In the Rocks: PDRF Uncovers Secrets of the Wasatch Fault

Robert McDermott Utah State University

Pittsburgh, Pennsylvania native Robert McDermott always wanted to “do science.” He began conducting experiments at a young age with his grandfather, a scientist for the National Energy Laboratory. After a brief stint as a music major at the University of Pittsburgh, McDermott changed his major to geology “on a whim,” and his love for geology was born.

“Science is a way of understanding the way things are put together and when you’re a geologist, the earth is your laboratory, like a grand experiment,” he said. “I want to understand it, and the key to understanding it is in the rocks.”

Now, McDermott is a Presidential Doctoral Research Fellow at Utah State University. Working with Dr. Alexis Ault in the Department of Geology, he researches low temperature thermochronology, the study of the thermal evolution of a region of the planet, and tectonics. He’s studying the Willard area of the Wasatch Fault, using uranium-thorium/helium (U-Th/He) dating to capture the big picture of the fault’s history, including its earthquakes.

The surface of fault damage zones, or fractures caused by tectonic activity, are coated in a mineral called hematite. When a fault moves, the hematite-coated rock surfaces are exposed to frictional heat. Current theory states that the temperature sensitivity of the hematite causes the uranium-thorium/helium system to reset during this temperature rise.

“By dating the hematite on the fault surface we can potentially date the earthquake,” McDermott said.

McDermott finds hematite samples dating from 1.5 to 10 million years old along the select zone of the nearly 230 mile-long (370 km-long) fault. He spends the majority of his field time hammering rock samples out of an outcrop with a hammer he lovingly refers to as “Das Beef Cake.”

He uses a dremel tool to separate the hematite from the rock, which is then flown to a helium lab designed to measure noble gases at the University of Arizona. McDermott said the samples are “zapped with a laser,” and de-gassed of helium, then dissolved in acid and put in a machine that measures the thorium helium, dating the sample.

While some faults are very active and create earthquakes, some haven’t moved for millions of years; McDermott said brittle fracture processes associated with faults are often poorly dated. But the pilot dating samples of Ault and McDermott’s endeavors look promising.

While this method could potentially lead to predicting earthquakes, McDermott says the science isn’t quite ready.

“It’s a newer application of the method so a lot of what we’re doing is trying to figure out the nitty-gritty of what the data means,” he said.

Four years from now, McDermott sees himself in the realm of academia, teaching classes, mentoring students and conducting research. Until then, he’s grateful for the support he receives as a PDRF to strengthen those skills.

“If I’m being honest, a good program will first and foremost let you focus on your research without having to worry about much else.”

Learn more about McDermott’s research with Dr. Ault.