The New Trail of Time at Grand Canyon National Park - A Review
Wayne Ranney

Incredible as it may sound, it was not that long ago that geology was nowhere to be found in Grand Canyon National Park. Of course, this is not to say that the canyon itself lacked any geology, but rather refers to the ironic fact that topics concerning geology were mostly absent in the displays and interpretive signs found within the park. Visitors rarely were made aware of the canyon's connection to geology or of its world-class significance as a premier geologic wonder. However, with the May, 2007 rededication of the Yavapai Observation Station as a superb regional geology museum and the October, 2010 opening of the Trail of Time, geologic interpretation has now taken center stage at Grand Canyon National Park.

The gathering crowd during the Trail of Time dedication ceremony.

Billed by its creators as "the world's largest geoscience exhibition at one of earth's grandest geologic landscapes," the Trail of Time (TOT) interprets the geology of Grand Canyon's spectacular views and its largely inaccessible rocks. The trail leads visitors towards key geologic concepts that can be read in the rocks of the canyon and serves to help people contemplate and more fully appreciate the enormity of geology and the larger meaning of geologic thought. One of the recurrent themes presented on the trail is that of "deep time" something that the Grand Canyon has in spades. I was honored to be a participant and presenter at a three-day symposium held during the dedication of the TOT, October 13 to 15, 2010. I have already and will continue to use this marvelous education tool in the many informal learning opportunities that I am so privileged to conduct at the canyon. The TOT is the brainchild of Dr. Karl Karlstrom and Dr. Laura Crossey of the University of New Mexico and a host of other professionals, who envisioned an exhibit that could help park visitors learn about and interact with the canyon's stupendous geologic heritage. Initially conceived in 1995, the trail went through numerous iterations before a grant from the National Science Foundation came in at the tune of $2.4 million. Working closely with the parks interpretive staff and utilizing other cognitive and evaluative resources, the group sought to develop an educational geoscience exhibit that would be accessible to a wide-range of learning capabilities. The result is striking and visitors can't help but partake in the stunning display as they walk the popular Rim Trail between the El Tovar Hotel and the Yavapai Observation Station.

The 2 km long timeline represents 2,000 million years of earth history with each million-year time segment marked at one-meter intervals with small brass rings embedded in the asphalt footpath. Such a layout means that one long stride represents one million years of time. At each 10-million year interval, a 4-inch diameter brass medallion displays the precise number of years shown along the trail. At the trails west end near the El Tovar Hotel is the 2,000 million year brass medallion, while a 0 million year medallion its located at the trails east end near the Yavapai Observation Station. Along its 2 km length visitors will find four beautiful stone portals, thirteen interpretive signs, and thirty-three concrete pedestals, with formation names and ages etched upon them, and topped with actual rock specimens from the canyon's inaccessible depths. Visitors now have a way to see and touch Grand Canyon rocks. The four portals are constructed at key junctures in the trail, are superbly rendered and are perhaps the exhibits' most stunning attraction. They are composed of actual rock specimens that have been proportionally measured, cut, polished, and placed within each 7-foot tall monument, presenting a quite recognizable vertical profile of the canyon. At their base, each portal contains the Precambrian crystalline rocks cut into a v-shape representing Grand Canyon's Inner Gorge. Slabs of layered Supergroup rocks are then placed at an angle on one side, all of which are covered with flat slabs of Paleozoic caprocks on top. The portals are both scientifically enlightening and wonderfully artistic, and many visitors already have been seen having their picture taken next to one of these scaled forms of the Grand Canyon. At each portal a semi-circular stone "patio" is laid with flat, time appropriate rocks that allow groups of people to admire the portals while standing off to the side of the trail.

The thirteen wayside signs focus on diverse topics such as the Great Unconformity, the ancient environments that created the rocks, and the canyon's carving in the last six million years. As visitors approach the east end of the trail, the wayside signs cover subjects covering recent climate change, Quaternary volcanism, and the relatively recent human history in Grand Canyon. In eight instances the wayside signs are complemented with viewing tubes placed adjacent to the signs and serve to direct the visitor's gaze towards key geologic features that can be seen in the canyon. These viewing tubes continue a long and time honored tradition at Grand Canyon National Park and in each instance a separate tube is provided for small children and taller adults. The viewing tubes help connect visitors with one of the more challenging aspects in the educational design of the trail – how to link a horizontal timeline with the vertical record of rocks that is to be seen in the canyon.

Another fascinating feature of the TOT is the way time itself is metrically expanded for the last one million years. Near its eastern terminus, the "Million Year Trail" moves visitors through a series of changing time-to-distance scales, helping them to shift their thinking from the thousands and hundreds of millions of years they have been seeing to a more human centered time perspective - millennia, centuries, decades, and finally individual years. The "Million Year Trail" begins with an inset brass line that runs diagonally across the trail to highlight the change in scale. Meter-spaced medallions are then labeled for each 100,000 years - 900,000 years, 800,000 years, and so on. At the medallion labeled 200,000 years, time is scaled down once again to 10,000-year intervals - 190,000 years, 180,000 years, etc. Each interval is still one meter in length but time is continually "stretched" a few times in this way along the trail. The last 60 meters have a medallion for each year – 60 years, 59 years, 58 years, etc.

Brass medallion marking the 1600 Million Year point on the Trail of Time.

I love the TOT and found only a few things I might have done differently. A certain Proterozoic bias is apparent in some of the rock units chosen for display. Volumetrically limited members of some Supergroup units share equal visual representation as the more widespread and easily observed Paleozoic rock formations. And along a one-quarter length of the trail that has no signage at all, I might have added one additional sign between the 1,400 and 1,200 million-year medallion telling people that the Vishnu highlands were being leveled by erosion at this time. Perhaps in this way the exhibit could help show visitors how geologic reasoning works to interpret those times where no rock record exists. Lastly, I wish there would have been medallions for individual years up to 100 years instead of only 60 years. Practically everyone then who walked the trail could stand on "their year."

The trail's originators seem keen to adapt some aspects of the exhibit's design as ongoing evaluations warrant it. And any minor quibbles quickly fade away in light of the exhibits' overall necessity and desirability at Grand Canyon National Park. Our science is becoming increasingly relevant to a society that scratches every hidden corner of the planet for energy resources while at the same time (ironically) strives to understand climate change. As geologists, we can and should be major contributors in policy discussions and decisions. But regrettably, we as a community until very recently have been so bound up in our endless enthusiasm for "all things earth" that we have forgotten the masses of citizens who so far have shown little interest in or knowledge about what we do or how the geo-system works. This exhibit is a welcome, innovative, and needed addition in addressing these shortcomings. And for those of us who love to share the deeper meanings that the Grand Canyon can provide, the Trail of Time is a powerful tool that can direct ordinary people's thinking towards things geologic. This is only right and natural at a place like Grand Canyon - a place that changes lives everyday. This exhibit will facilitate that change for untold numbers of future visitors and many of them just might get turned on to geology without a geologist in sight!

The Trail of Time was conceived, designed, and installed by Karl Karlstrom, Laura Crossey, Michael Williams, Steven Semken, Judy Hellmich-Bryan, and Ryan Crow. Financial support came from the National Science Foundation and all work and support was provided by Grand Canyon National Park. You can learn more about the trail at: and Journal of Geoscience Education, v. 56, n. 4, Sept., 2008 p. 354-361.

Suggested reading:
Journal of Geoscience Education, v. 56, n. 4, Sept., 2008 p. 354-361

Wayne Ranney, geologist, author, and river and trail guide

Flagstaff, AZ

Author of:
Sedona Through Time, Ancient Landscapes and Carving Grand Canyon

Arizona Geology is published by the Arizona Geological Survey. | © The Arizona Geological Survey, 2011. All Rights Reserved.
Editor: Michael Conway