Interpreting Geologic Time in Natural Landscapes

Steve Semken, School of Earth and Space Exploration, Arizona State University

Geologic time is so fundamental to the Earth, environmental, biological, and space sciences that anyone who teaches in these disciplines is likely to have some interest in student cognition of deep time and in effective teaching about time, process, and evolution. As many colleagues do, I draw on cognitive studies, published best practices, and my own professional experience in teaching about time in my geoscience courses. But I am also very concerned about how inability to grasp the concept of deep time contributes to widespread public misconceptions about geological and biological evolution, climate change, sustainable lifeways and economies, and the like. No matter that geologic time is specifically addressed in national standards for K-12 education and in numerous scientific literacy documents; most people will never formally engage with the concept because they will not study Earth science in high school or beyond.

Hence, one of my primary research interests is in effectively teaching the public about geologic time and change through free-choice (informal) education in the outdoors, by means of the natural landscapes of National and State Parks and other protected public lands. These spectacular, revered landscapes encode vast intervals of geologic and environmental history while also displaying the geomorphic processes at work in the present. They offer rich opportunities for informal learning about geologic time, processes of change, and the relationship between human and geologic time scales. In these settings the teaching practice is more commonly known as interpretation. This interest grew from my work in sense of place and place-based teaching and learning.

Most of my group's work on informal education and interpretation related to deep time has been situated at the Trail of Time Exhibition ( at Grand Canyon National Park: the world's largest interpretive geoscience exhibition, which our team (led by Karl Karlstrom of UNM) designed, built, and formally opened in fall 2010. The heart of this exhibition is a horizontal scaled timeline laid out along 4.5 km of fully accessible trail along the South Rim of the Canyon, augmented by interpretive signage, viewing tubes, and alluring large specimens of every rock unit exposed in Grand Canyon. Extensive front-end, formative, and summative evaluation were essential to the project. We have used and continue to use the Trail of Time Exhibition, visited by millions each year, as unique field-based laboratory for research on the use of timelines and other analogical models for informal learning about deep time. I will discuss some of this work during the Teaching about Time Workshop, and invite all who can to join me on a visit to Grand Canyon and the Trail of Time itself (weather permitting!) after the Workshop ends.


Karlstrom, K., Semken, S., Crossey, L., Perry, D., Gyllenhaal, E. D., Dodick, J., Williams, M., Hellmich-Bryan, J., Crow, R., Bueno Watts, N., & Ault, C. (2008). Informal geoscience education on a grand scale: the Trail of Time exhibition at Grand Canyon. Journal of Geoscience Education, 56, 354-361.

Semken, S., Dodick, J., Ben-David, O., Pineda, M., Bueno Watts, N., & Karlstrom, K. (2009). Timeline and time scale cognition experiments for a geological interpretative exhibit at Grand Canyon. Proceedings of the National Association for Research in Science Teaching, Garden Grove, California.

Semken, S., Dodick, J., Frus, R., Wells, M., Perry, D., Bryan, J., Williams, M., Crow, R., Crossey, L., & Karlstrom, K. (2009, November-December). Studies of informal geologic time learning at the "Trail of Time" in Grand Canyon National Park. Informal Learning Review, 1(99), 1-5.

Crow, R., Karlstrom, K., Crossey, L., Semken, S., Perry, D., Williams, M., & Bryan, J. (2011). It's about time: Innovations in geoscience education at the Grand Canyon. Legacy, 22, 26-27.