Let’s take a walk to the largest arch not only in Arches National Park, but North American. It has a light opening of 306 feet, 4th largest in the world. Found in the Devils Garden area of the park, it is a 1.9 mile round trip hike that promises to be stunning. It’s a very windy day so hold onto your hat, grab your water, and let’s go!
The hike starts through a canyon. The geology here is fascinating. If you are interested, see what Park Service geologists have to say. Although it took millions of years to form what we see today, it is now mostly water, both rain and snow, that carve the landscape sending eroded rocks through canyons and washes to the nearby Colorado River. Whoa, that’s a tight turn up ahead.
Notice the darker red and black streaks down the sandstone walls? We will see it all over Utah’s canyons, not to mention in Wyoming and Colorado. It is Desert Varnish, a thin red-to-black coating of minerals, but mostly manganese (Mn) and iron (Fe). Varnish is often caused by atmospheric dust and surface runoff, but wind plays no part in the coating. Desert varnish was often used by American Indians to carve their petroglyphs.
Why are there different colors? Glad you asked 😉 . It is all about the relative amount of manganese and iron. Manganese-rich varnishes are black and iron-rich varnishes are red or orange. Varnishes with similar amounts of manganese and iron are some shade of brown.
It is surprising that all over red-rock country these varnishes, especially black, have been forming for thousands of years. Somehow I expected them to be younger, after all it is “just” a varnish. Geology is amazing.
Most of the formations along this trail have no names. The geologic time line for many of Arch’s formations is the Jurassic period, between 146 to 200 million years ago. Today we see primarily four types of rock which I’ll let you explore on your own if interested. Succinctly (very) the top light-colored rock and lower layers is Curtis Formation (Moab Member). The rock being carved into the formations is Entrada Sandstone (Slick Rock Member); the base of most of the formations is the Carmel Formation (Dewey Bridge Member) with the entire formation sitting on Navajo Sandstone. Other formations outside the park have a differing structure–geology can get confusing but relatively simple in Arches.
See the varnish?
The geology may be a struggle, but the evergreens are easy. These are Utah Junipers. Their secret to surviving in harsh canyon and desert conditions? “A massive underground root system which can account for two-thirds of a tree’s total mass. A juniper’s tap root can penetrate 25 feet straight down in search of water. It can also send out lateral roots 100 feet or more from the tree.” Thank you Canyonlands Park Service for the wonderful information about the “Indomitable Juniper“.
The warnings are at every trailhead in Arches–watch for falling rocks! Erosion never ends and arches continue to fall. Consider Wall Arch and learn about falling arches and other formations. It is only a matter of time for each and every formation we encounter to fall. This rock looks like it could crash down at any moment, but may be more tightly connected than we know. What about Balanced Rock–anytime soon?
Desert varnish adding beauty to the rock walls.
Hoodoo in the making?
A clear view east to all the canyons formed by various creeks heading south to join the Colorado River.
We are getting close to Landscape Arch, heading down a set of wood steps built into the steep hillside. From here we can see Partition Arch. A steep hike up we will not do today (at this point in my life, maybe never–this getting old is not for sissies!).
Ah, here we are! Over the years sections of the arch have fallen, most recently in September 1991. After that fall, the Park Service closed the trail to stand under the arch. The narrowest section of the arch is only six feet in diameter. No telling when this arch will crash, but it will. Erosion never ends, but we certainly can enjoy it now! Notice the varnish.
A closer look at Partition Arch and oh the layers of varnish.
Heading back up the trail this Utah Juniper slows us down.
All along the hike back we have hoodoos and hoodoos in the making to our north and east.
Although it is the red rocks that catch our eye, we cannot overlook the ground and why it is ESSENTIAL to stay on established trails. As the Park Service tells us, the dirt is alive! It is a critical and fascinating desert feature. Yes, we are in the high desert on the Colorado Plateau.
We are beginning our decent into the trail’s canyons. Things always seem a bit different and new things catch your eye when walking in the opposite direction. Why it is good to slow down and look all around.
Notice the mountains in the background? They are the La Sal Mountains with peaks reaching 12,000 feet, the highest being Mount Peale at 12,721 feet. The La Sal Mountains are one of only three mountain ranges on the southern Colorado Plateau. The La Sal’s border Colorado, but the other two in this area, the Abajo (also called Blue) and Henry mountain ranges, are further south and west. Because they rise so far above the desert and canyon areas we are exploring, we can easily see them driving from spectacular place to place.
Keep on the trail to the right. That is one massive rock that fell along the trail up ahead!
We have not talked of fins, but here are great examples. Will they erode into hoodoos or become arches? Often it is the erosion of fins that form arches. You can see the beginning of an arch on that small fin center screen. At right is the trail into our hike’s last canyon area.
What a wonderful hike, but feeling a bit beat up by the 20-30mph winds, gusts to 40mph. Ready to jump into the SUV for some wind relief!
What a glorious afternoon! Watch for our next adventure in Arches National Park. Until next time . . .
