Newswise — The desert-hued rock layers that make up the walls of the Grand Canyon represent 2 billion years of Earth history, exposed as the Colorado River eroded the rocks of the Colorado Plateau. Now that history is being brought to life by a team of scientists including Mike Williams of the University of Massachusetts Amherst, who are creating the world's largest geosciences exhibit on the canyon's southern rim.
The 2.8 mile "Trail of Time" will use existing walking paths between the Yavapai Observation Station and Grand Canyon Village and will be handicapped accessible. Telescopes for inspecting layers in the Canyon, rock samples and explanatory waysides will inform visitors of the areas geologic past. Construction on the trail will be launched in October 2007.
"Close to 5 million people visit the Grand Canyon every year, but only a tiny fraction walk into the canyon," says Williams. "The "Trail of Time" will allow us to teach these visitors about geology and geologic time."
Bronze markers will be placed in the trail every meter, each marker representing 1 million years of Earth history. The first six markers cover the carving of the canyon by the Colorado River.
"This is an important concept," says Williams. "The Grand Canyon is less than 6 million years old, but the river cut through much older rocks that were uplifted."
This uplift, which formed the Rocky Mountains and raised rocks originally formed at sea level to an elevation one to two kilometers above sea level, allowed the river to continue eroding downward. Waysides along the trail will include telescopes to focus on the corresponding rock layer in the canyon as a way to connect the timeline to the geology. Visitors will be given a walking guide and be able to touch rock samples taken from the canyon. "Right now, the entire trail is lined with the limestone that makes up the rim," says Williams. "This will be replaced in some areas with actual samples of canyon rocks for visitors to study." Samples will be gathered by raft from loose blocks carried downriver or lifted out of the canyon by helicopter.
The entire history exposed in the canyon walls will be presented in the waysides. "The area started as a series of volcanic islands similar to Indonesia that was added to the North American continent," says Williams. "These rocks are represented by the Vishnu Schist that lies at the base of the canyon," he says.
The geology provides evidence that the area behaved as a relatively stable continent. Sedimentary rocks were deposited in deep basins or rift valleys, and then the area became a coastline with shallow warm seas that advanced and retreated, depositing layers of limestone, shale and sandstone. Many of the rock layers are rich with fossils. "For a time, the area was even a desert," says Williams, "so the rock record gives us information about climate change."
The rocks began to rise from sea level about 60 million years ago during the Laramide Orogeny that formed the Rocky Mountains, with the final step being the carving of the canyon in the last 6 million years by the Colorado River watershed. A major goal of the project is to teach people the concept of geologic time. A time accelerator is located before the main trail, with the first markers placed every meter representing one year. "Everyone can stand on markers that represent events they can relate to, like their birthday or the Civil War," says Williams. Gradually, every marker will represent a larger time interval, allowing visitors to transition from personal time scales to the vastness of geologic time.
The "Trail of Time" project began at a research meeting in 1995. Rangers and scientists were frustrated by the lack of geologic information available to Grand Canyon visitors. "We got the idea to make a new type of exhibit that takes advantage of the canyon as a display," says Williams, who will travel to Arizona in October for the installation. Rangers from a number of national parks have participated in workshops and discussions. It is hoped that the "Trail of Time" will be a prototype that leads to a series of "Trail of Time" exhibits at other parks. "Most people visit multiple parks," says Williams. "Why not let these interpretive materials cross park boundaries?" Several other components have been designed to increase education at the canyon. The Yavapai Museum, a former bookstore, has recently been restored as a geology museum. An adjacent amphitheater will be used to present lectures on geology and current research. A Web-based "Virtual Trail of Time" will allow visitors to preview the exhibit before traveling and answer follow-up questions after they leave. Funding for the "Trail of Time" was provided by a $2 million dollar grant from the Informal Science Education Program of the National Science Foundation. Major partners in the project include Grand Canyon National Park, the NSF, the University of New Mexico and Arizona State University. UMass Amherst is one of three academic institutions participating in the project. Completion of the trail is scheduled for 2009.
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