nazSTUFF - Grand Canyon Elementary Geology

Rascal Inquires, " If You Are Not Concerned About the Future, Then You Haven't Been Paying Attention." This, then is our advertising campaign, to contribute to your well being.

Grand Canyon Geology

"Northern Arizona Experience" - CLICK ON ANY IMAGE for more information and design details. Make changes.

The Grand Canyon in Arizona is known as a living laboratory displaying the oldest rock formations on earth. Science, art and adventure come together in this magnificant place. This page presents some elementary information about Grand Canyon geology. JVroom

This simple animation provides you with a visualization of how the Colorado River has "downcut" into the rock layers of the Grand Canyon. This is highly simplified as it doesn't include side canyon debree flow and the widening of the canyon over time.

How long it took for erosional forces, and some earthquakes, to carve the Grand Canyon is debated by geologists. I've read of estimates between 6 and 8 million years, which is very recent by comparison.

This "chunk" of the canyon that we have isolated in this photo is a prime example of the layers we want to learn more about, for it contains within itself all of the visible paleozoic geological layers that you can see from the canyon rim down to just above the river.

Names of the Depositional Layers in Grand Canyon

Here we have peeled back the surface texture of this "best section" of the canyon to reveal something of the composition of each layer. Each general layer is labeled in this illustration so that you can learn the names.

Interpretive note:

You'll notice that the internal color of the various rocks is different from the surface color you see. This is particularly true of the layer named Redwall Limestone. This is a large vertical cliff formation that is easy to identify throughout the canyon. This huge block is primarily limestone that was formed at the bottom of an ancient ocean. Its true color is primarily shades of gray and it is filled with ocean fossils. But because it is located below the red shales above, it is constantly being stained by the erosion of these colors as they wash down over it, creating a red wall.

In the material above we looked at the paleozoic layers of the canyon. Here is a photo, taken further east of the previous photo, that reveals an entirely separate group of depositional layers that are deeper in the canyon.

Grand Canyon Supergroup

These layers are found below the Tapeats Sandstone and are all tilted about twelve degrees toward the northeast. These layers are referred to as the Grand Canyon Supergroup. According to geologists these rocks are over one billion years old.

Ancient Mountain Building

Here we have focused again on a section of the photo to emphasize the tilted layers. The red line indicates the tilt angle of these layers toward the northeast. The blue line indicates the place where the older supergroup rocks meet the younger layers we have already described. This line is called the Great Unconformity. It is an "unconformity" because much geologic material is missing. In fact, in this area of the Grand Canyon over 500 million years of information is missing!

Identifying Southwest Land Forms

Observing land forms in and around the Grand Canyon is easy. There are so many and they are everywhere. Remember, the names of each specific shape is really the name of one "step" in an overall process. Land is built and eroded in huge cycles of time, so huge that we cannot observe the process. What we see is a snapshot of where things are now during our own brief time of observation.

Here is a simplified illustration of typical land forms in our region.

Can you identify any of them before looking at the labeled version below?

Most land form shapes are the result of erosion in one form or another. The largest in our area is the plateau. If you look at a map of the area you will see many plateaus identified, such as the Kaibab Plateau and the Walhalla Plateau. Next in size are the many Mesas, followed by Buttes, Pinnacles and Hoodoos. Each of these in a previous time was part of the larger version before it. In other words, a Hoodoo was once a Pinnacle. A Pinnacle was once a Butte, and so forth. It's all part of a process of erosion. In time a Hoodoo falls down and becomes a clump of rock boulders.

In this way land "retreats" away from the source of its erosion. Hence, the Grand Canyon is always becoming a little wider all the time.

More Info on our BLOG