When one goes to the Grand Canyon, the first impression typically involves how big the geological formation is. The last thing anyone is looking for tends to be a big boulder. The Canyon itself is far more demanding of a visitor’s attention. However, in one particular case, a very massive boulder stood out like an immediate sore thumb.

The boulder itself was no recent creation. The massive, compacted rock was easily dated by millions of years, well before the Grand Canyon ever reached the depths of its meandering caverns today.

For the typical observer, the boulder didn’t really stand out that much. Granted, it was huge by human standards and size, but it wasn’t very distinct from the boulders and ground in the area in terms of color or texture. It originated from a nearby cliff on the Bright Angel Trail, essentially coming loose due to gravity and eventually falling lower until it stopped at its current location. Visitors and hikers passed by this boulder for years without any notice or care.

Allan Krill had been a trained geologist for years, studying the intricacies of rocks, soil, water, and the rest of the earth’s formations.

In the geology world, it’s hard to be the discoverer of something new, much less novel. So much of geology has been documented, surveyed, tracked, studied, and photographed that anything someone thinks they “found” turns out to be already thoroughly examined in one research paper or another.

The boulder itself was not the prize. Instead, what was preserved in the stone of the boulder was amazing and worth the world’s attention. Krill now just had to get others to confirm his suspicion was correct. If he was right, the find easily dated back deep into the era of the dinosaurs at least.

As so often happens, Krill’s discovery took a number of coincidences and circumstances to happen first for his discovery to even be visible by the geologist. The sequence of crumbling, cracking, gravity and falling in just the right exposed way made the difference in making the boulder’s secret see the light of day for Krill to “discover” it.

The above said, the Grand Canyon has long been a repository of secrets. From inaccessible caves visible but not reachable for years. Yet, as erosion cuts through the layers like a hot knife through cheese, the natural wonder is stuffed with geological finds.

Back then, the world was amazingly different. Even the continents themselves were in different positions globally. What used to be clearly lush, heavy vegetation-covered land disappeared over time, and the Arizona desert and arid conditions replaced the climate in the region to what we know today.

Again, for a big rock, 2 billion years is a typical run in the park. Most of the earth’s exposed rock, mountains and formations have been around for thousands, millions, or billions of years.

The particular area of the Grand Canyon bears all the vicious signs of intense geological activity. From significant pressure under weight to high temperatures to volcanic and metamorphic activity, the stones and rocks in the area were brutally melded and forged.

As every sedimentary layer was applied with time, it also became what geologists study intently as their version of history books. Not only the type of minerals and what was buried in them tell stories, but how the sedimentary layer was created and deposited makes a huge difference as well.

Long after much of the above activity happened, the Cretaceous Period arrived. It was about this time that many experts agree the Grand Canyon likely started being formed, at least in terms of something becoming the gap in the Earth we know today. At that time it didn’t cover the 130,000 square miles the Canyon encompasses today.

When people look at the Grand Canyon today, they can’t imagine it being a small, little creek meandering through and off a plateau. Yet, today, the geological formation covers four states in its size, claiming territory in the four corners of Arizona, Colorado, New Mexico, and Utah.

The particular change agent of water came in the form of rainwater and ice as the same froze during cold periods. The Rocky Mountains became the watershed, generating much of the moisture and its build up. At first, the condensation factors had very little effect. However, with millennia to work with, water and time can do amazing things.

Erosion also has an abrasive effect. As water tears apart rock, it breaks it down, turning rock into boulders and boulders into stones and pebbles, all of which bang against the remaining rock and create multiple points of impact, some with significant force. Damage cascades into more damage and that in turn creates more erosion.

In modern times, the Grand Canyon enjoys National Park and Monument protection. Internationally, it is easily within the Seven Natural Wonders of the World. Even more interesting, the Canyon is not staying the same. While its current form was realized about 1.2 million years in the past, minuscule changes continue to occur that add up over time.

Interestingly, humans and the Canyon have a long history as well. Ancient peoples frequented the Canyon on a regular basis, easily noting its significance in the landscape by then, even though humanity was still a blip in the geological history range.

The Grand Canyon region was first designated a forest reserve in 1919, an early federal government predecessor to what would later become a National Park designation.

Tourists aren’t the only ones visiting though; researchers spend an extensive amount of time in the Canyon on a regular basis. Studies and research have been on a steady diet in the area since before its designation, dating back to 1858.

The Grand Canyon easily gains recognition in photographs and films for some of its more famous locations. Created by an assortment of water movements, wind, arid conditions, and erosion, a number of locations within the National Park have become go-to spots for tourists from around the world.

In 2014, researchers pushed out an academic paper which said that the majority view of how the Colorado River formed the Canyon seemed to be incorrect. Instead, the River’s behavior had moved in a very different way. For the average person, these sorts of discussions seem like splitting hairs on insignificant what-ifs, but in the geology world it’s akin to someone proposing to rewrite the Bible or the Koran.

In the meantime, the River continues to keep doing its job cutting into the Canyon. That action is, unfortunately, now also being destructive to the evidence of ancient history. Erosion is not delicate like a scalpel; it tears into all forms of geology, even those that have been valued by research.

Fossils are mineral leftovers from organic life. They can be created either by animals or plants. Under the right circumstances, the organic material gets preserved and replaced by minerals.

That was the case with a 2019 Grand Canyon discovery announced by the National Park Service involving the footprints of a tetrapod, a four-legged creature older than ordinary dinosaurs.

Regardless of the amount of research, as Krill’s find would prove, getting out in the field and walking the ground still tends to be the best way to understand the geology of the Grand Canyon. And, despite how much research has been collected, discoveries still pop up.

The Trail starts near the Grand Canyon Village, the primary tourist starting point for exploring the Grand Canyon. Then, the trail moves into the Canyon itself, while running parallel to the edge, lowering in elevation some 4,000 feet for eight miles.

The out of place boulder was easy enough to spot, making it a natural attractant to an observer on the trail. However, for Krill, there was a lot more going on, and he wanted a closer look at the boulder’s story. His eye caught an aberration in the stone’s surface that didn’t look right and definitely didn’t look geological.

For geologists, the Manakacha Formation is a geology playground. Originally mud and soft Earth in its original form millions of years ago, the mudstone and limestone now tends to be a treasure trove of fossils and captured material preserved in the ancient mud.

What caught Krill’s eye on the boulder’s surface, however, was a marking that looked like a footprint. And, there was more than one. In fact, his discovery found a pattern of footprints fossilized in the boulder. Krill took a number of photographs and then sent one of them to a paleontologist for confirmation.

While Krill’s eye had made the original discovery, the depth of the finding took another year or two to be fully understood. Paleontologists who studied the boulder and formation intently detailed their findings in the fall of 2020, again crediting Krill with a major find. As it turned out, the footprints involved were far older than previous conclusions.

Scientists concluded that, while they couldn’t identify the creature, it was definitely reptilian and living in an arid location.

For today’s reader, it’s a bit hard to understand how dinosaurs long depicted being in jungles ended up in the desert arid regions of Arizona. Part of the perspective problem comes from the fact that today we think of the world as it is, not as it was.

It’s likely that instead of eroding flat, the tracks were subsequently covered up by water and more mud, which caked and preserved their form.

A lot of the academic debate continues to rage back and forth whether the reptiles tracked through the area are the same time or were separate tracks. Were there two separate reptiles or only one?

However, all accounts do agree that there are two distinct sets of footprint tracks preserved in the boulder. And the mechanics of the walk pressure, impression, gait, and depth of the print say a lot about the type of creature that caused it.

Yet, despite all the academic research published since Krill’s discovery, the boulder and its secret are still being hotly debated. Much of the disagreement centers around exactly what kind of reptile made the tracks, how they were made, and what one should infer from their shape and presence.

As for the rest of the world, those hiking down the Bright Angel Trail just see a big boulder that stands out as a visible shop to stop and catch one’s breath.

However, for the scientists, the prints might as well have a blazing neon sign posted over them, enticing all to come visit and check it out. The boulder is truly that exciting of a find and geologists love to visit with its history.

So, if the story above appeals to you, and you want to train your eye to find things as you go hiking the way scientists look at the world, the first step is to study up on your geology or go to school to become a geologist. Krill’s observation involved being at the right place at the right time, but to the untrained eye this discovery would’ve gone unnoticed.