecting bugs, climbing trees and observing both the large and small details of the natural world that existed in the urban environment. My father always has had a great love of the western United States, and my two younger brothers and I got to explore many spectacular landscapes and geological marvels on long summer road trips to the national parks of southern Utah and Arizona, the Canadian Rockies and the ruins of cliff-dwelling Native Americans. With this background, I arrived at Carleton College with the intention of majoring in a natural science. Although I started off with several courses in biology, my experience in an introductory geology course during my sophomore year was life-changing. Like many, I was inspired by a great teacher, the late Dr. Shelby Boardman, who got our class outdoors doing science for nearly every lab session. When I expressed interest, Dr. Boardman helped me find an internship opportunity with the U.S. Geological Survey in Denver, where I spent parts of three summers mapping some spectacular geology and doing an independent research project on the Montana-Idaho border. These field summers firmed up my growing interest in understanding how the Earth works.

A second significant experience came in a job as a teaching assistant for an off-campus interdisciplinary science course at Biosphere 2 Center in southern Arizona. Here, I worked for a small team of faculty who were linking desert geology, ecology and science policy in their instruction – much of which was based in the desert landscapes around us. During the year I spent with this program I met and observed top researchers who were using the unique enclosed environment of “the bubble,” as Biosphere 2 was known, to better understand the effects that rising levels of greenhouse gases were having on different natural processes such as plant growth in rainforests and coral reef development in the ocean. I realized that I wanted to contribute, in some way, to our understanding of global change. I was fortunate to be able to combine my interests in geology and global change in my Ph.D. research at Stanford University. There I used geological and chemical methods to explore ancient episodes of climate and ecological change in South America and Antarctica.

Throughout my career, I have used sediment cores from lakes as a way of exploring past change. I have closely studied cores from places as distant and remote as Tierra del Fuego and as local and accessible as the Minneapolis Chain of Lakes. An important insight that has come from this research is the sometimes-abrupt nature of climate and ecological change that is recorded in these cores. For example, I examined a 25,000-year-long core record from Lake Titicaca, a large lake on the Bolivian-Peruvian border, which showed ancient evidence for a series of extreme changes in lake level (fluctuations of 10-60 meters water depth) in as short as 50 to 75 years. These changes were driven by a series of naturally occurring solar cycles that influence the Earth’s climate, sometimes resulting in pronounced droughts or wet periods. As more records of past climate and ecological change are reconstructed around the world, we have found that these abrupt changes are more common than previously had been thought, and that they have previously affected areas with fast growing populations such as the American southwest. This line of research has been important because it has led to the understanding that these abrupt climate changes contributed to the collapse of ancient societies, such as the Mayan empire, and that such changes still hold the potential for significant disruption to society, particularly in the desert or near-desert regions of the planet.

Since joining the Geology Department at UST in 2003, my research has increasingly focused on examining records of the last 200 to 300 years from Minnesota lakes. This time period spans the “Anthropocene,” a term coined by scientist and Nobel Laureate Paul Crutzen for our most recent slice of geologic time. Crutzen feels – and I agree – that this is a period clearly distinguished by a significant human mark, if not domination, of the natural world. In nearly all of the core records my students and I examine from this time frame, large and abrupt changes are easy to see. These changes show up as significant jumps in erosion rates and in the supply of nutrients and contaminants reaching the lakes over the last 100 to 150 years during which population growth, industrialization and countless other human-related activities have accelerated. As I tell my students, lakes are environmental “beakers,” and our collective activities often have become apparent in greener, less healthy waters. People care about their lakes and natural spaces, and if they are given good information I think that they support efforts to protect them. This research is important because we can show the public what conditions were like prior to intensive human development and provide lake managers the information they need to better protect these important natural resources.

In my nearly 10 years at St. Thomas, students have been instrumental in all areas of my research, from field work to laboratory analysis to data interpretation and presentation of our findings at regional and national-level scientific meetings. I have been fortunate to have worked with a number of excellent students who are motivated by the same curiosity I have about global climate and ecological change and also by the desire to take steps towards addressing these challenges. I have long been interested in student attitudes about global climate change and I explored this through interviews, surveys and student work as part of a sabbatical research project. The good news is that a clear majority of students recognize the impact that we collectively have on the natural world, and many of them profess their strong desire to do something about it.

Kevin Theissen is professor of geology in the College of Arts and Sciences.

From Exemplars, a publication of the Grants and Research Office.