About eight miles west of Bluff, UT, US-163 cuts through a stunning monocline called Comb Ridge. This fold in the earth’s crust, developing 65 million years ago, is similar to folds we’ve seen and especially the Waterpocket Fold in Capitol Reef National Park. How do these rock folds develop? It is all about tectonic plates. What kind of plates? Let’s go . . .
I am absolutely no geology expert. I try to find simpler explanations for the amazing rock formations we see in the West. However, I end up needing a dictionary to look up many words in the so-called simple explanations. So bear with me and let’s go.
Tectonic plates are huge pieces of the earth’s lithosphere (earth’s crust and upper mantle). There are seven major and ten minor plates on earth. The seven major plates cover about 95% of the earth. They move, often due to the molten lava at earth’s center. It is the plates’ movements that create mountains and ridges such as Comb Ridge.
Comb Ridge formed when one tectonic plate slid under another pushing rocks up into a fold. The fold’s west side (first picture above) was the high side of the fold, eroding over millennia. The east side of the fold (below) is gently sloping ground (rock and soils).
Comb Ridge is a monocline, a fold that dips down in only one direction. Of course the creation of a monocline is much more complicated, but thanks to Utah Geological Survey for this helpful picture.
A: the fold created by the sliding, overlapping tectonic plates, in this case the North American and Pacific Plates.
B: the higher western side of the fold eroded over time leaving shear cliffs–the more flat eastern side changes very little.
Speaking of time, the entire process took at least 40 million years. We won’t talk of all the different types of rock, but some are softer and erode faster. That’s what makes the amazing rock formations across southern Utah. Now let’s zero in on Comb Ridge.
This ridge is about 80 miles long in a north/south direction. Beginning near Blanding, Utah, about 25 miles north of our home base in Bluff, and ending near Kayenta, Arizona, about 25 miles south of the northern border of Arizona. It is called Comb Ridge due to the jagged appearance of the ridge’s top, similar to a rooster’s comb.
US-163 takes us through the Comb. I parked off the edge of the road for these pictures. There are places where this is illegal, not here–hooray! Looking back to the slice in the Comb that is US-163.
Looking north along the Comb. It is lovely sun and blue sky here, as you see in most pictures. Looking north? Rain. Although it looks like the road ends down below, it actually makes a sharp left to continue traveling west.
A few miles away, we can see more clearly the sharp turn through the Comb.
Comb Ridge from top to bottom: we have the ridge itself, then sliding rockfall, US-163, sliding rockfall, small Utah Junipers and a variety of grasses. Then bright green Cottonwoods along Comb Ridge Wash. A wash? It is the place where seasonal streams and flash floods flow to the San Juan River, a few miles to the south. Washes are all over the west, but are usually sandy channels until the rains fall, like the common summer thunderstorms. Lastly we are standing on thick, hard, white Navajo Sandstone with Utah Junipers, Serviceberry, some grasses, and bright sun. Better go get some sunscreen.
The high, pointed rock mid picture is the highest point on Comb Ridge, rising over 700 feet from the level ground below.
On either side of the Comb are dirt roads, approximately 20 miles long and linked to major roads, US-163 south and UT-95 north. As with any dirt roads, beware of incoming storms. Never travel them during or after rain. The sand and dirt can become like glue then drying like cement. All those clouds north? Not doing dirt roads today. Dang!
The eastern road is Butler Wash Road. Starting from the south off US-163, you will find trails to canyons, ruins, and superb petroglyphs. It may offer great adventures, but friends have warned me the road becomes tough to travel, even dangerous, the further north you go. If you come to explore, use caution and be willing to turn back to the highway. Toughing it out is not always the best choice. Towing is very expensive.
The west road is Comb Ridge Road. There are free camping areas along the road (no campground services), a few small ponds and a fishing access trail to Fish Creek. Not to mention the stunning view of the western side of Comb Ridge. This would have been my choice. Maybe next trip.
Until next time my friend . . .
