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Geoscience exhibit displays 'Trail of Time'

March 02, 2009

Spectacular in its depth and breadth of beauty and unequaled in inspirational power, the Grand Canyon is a natural masterpiece. It took a lengthy 6 million years to carve the world-renowned steep-sided chasm but with its one-in-a-million views that amount of time seems almost appropriate - it's the paradox embedded within the canyon that is the real surprise. Often unnoticed by the millions of visitors each year, the age of the canyon itself pales in comparison to the age of the rocks within it. Acting upon the canyon's potential for public geoscience education, scientists coordinated the construction of the world's largest geoscience interpretative exhibit titled the Trail of Time.

"Geological time is the key to understanding evolution of the Earth and of life, and all three of these are core scientific ideas," explains Steve Semken, assistant professor in the School of Earth and Space Exploration at Arizona State University and a long-time member of the Trail of Time team. "Our hope is that Trail of Time visitors will walk away with a better understanding of how human time scales relate to geologic time scales."

The concept of a geoscience timeline exhibit based on Grand Canyon geology was first presented to the Grand Canyon National Park in 1995. For nearly 10 years, Semken has worked with founding team members Karl Karlstrom and Laura Crossey, both of the University of New Mexico, and Michael Williams of University of Massachusetts. These scientists, all Grand Canyon researchers for decades, envisioned turning a Grand Canyon hiking trail into a walking timeline that would represent the magnitude of geologic time.

"The sense of awe that the Grand Canyon elicits opens the door to a 'teachable moment' in which visitors are inspired to understand more about the geologic story told by the rocks and vistas," explains Karlstrom.

The Grand Canyon's magnificence and its recognition as one of the most famous geological landscapes in the world sets it apart from other natural features, but its extensive exposure of geological time is also unique. The canyon is considered a very young feature geologically, but what is often overlooked is the fact that the rocks exposed in it are about 2 billion years old. These rocks were buried for millions and millions of years and then within the last 6 million years, the Colorado River cut into them and formed the Grand Canyon.

The Trail of Time is an interpretive exhibit that supports, builds on, and complements other existing Grand Canyon geologic interpretation. Aptly named, the trail was designed to help visitors shift their perspective on time from a personal time scale (years) to historic time scales (tens and hundreds of years), then to archaeological time scales (thousands of years), and finally the geologic time scale of millions of years. It uses the 2-km stretch of existing paved walking trail that edges the South Rim between Yavapai Observation Station, which houses a recently remodeled geology museum, and Grand Canyon Village. Upon completion in 2010 it will be the world's largest interpretive geosciences exhibit.

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 will be 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. A grasp of the magnitude of geologic time is the foundational knowledge needed to construct an understanding of many aspects of our planet from earth science and evolutionary biology to astronomy.

Although the Colorado River did most of the heavy lifting millions of years ago, constructing the Trail of Time was no easy task even with the help of a number of partnering universities such as Arizona State University, the Hebrew University of Jerusalem, Lewis and Clark College, University of Massachusetts, and University of New Mexico.

In addition to the time-intensive labor of inserting the bronze markers, the team faced the unique challenge of creating a project in a national park. It wasn't until the team received funding from the National Science Foundation that the park let the project take hold. Funded by the NSF Informal Science Education Program, a collaborative effort that includes academia, the private sector, and the national park service, this was the first time that any National Park Service site has participated in a project of this type, even though parks are prime locations for informal education.

Informal science education is different than classroom education and ASU graduate student Nievita Bueno Watts, one of the students involved with the project, witnessed this firsthand. Joining Semken, her advisor, Bueno Watts engaged in discussions with exhibitor designers.

"It was the first time I was an integral part of discussions with so many experts, and I was amazed that they really included me and solicited my ideas," says Bueno Watts. "That meeting did more for me as a graduate student than any other single experience I have had thus far."

Though the main theme of the trail is "old rocks, young canyon," other ideas about regional geology will be imparted to visitors such as how canyons are cut, the history behind the different rock layers that are exposed and traditional indigenous knowledge of the Grand Canyon, referred to as ethnogeology.

Time is 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. The Trail of Time also turns out to be a very unique laboratory for geoscience education research to test and learn how people understand time and the Earth.

Two summers ago Semken and his students created a scaled model of the trail at ASU to conduct preliminary research on how visitors navigate it. Bueno Watts was also involved in designing and conducting the cognitive experiment which took place in the halls of the School of Earth and Space Exploration, an academic unit of ASU's College of Liberal Arts and Sciences.

"I also ran a pilot test at Oregon Museum of Science and Industry in Portland. As we learned what worked and what didn't, we adjusted the design of the trail," explains Bueno Watts. "The same mock-up was then used at the Hebrew University in Jerusalem to test how it worked with international populations."

Based on the findings from ongoing formative evaluations, the original version of the exhibit was modified several times. Feedback showed that visitors found it challenging to reconcile the vertical (canyon walls) and horizontal (timeline). To remedy this challenge and further assist visitors in connecting the rocks exposed vertically in the canyon walls to their genesis in geologic time, trailside exhibits consisting of an intriguing specimen from every named rock layer that occurs in the Grand Canyon (30-40 in total) will be mounted at the point in the timeline corresponding to its age.

Geologists often talk of geologic time using units such as eras and periods, for example, Paleozoic or Mesozoic. Though important to geologists, these units don't effectively express the great magnitude of geologic time to the average person.

"Visitors often don't pay attention to when they're going from Cenozoic to Mesozoic to Paleozoic," says Semken. "With this exhibit, though, they'll realize their position on the trail corresponds to, say, 200 million years ago, and 200 meters farther west they'll be at 400 million years ago."

Many educational interventions have been created to address geologic time, but there is nothing comparable in scale or scope to the Trail of Time, according to Semken.

"Though we don't have the funding yet, we would someday like to extend it all the way out to Maricopa point which will be 4.5 km," says Semken. "That would bring people out to the very beginning of the earth, 4.5 billion years."