Journey to Utah in 2013, part 2: Valley of Fire State Park

This post is part of a series. To read the first post, click here. To see the gallery, click here.

WAKING UP IN FLAMES

Valley of Fire State Park was cold at night. The storm clouds had dispersed and exposed us to the stars and the chilly atmosphere. Our campsite, snug against a tall rock face, wasn't large enough to accommodate my tent along with the RV. I spent the night in the sleeping area above the front seats. Early the next morning I crawled out of my sleeping bag and peeked through the windshield at the sky: sapphire blue, above the walls of orange stone that surrounded us. The photography gods are smiling upon me today, I thought.

A full day's drive lay ahead of us on Interstate 15, through Arizona and into Utah, before we would reach Zion National Park. We had only a few hours to spend here. No time for a long hike, but at least I could take a flurry of pictures. My camera lay in readiness on the front seat, telephoto lens already attached, memory card nearly empty. I rushed to eat breakfast and gulp the essential coffee, then dashed out into the bright, crisp morning for a look at the rocks around Atlatl Campground.

Strong morning sun illuminated stone in a spectrum of flamelike colors. Some rocks were dark red, like dried blood. Others were orange, peach, pink, or brown. The shapes and textures of these formations were lovely, rounded in ways that vaguely reminded me of the rocks at Joshua Tree, though this red stuff seemed softer than the Joshua Tree monzogranite. Many rocks were sculpted into hourglasses, pyramids, and towers. Most had wavy lines carved into their surfaces, and were pockmarked by holes of varying sizes, some large enough to hold a person. At the base of these undulating walls, their colors continued in the form of sand.

Around the campground Bev and I wandered, breathing in the fresh post-rain morning air, our spirits high. We followed animal trails into narrow crevices, examined plants shooting out of the sand, and pried off thin slabs of stone from where they lay in stacks on the rock. The more I looked at these red rocks, the stranger they seemed. On the list of the most alien-looking vistas I'd seen in the desert, this one ranked near the top.

180 MILLION YEARS AGO: AZTEC SANDSTONE

At the edge of Atlatl Campground I could see red rocks popping out in front of gray mountains, a perplexing view. The unusual shapes and colors were only part of the strangeness; there was also the sudden appearance of red here in the middle of a mostly dull-colored terrain. How did this juxtaposition come to exist? We speculated aloud for a bit. The contrast of colors and shapes recorded some massive physiographical event, that much was obvious even to uneducated visitors like the two of us. But what kind of event, and how long ago?

As I unleashed my camera upon the landscape, I promised myself I'd learn the truth about Valley of Fire, and later, I did. I don't remember a lot of what I read, even though I read it many times over, but I did manage to grasp the fact that the red rocks here are part of the Aztec Sandstone. This formation came into existence around 180 million years ago, when this area of the continent was covered with a giant sand dune field, much like the Sahara Desert today.

I should pause here to clarify the term formation because it will come up again later. In geology, this word refers to a collection of distinct rock layers that are grouped together because they share physical characteristics and originate together in the same environment. A formation can have numerous members, and these might be linked together into groups. As with the Aztec Sandstone Formation, a formation tells the story of the time, place, and conditions of its origin.

Now back to the sand dunes of yesteryear. Subject to strong winds and occasional heavy rains, the ancient dune field saw huge quantities of sand blow hither, thither and yon for many years, creating fantastical shapes. Lines appeared in these shapes as one dune was leveled and another formed over it, over and over again, in a process called cross-bedding. The sandstone is covered with eolian marks, which are ripple marks that indicate the flow of wind (and water) on the surface of an object. You can see evidence of all of this in the photos above and below.

Sand dunes became sandstone through the action of lithification, in which the weight of the material above compacts the sand below and squeezes out water. This water will usually carry minerals with it, and these can act as cement in between the particles, helping turn soft sediment into stone. As these minerals dissolved, they also coated individual grains with iron oxides, staining them in shades of scarlet. That's how the Aztec Sandstone got its colors. The red motif was showing itself once more.

500-300 MILLION YEARS AGO: PALEOZOIC LIMESTONE

The gray rocks behind and above the Aztec Sandstone are another story entirely. They're limestone, and they're much older than the 180 million year old sandstone. They were formed during the Paleozoic Era, between 500 million and 300 million years ago, when this area was at the bottom of an ocean basin. Back then, the west coast was located in what's now western Utah. At the bottom of this section of ocean, marine animals left their shells and bones, which were compressed into limestone over inconceivably long ages. 

This limestone lurked at the bottom of the ocean for millions of years. But nothing stays the same forever. Around 225 million years ago, movements of the Earth's crust, more complicated than I'm currently able to articulate, caused the bottom of this ocean to rise. All the while, sand and other sediment was brought into the basin by rivers feeding the ocean; as the ocean became shallower and the land more arid, this watery landscape gave way to swamps and then deserts. Eventually, long after the birth of the limestone, the desert on top of it developed into the Aztec Sandstone.

The odd thing about Valley of Fire (and some other places too) is that you see evidence of the older limestone switching places with the younger sandstone. This evidence can be a little bit tricky to detect unless you're a geologist. It took me a while to understand that in the photo below, the red sandstone was once overlain by more of the gray limestone, which has since eroded away. In geology, it's a given that older rocks usually lie underneath younger ones. This is the Law of Superposition. Why is that law not obeyed here?

65 MILLION YEARS AGO: SQUEEZE AND UPHEAVAL

The answer is two words I find incredibly satisfying to say: thrust fault. A fault is a crack in the Earth's crust along which movement has occurred. A thrust fault is a special kind of fault situation that happens when compression of two tectonic plates causes rocks in a lower layer to be thrust up and over rocks in a higher layer. That's what happened here 65 million years ago, when the limestone layer was moved eastward and over the top of the sandstone layer by the force of compression. Eventually, erosion peeled back the limestone topping to reveal the sandstone forms underneath.

If this talk of a protective layer wearing off to reveal landforms sounds familiar, it might be because you read about it in one of my posts about Pinnacles National Park. A fault played a huge part in that scenario too, though it wasn't a thrust fault there, but a strike-slip fault. Both Pinnacles and Valley of Fire demonstrate the action of plate tectonics in a highly visible way. Pinnacles shows the workings of the San Andreas Fault, while Valley of Fire and other similar places nearby are evidence of a fault system called the Sevier Thrust Belt, which extends from about here to as far north as the border between British Columbia and Alberta. Once I understood the Sevier Thrust Belt and how Valley of Fire fit into it, I felt much more connected with my photos of the place. It's wonderful to know what I'm looking at when I see shots like the one above. 

1500 YEARS AGO: ATLATL STILL IN FASHION

Valley of Fire has seen more than just geological action. The park is rich with artwork left by humans who lived and visited here. Their canvas was the dark, shiny surface of the sandstone known as desert patina. Into this red-brown layer they scratched amazing quantities of drawings, all over Valley of Fire. Various native cultures left their mark here over the years, including the ancestral Pueblo people, sometimes known as the Anasazi people, who may have inhabited the area from about 1 to 1200 AD.

The rock art of these overlapping cultures demonstrates a common belief that this place was sacred, an appropriate location for rituals and vision quests. Maybe the red rocks had some spiritual connotation in their world; maybe they were all as impressed as I was by the scenery created by the thrust fault.

Atlatl Rock, site of many petroglyphs, can be seen in the photo above (the one with the stairs). The top right photo is a closer shot of the petroglyph surface of Atlatl Rock, and it includes possibly the most detailed rock rendering ever found of an atlatl, an ancient tool that was used for launching arrows and spears. You can't really see it in my photo because it's mostly obscured by a shadow, but a better picture would show you an atlatl with a spear ready to launch, and a bighorn sheep to serve as the target. This atlatl has helped experts guess at the age of the artwork here. Atlatls were mostly replaced by bows and arrows around 500 AD; rock art showing them may therefore be as much as 1500 years old. Of course, that's an infinitesimal sliver of time in comparison with the rest of the park's history, a thought that makes me stop and ponder human insignificance for several long, refreshing moments.

I would have loved to hike more at Valley of Fire, but our explorations were shortened by the pressure of our schedule. We stowed our loose objects and launched the RV onto Valley of Fire Road and out of the park. We were leaving the Aztec Sandstone behind. Glancing at the iron-rich rock disappearing in the rearview mirror, I thought back to the red curtain I'd seen flapping in an open window near Las Vegas.

To see lots more photos of Valley of Fire State Park, click here.

Comments

[joye]

Finally a moment to read and learn here. Atlatl! Who would have guessed that would be me my theme of the week. Now I know even more about it's origin. These last two blogs have been wonderful.
I love the textures and colors in these pictures and I am being hypnotized into learning about geography.