You don’t need to know a thing about geology to hike in the Grand Canyon. Just find a trailhead and head on down and, hopefully, come back up at the end of the day. But any sensible Grand Canyon hiker takes precautions. Do you know your limits? Do you have enough water, or know where you will get it? Are you sensible enough to not stray far from the rim on a very hot summer day without really knowing what you are doing?
Knowing at least a bit about the geology of the Grand Canyon is another sensible precaution. Most of the rock formations in the Grand Canyon follow a regular pattern. Each formation has its own distinctive look and feel, and experienced Grand Canyon hikers can look around at the rocks surrounding them just about anywhere in the canyon, and know just what formation they are in. And if you know what formation you are in, you can have a pretty good idea of just how long it will take you to go up or down to get to wherever you are going. And with that knowledge you can properly pace your day, and safely enjoy the splendors that surround you as you hike.
In these geology pages I’ll present some scientific geological information, but not a lot. My focus will be to give you the information you need as a hiker about each formation – the appearance of the formation, and what you can expect trails to do when they pass through the formation. I encourage you to visit the panoramas that each formation article links to. The best way to learn formations is to hike canyon trails and watch the rocks attentively, but exploring the panoramas here can give you a good head start.
As you hike down Grand Canyon trails from the rim and penetrate the depths, you will encounter a series of barriers. The first major barrier, the Coconino Sandstone, comes about 15 minutes to a half hour into your hike. In most places it forms high, impenetrable cliffs, but there are breaks that trails pass through. When you get to the top of the Coconino you can say to yourself ‘well, if I keep going, I know it will take me 30 to 60 minutes to get back to the rim from here’, using the rule of thumb that you double your time going down to estimate the time required to go back up.
The second major barrier, the Redwall Limestone, is generally about an hour to and hour and a half down from the rim. The top of the Redwall is about half way down from the rim to the river. When you descend past the Redwall cliffs, the highest and most imposing in the canyon, you truly enter the desert, with all that that entails. Brutal heat in the summer, and water and shade scarce if not non-existent. If you venture below the Redwall, you have to be prepared and know what you are doing.
The third major barrier, the Tapeats Sandstone, generally is about two to three hours down from the rim, but depending on which trail you are on, it may take you much longer to get there. The Tapeats forms the rim of the inner canyon, which has the Colorado River flowing at its bottom. You can’t see much if any of the inner canyon from most places on the rim, but if you are standing on the rim of the inner canyon in the Tapeats, with glimpses of the river below you and the towering towers and buttes of the canyon above you, the view is spectacular. And you will know that you still have another hour or so ahead of you to reach the Colorado River.The first nine major formations descending from the rim of the Grand Canyon are neatly stacked and are always in the same order. Here, in this picture taken along the South Kaibab Trail, we can clearly see all nine, starting with the Kaibab Limestone of the rim and proceeding on down to the Tapeats. There is a page with detailed information for each of these formations that you can click on in the menu on the left side of this page (or at the top if you are viewing this page on a mobile device with a small screen).
These nine layers were laid down as sedimentary formations one on top of another, with some time gaps in the record, over a period of over 250 million years. The oldest formation on the bottom, the Tapeats Sandstone, was deposited about 525 million years ago, and the youngest, the Kaibab Limestone on top, was formed about 270 million years ago. That leaves a very long time between the formation of the Kaibab and today. There are, however, another 13 formations that are stacked on top of these nine. They have all been eroded away in the area of the Grand Canyon, but you can see them appear one after another as you head north beyond the Grand Canyon into southern Utah, with the highest and youngest formation, the Claron Formation, forming the fantastic spires and hoodoos you see at the top of Bryce Canyon National Park. All of theses 9 + 13 = 22 formations together are called the Grand Staircase.But at the rim of the inner canyon at the top of the Tapeats Sandstone, you still have up to 1500 feet down and many formations between you and the Colorado River. Between the Tapeats Sandstone and all the formations below it there is a huge gap in time called the Great Unconformity. Here we are standing on the Tapeats rim, looking across the river at the inner canyon. Below the Tapeats you see a swirling mass of black and pink rocks known as the Vishnu Complex, also commonly called the Vishnu Basement Rocks. The Vishnu is over a billion years older than the Tapeats. There is another set of formations, called the Grand Canyon Supergroup, that you find in the inner canyon. Here we see the bottom three of the supergroup formations, the Bass Formation, the Hakatai Shale, and the Shinumo Quartzite, sitting on top of the Vishnu Complex, but as always, along with the Vishnu, underneath the top nine formations and the Great Unconformity. Notice how the supergroup formations are tilting down to the river. They are flatly stacked one above another, but almost always are tilted as a group to some degree from the relatively flat level of the Tapeats and the Great Unconformity.
In most places in the inner canyon, you see only the Vishnu beneath the Great Unconformity. But in places within the inner canyon, scattered here and there throughout the park, one or more of the supergroup formations will appear. Geologists that have attempted to reconstruct earth’s history of continental drift (plate tectonics) believe that the Grand Canyon area was part of a supercontinent named Rodinia that broke apart some 600 million years ago. Scattered, giant blocks of rock, called grabens, dropped down into the gaps that formed as Rodinia was pulled apart. In the Grand Canyon, the supergroup formations, which were deposited on top of the Vishnu, were lowered down within these grabens into the places where we see them today.
There are a total of nine formations within the Grand Canyon Supergroup spanning a period of 500 million years, from 700 million to 1.2 billion years ago. The bottom four, the Bass Formation, the Hakatai Shale, the Shinumo Quartzite, and the Dox Formation, are the only ones that you will encounter unless you head way back into very remote portions of the canyon, and they are the ones I will cover in these pages. Like the top nine formations they always appear in the same order, and each has its own distinctive look and feel.