UMW Professor Publishes Paper in Centennial Volume on Montana Geology

Dr. Rob Thomas, from the University of Montana Western's Environmental Sciences Department, was recently published in the Centennial Geology Volume of the Montana Bureau of Mines and Geology for his work on the influence of the Yellowstone Hotspot on Montana geology over the last 17 million years of Earth's history. The paper is titled: “Middle Miocene Through Pliocene Sedimentation and Tectonics in Montana: A Record of the Outbreak and Passage of the Yellowstone Hotspot.”

UMW Professor Dr. Rob Thomas.

The Montana Bureau of Mines and Geology (MBMG) recently celebrated 100 years of service as Montana’s geologic survey. To celebrate the centennial, the MBMG decided to take on the massive undertaking of creating a two-volume set summarizing the state of geologic science in Montana. The project is in progress, with papers being released to the public in an online format at the following web address:

Volume I will include 17 papers that present Montana’s geologic history, and Volume II will include 11 papers that explore special topics related to our geologic resources. Production of “The Geology of Montana” relied on the contributions of geological researchers who were selected for this project based on their expertise in the various subjects covered.

Dr. Rob Thomas at the University of Montana Western, working with Dr. James Sears from the Geosciences Department at the University of Montana, were selected to summarize the state of knowledge on the geology of Montana from approximately 17 million to 2.5 million years ago. This is a period of time in Montana when many of the mountains and valleys we see today were forming, and the modern course of the Missouri River drainage was established. According to Thomas, his paper with Sears is “the product of decades of research by countless professionals and students.” Thomas said, “it was a great honor to be selected to summarize this very important period of time in the evolution of the Montana landscape.”

Stream-deposited ash from an eruption of the Yellowstone hotspot in Idaho some 10 million years ago can be found throughout southwest Montana. These spectacular towers of ash occur in the Blacktail area east of Dillon.

Mountain building in Montana was greatly influenced by the passage of the North American Plate over the Yellowstone volcanic hotspot. This active volcano is the world’s largest explosive volcano, stretching and breaking the crust in Montana into ranges and valleys as the plate moves to the southwest over the stationary hotspot. The evidence for the evolution of our landscape over the last 17 million years is the primary focus of the paper published by Thomas and Sears.

Coming soon from Dr. Thomas will be a paper on the geology of Montana between 541 to 485 million years ago, a period of time called the Cambrian. This was a time of vast tropical oceans teaming with trilobites, crinoids, brachiopods and other marine creatures. Thomas is working with MBMG geologist Katie McDonald on the paper, which should appear in the online volume late in the spring of 2021. Thomas is also the co-author of two of the popular Roadside Geology series of books, including the one for Yellowstone Country (2011) and Montana (2020).

The paper from Dr. Thomas and Dr. Sears is available in its entirety on the Geology of Montana website. For more information, please contact [email protected].