Walk Through Time, in Blacktail Canyon

I was in Blacktail Canyon, 120 miles below Lee’s Ferry in Grand Canyon when I first heard the “Walk Through Time”. I was on a river trip with legendary senior guide Matt Herman, as he put things into perspective for our guests. Blacktail Canyon is an extraordinary place to witness the depth of geologic time, along with the processes that create these most impressive canyons. Matt started at a big rock in the channel, not too far from the mouth, and started pacing out each step of Earth’s development from the beginning to now. The most impressing thing was walking through the rock layers of the Grand and ending with human existence as just a infinitesimal part of Earth’s journey. I told Walker Mackay about the “Walk Through Time”, and it reminded him of a book he read by William H. Calvin called “The River That Flows Uphill”. There, I found what sounded similar to what Matt had presented to us that day. Here is a summery;

Very few places exposed on Earth’s crust reveal the depth of the geologic record revealed in Grand Canyon. If you were to pace out Earth’s existence in its entirety (with each step representing 100 million years) it would take you 46 steps to bring us to today. It would take 6 steps to represent the time it took for the atmosphere to accumulate and 3 more steps for the surface to cool enough for the oldest rocks to form from the original crust. At 11 steps from our starting point, the very first cells develop. Over the next 5 steps, stromatolites emerge, and the foundation of the continents formed through lava flows. Now at 16 steps, the crust is able to support deposition of sedimentary and igneous flows and land mass grows while mountain building begins. Bacteria evolves to photosynthesize at 21 steps, and 3 steps later the Earth enters the first ice age. Two steps further the ice age ends and fungi shows up, and 2 steps again represents the accumulation of oxygen in the atmosphere and we reach an important place on our timeline.

Two thirds of the way into our journey and the schist which is seen in the walls of the Grand Canyon first forms. (This is the black rock at the bottom of Blacktail Canyon, and which through, at river level, we ran the Inner Gorge). In 5 more steps the supercell evolves and sedimentary layers of rock get bucked up to form the Appalachian Mountains. Boom! 36 steps in and our world gets rocked upside down. Sex is discovered and cells are able to replicate. Colonies of cells explode and life takes off. 3 steps to jellyfish. 1 more for the Cambrian Explosion. In a single step, vertebrates. (And this is where the Tapeats Sea bordered this area, and deposited the sands of this stone now above us, also called Tapeats.) Another step, land plants and spiders. Half a step for reptiles and a hiccup for the Permian Extinction. Then birds emerge and dinosaurs rule. At 45 steps in (while the leg is swinging into the final step), dinosaurs go extinct, mammals take over, apes evolve and ice ages oscillate. When that foot plants and comes to a stop, human existence would be represented by the portion of the toe nail you could clip off. Ancient civilizations. John Wesley Powell. The Bureau of Reclamation. Edward Abbey. Hayuke..


Matt’s presentation was on point, and people were impressed. By this time on our trip, we had gone nearly half-way through the canyon. We had watched as the walls rose up, layer after layer and oscillated up and down as the river cut through. Seeing the rock go from several hundred million years old and jumping to almost 2 billion years old as it does in Blacktail makes it hard to put into perspective how this relates to our personal sense of time. The first few day of a river trip seem to go in slow motion. Then, something strange happens. The days just fly by and what happened yesterday seems to blend into what happened the day before. To fully grasp what one is feeling and experiencing on a river trip is really difficult to explain in words. To understand how our lives compare to the deep geological time represented here is nearly as difficult as understanding our place in the cosmos. Very few places but the Colorado River can provide this perspective. Beyond the rapids, the waterfalls and beaches, sometimes it is the intangible discoveries that make a river trip a life-changing event.


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