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'Trail of Time' opens at Grand Canyon National Park

October 21, 2010

Acting upon the Grand Canyon’s potential for public geoscience education, ASU scientists have coordinated the construction of the world’s largest geoscience interpretative exhibit: the Trail of Time. This interpretative walking timeline trail focuses on the canyon’s vistas and rocks, and aims to guide visitors toward a better understanding of time.

After 15 years of work and all the accompanying trials and tribulations of putting together a major partnership, most people would be happy simply snipping a ribbon to signal the project’s completion. The official opening of the Trail of Time, however, went far beyond a basic dedication ceremony, as project organizers brought together an impressive gathering of high-profile geoscientists, informal geoscience education researchers and science interpreters for a three-day symposium. Speakers discussed at length how people understand complex topics such as geologic time.

Karl Karlstrom and Laura Crossey of the University of New Mexico, and Steve Semken of Arizona State University worked as the project’s principal investigators. Michael Williams of University of Massachusetts was a close collaborator and Judy Bryan, chief of interpretation at Grand Canyon National Park, was the primary collaborator between the team and the National Park Service.

Telling (geologic) time

It took a lengthy 6 million years to carve the world-renowned steep-sided chasm, but the canyon actually is considered a very young feature geologically. What often is overlooked by millions of Grand Canyon visitors each year is the fact that the rocks exposed in it are about 2 billion years old. The age of the canyon pales in comparison to the age of the rocks within it.

But in our instantaneous society, where we expect immediate e-mail responses and depend on fast-food meals, how do you make "millions of years" have any meaning? To us, 1 million seems unimaginably long. Time is easily comprehended when it is measured in increments of years. While this unit is adequate when looking back on recent human records, it is insufficient for discussing geologic time, which spans 4.6 billion years. Conceptualizing and comprehending time when it spans anything more than a few centuries is a challenge for many people.

A grasp of the magnitude of geologic time is the foundational knowledge needed to construct an understanding of many aspects of our planet and the universe, yet it is something that most people rarely engage with or are even taught.

“Our hope is that Trail of Time visitors will walk away with a better understanding of how human timescales relate to geologic timescales,” said Semken, associate professor in the School of Earth and Space Exploration in ASU’s College of Liberal Arts and Sciences. “Geologic time is one of the most significant ideas that science has ever come up with. It’s something that you have to learn in order to really understand other key scientific concepts, such as biological evolution.”

National parks are the premiere locations in the world in terms of informal science education, and they are sometimes the only places where people go to learn science, especially earth science. These parks play an enormous role in educating broad cross-sections of the public about earth science, the principles of earth science, and earth science processes.


Karlstrom, Crossey and Michael Williams of the University of Massachusetts, all Grand Canyon geological researchers for decades, first envisioned turning a Grand Canyon hiking trail into a walking timeline that would represent the magnitude of geologic time. Semken joined the team several years later to help realize the potential of the project for research on how people learn about geologic time.

The layout of the trail was based upon simple math. Since the oldest rocks at the Grand Canyon are 1.8 billion years old (1,800 million years), this means 1,800 meters of trail (almost 2 kilometers) is needed to represent the history of the Grand Canyon. At every meter of its length, the trail is marked with inset bronze disks, each meter symbolizing 1 million years of Earth’s history.

Imagine that one long stride represents a million years, and you have to take 2,000 of those strides just to get to the age of the oldest rock in the Grand Canyon, which is less than half the age of the Earth. By walking this timeline trail, visitors get a physical as well as intellectual sense of how long geologic time is.

Funded by the NSF Informal Science Education Program, this was the first time that any National Park Service site has participated in a project of this type. Many other types of exhibits and curricula have been created to address geologic time, but there is nothing comparable in scale or scope to the Trail of Time, according to Semken.

Future implementation

For Rebecca Frus, a graduate student focusing on earth science educational research in the School of Earth and Space Exploration, the Trail of Time now is officially part of Grand Canyon National Park, but that doesn’t mean the project is complete.

“Most people here would agree that it’s not done," said Frus, who is writing her thesis under Semken’s supervision on how visitors understand the relationship between the horizontal timeline and the vertical strata represented in the walls of the Grand Canyon. "Some people still have to work on the trail, and other people like me are still finishing research. The opening is definitely a significant milestone, and it’s nice to say the ribbon has been cut and it’s now officially part of the park but it doesn’t feel done.”

Nearly 50 park service employees from across the country attended, with several expressing interest in exporting the Trail of Time idea to other national parks and incorporating the concept in the local landscape.

Work also remains to be done on the web-based Virtual Trail of Time, which will be a resource available to learners who cannot visit Grand Canyon in person, and will also enhance the learning experience for those who do hike the Trail.