Exploring the Earth and Sky of the West

Posts tagged “sandstone

The Heart of Utah: Capitol Reef National Park

Hickman Bridge, Capitol Reef National Park, Utah

Hickman Natural Bridge, Capitol Reef National Park, Utah

The least visited and most isolated of Utah’s five national parks, Capitol Reef hosts what is perhaps the quintessential Utah landscape. It is as if someone took small portions of the other four parks and mashed them into one; here you can find a plethora of arches and natural bridges, deep snake-like canyons, soaring Navajo and Wingate Sandstone cliffs, and even a few hoodoos thrown in for good measure.

Looking east across the Waterpocket Fold toward the Henry Mountains

Looking east across the Waterpocket Fold toward the Henry Mountains, the last mountain range in the lower 48 to be mapped and named, and their high point: 11,522′ Mt. Ellen.

The skinny sixty mile long park was originally established as a national monument in 1937, but became a national park in 1971. The odd shape stems from the inherent nature of the feature it protects: the Waterpocket Fold, a 100+ mile-long kink in the Earth’s crust known as a monocline. Creeks and rivers have dissected the fold over millions of years to reveal what is quite possibly the most colorful and diverse array of rock layers in Utah.

Capitol Reef is far from just about everywhere (which made the flat tire we experienced on the way that much more annoying). To the east and south lie the last major mountain range and river, respectively, to be mapped and added to the map of the lower 48 states. Not until the 1960s did a paved highway cross the Waterpocket Fold through Capitol Reef. In the northern part of the park, the Fremont River slices a narrow canyon through the Waterpocket Fold, its water creating one of the few habitable areas in the entire region. Petrogylphs attest to the importance of this year-round water source to ancient inhabitants. In 1880, Mormon settlers established the settlement of Fruita along the banks of the Fremont. The remains of this historic farming community and the abundant, lush green orchards and fields seem out of place in the otherwise stark central Utah canyonlands but add to the allure of the park.

Early morning in the Fruita orchards and pastures

Early morning in the Fruita orchards and pastures

Bighorn sheep petrogylphs along the Fremont River, Capitol Reef National Park, Utah

Bighorn sheep petrogylphs along the Fremont River, Capitol Reef National Park, Utah

Here are some of the sights from our quick trip to Capitol Reef this past weekend:

Patterns in colorful sandstone, Capitol Reef National Park, Utah

On a hike through Capitol Gorge, we encountered a bed within the Navajo Sandstone with some unbelievably complex and colorful patterns:

For the most part, the landscape at Capitol Reef is quite open, allowing vast views and superb light at sunset:

Chimney rock at sunset, Capitol Reef National Park, Utah

Chimney Rock, a tower of soft Moenkopi Formation mudstone capped by harder sandstone belonging to the Shinarump Member of the Chinle Formation

Sunlight on cliffs, Capitol Reef National Park, Utah

Late afternoon scene along the Chimney Rock Trail, Capitol Reef National Park, Utah

Sunlit cliffs at Capitol Reef National Park, Utah

More sunset scenes

Crumbling cliffs of Wingate Sandstone, Capitol Reef National Park, Utah

Hiking among crumbling cliffs of Wingate Sandstone, Capitol Reef National Park, Utah

Moon rising above cliffs, Capitol Reef National Park, Utah

A nearly full moon made it hard to do much stargazing at Capitol Reef, which is world-renowned for dark night skies.

Not far from the park campground and visitor center are the remnants of an old trail leading up a sandy wash, then up a short but steep talus slope before arriving at a hidden basin containing hoodoos and other strange rock formations. Unfortunately it was just about noon and the light was about as direct and harsh as possible, but it was cool to explore an area off-the-beaten path yet still in sight of the tour buses below:

Climbing up a talus slope, Capitol Reef National Park, Utah

Ascending the talus…

Balanced rock hoodoo, Capitol Reef National Park

Gravity-defying hoodoos were the reward!

Hoodoos at Capitol Reef National Park, Utah

Hoodoos in the Chinle Formation at Capitol Reef National Park, Utah


Coyote Gulch in Pictures

ALcove and Jacob Hamblin Arch, Coyote Gulch, Utah

Jacob Hamblin Arch and a series of deep alcoves cut into the Navajo Sandstone are the highlights of a trip through Coyote Gulch.

This past weekend we made our first foray into the interior of the Colorado Plateau since moving to Utah. Our destination was Coyote Gulch, a well-known tributary of the Escalante River that straddles the boundary of Grand Staircase-Escalante National Monument and Glen Canyon National Recereation Area. Below are some photos from the trip:

Trail through Hurricane Wash, Utah

The hike begins with a nearly six mile slog through the desert along, and often in, Hurricane Wash. Toward the end it gets interesting, but mostly it looks like this. Nice, but nothing to write home about.

Sign along Hurricane Wash, Utah

After about three miles of walking along Hurricane Wash, the trail leaves Grand Staircase-Escalante National Monument and enters Glen Canyon National Recreation Area. It is here that things start to get more interesting.

Cliffs in Hurricane Wash, Utah

Soon, cliffs of Navajo Sandstone begin to rise up along the wash and become progressively higher as you head downstream. Eventually a small stream appears in the canyon bottom, after passing through several short sections of dry narrows like this one.

Alcove along Coyote Gulch, Utah

Eventually, Hurricane Wash meets Coyote Gulch, which is perhaps best known for a series of enormous undercuts carved into the smooth and sheer walls of pink Navajo Sandstone.

Alcove along Coyote Gulch, Utah

This was the largest alcove we encountered and we were fortunate enough to be able to camp in its shadow. For most of the trip, the air was incredibly calm and still and standing inside these alcoves felt like being inside a great rotunda or cathedral.

Large alcove with hiker for scale, Coyote Gulch, Utah

The scale of the alcoves is truly incredible and difficult to grasp without being there. Note Michelle for scale in the lower left.

Star Trails as seen from an Alcove along Coyote Gulch, Utah

A group camped directly beneath the alcove on our first night spent several hours messing around with some extremely bright flashlights and spotlights. It was rather annoying when we were trying to fall asleep, but it actually made the star-trail sequence I was shooting come out rather nice.

Jacob Hamblin Arch in Coyote Gulch, Utah

Just a few hundred yards downstream from the large alcove where we camped was Jacob Hamblin Arch (also see photo at top of page). The creek makes a tight meander around the fin of rock containing the arch, allowing it to be seen from both sides.

Coyote Natural Bridge, Coyote Gulch, Utah

On day two, we day-hiked from our campsite near Jacob Hamblin Arch down to the confluence of Coyote Gulch and the Escalante River, a distance of about 13 miles round trip. One of the many attractions en route was Coyote Natural Bridge.

Green grass and trees in spring, Coyote Gulch, Utah

It was mid-April and the canyon was incredibly lush and green. Many of the stream terraces alongside the creek were resplendent with green grasses and wildflowers.

Spring and rock formations, Coyote Gulch, Utah

Numerous springs emerge from the canyon walls along Coyote Gulch. Do you see the “T-Rex” in the upper left?

Lower Coyote Gulch, Utah

Moving downstream, Coyote Gulch leaves the Navajo Sandstone behind and carves into deeper and older layers of rock. Near the confluence with the Escalante River, the canyon walls are in the bright orange Wingate Sandstone.

Confluence of Escalante River with Coyote Gulch, Utah

Looking downstream along the Escalante River at its confluence with Coyote Gulch.

Stevens Arch, Escalante River Canyon, Utah

A ford of the waist-deep Escalante and a short walk upstream from the confluence reveals the impressive Stevens Arch high on the canyon wall.

Stevens Arch

Another view of Stevens Arch.

The surface elevation of Lake Powell when full is about 3,700 feet, almost exactly the elevation at the confluence of Coyote Gulch and the Escalante River, as shown by this Bureau of Reclamation benchmark.

At various times in Lake Powell’s history, most recently in the 1980s, the lake surface rose just high enough to flood the lowest reaches of Coyote Gulch and inundate the confluence under shallow water. The remnant water level lines are still faintly visible in lower Coyote Gulch.

Rocks, trees, and desert varnish, Coyote Gulch, Utah

The hike to the Escalante and back was a long one, but views like this around pretty much every bend made it seem shorter!

As a final note, Coyote Gulch has, for good reason, become an extremely popular destination over the years. We actually had some second thoughts about going after reading guidebooks that implored us not to visit on a holiday weekend in the spring (it was Easter) and after the BLM employee who issued our permit told us we would be “joining a party.” In the end, we found the over-crowding hype to be somewhat overblown. While there were more folks down there than you might expect to find in such a remote location, it could hardly be called a party. We camped in the most popular half-mile section of the gulch and couldn’t see anyone else from our site along the banks of the creek. We met just a handful of other groups on our hikes in and out of the gulch, and only occasionally encountered other people on our all-day hike down to the Escalante River and back. If you are seeking complete and total solitude or isolation, this is probably not the place for you. But we didn’t feel like the crowds detracted from the experience much if at all.

The increase in visitation to Coyote Gulch certainly creates challenges for the future. Hikers are now required to carry out all human waste, which seems to be a step in the right direction. However challenging keeping the gulch in pristine condition might be, I tend to believe that this situation is better, in the long-term at least, than the alternative. Coyote Gulch has been described as one of the last remaining echos of Glen Canyon, a small remnant of the scenic wonders that were submerged after the construction of Glen Canyon Dam and the filling of Lake Powell in the 1960s. Glen Canyon was lost ultimately because it was “the place no one knew.” The same cannot be said of Coyote Gulch. It is one of those places where the term “loved to death” gets thrown around, but ultimately we only fight to protect places that we love and value and it is hard to truly appreciate a place like Coyote Gulch solely through pictures. Hopefully the more people that go to Coyote Gulch and experience its majesty first-hand, the more people there will be to stand-up for it against future threats that are assuredly to come.


Colorful Geology at Valley of Fire State Park

Compaction bands and sandstone, Valley of Fire, Nevada

Compaction bands in multi-colored Aztec Sandstone, just one of many geologic wonders in Valley of Fire State Park, Nevada

One of the great things about living in Southern Utah is the abundance of different climates within a small geographic area. When temperatures rise into the 90s and 100s in the low-elevation valleys, we can be in cool alpine meadows at 10,500′ in less than an hour. When snow, slush, and mud cover the trails in winter, vast portions of the Mojave and Great Basin Deserts are within a day’s drive. One of these desert areas is Valley of Fire State Park in southern Nevada, not far from I-15 between St. George and Las Vegas.

Perhaps not surprisingly, upon arrival at Valley of Fire one is greeted with an array of whimsically sculpted red rock formations. Now red rocks are hardly unique in this part of the country, and the crimson cliffs here are no more notable than those found anywhere else in Utah or Arizona. But head into the interior of the park and you soon realize the allure of the Valley of Fire. After cresting the red cliffs, the hues begin to multiply exponentially and before long you are surrounded by just about every color of sandstone imaginable.

Colorful rocks at Valley of Fire State Park, Nevasa

A layer-cake of spectacular colors in Valley of Fire State Park, Nevada

To put it bluntly, the colors at Valley of Fire are simply ridiculous…and attributable to its unique geologic location. The rocks here are mostly equivalent to those found throughout southwestern Utah and the Colorado Plateau. The Aztec Sandstone, the dominant rock unit exposed in the park, is the equivalent of the Navajo Sandstone that makes up the cliffs of Zion National Park. Geologists just assign it a different name when it appears in Nevada and the Great Basin. Perhaps the distinct name is appropriate though, given that the sandstone seems to take on a life of its own here.

Valley of Fire State Park lies within the Basin and Range province, a vast region covering Nevada and portions of half a dozen other western states where the Earth’s crust is being slowly but violently stretched apart. As the writer John McPhee once noted, so much stretching has occurred here that 20 million years ago, Salt Lake City and Reno would have been more than 60 miles closer together. Faults are abundant in this land, and fluids associated with some of these faults have at various times leached iron compounds from the originally all-red sandstone, causing some layers to become bright white, and re-deposited them in other layers, leading to the wide variety of colors.

Some of the most impressive colors are found just to the west of the “Fire Wave” feature near the northern terminus of the park’s scenic drive:

Vibrant colors in the Aztec Sandstone in Valley of Fire State Park, Nevada

Vibrant colors in the Aztec Sandstone in Valley of Fire State Park, Nevada

Fire Wave in Valley of Fire State Park, Nevada

A feature known as the “Fire Wave,” Valley of Fire State Park, Nevada

While there are numerous hiking trails, there is also lots of off-trail terrain to explore. Some of the most spectacular scenery can be found by parking at one of the numerous pull offs and just wandering out into the rock wonderland. One particular geologic feature of note is what are known as “shear-enhanced compaction bands,” thin brittle fins of rock that rise almost vertically out of the ground and often run continuously for dozens to hundreds of yards. At first glance, these features look like mineral veins, but upon closer examination they are composed of the same material as the surrounding sandstone, but are obviously slightly harder than the host rock. In many places there are two perpendicular sets of the bands, forming a checkerboard like pattern superimposed on the sandstone.

Compaction bands in the Aztec Sandstone, Valley of Fire State Park, Nevada

Compaction bands in the Aztec Sandstone, Valley of Fire State Park, Nevada

The bands are the result not of stretching, but of compressional forces that predate the formation of the Basin and Range. Stresses associated with an earlier mountain building episode (known as the Sevier orogeny) created these funky bands by essentially “squeezing” together (and even breaking) the sand grains that make up the rock, eliminating much of the empty space between the grains and forming a miniature layer of tougher, harder, and more compact sandstone that is slightly more resistant to weathering and erosion. As a result, the bands tend to just out from the surrounding slickrock by several inches, and even several feet in some locations. For such a seemingly obscure feature, many papers have been written about these compaction bands (and similar ones in a few other locations in the region). However my understanding of the structural processes behind their formation is limited and the most recent articles about them appear to be behind a paywall. If anyone reading this has more insight into these things, I would love to hear from you.

As mentioned before, these bands are quite thin, in most less than a centimeter thick and thus, sadly, quite brittle. They are easily broken by an errant boot step so if you find yourself among them, tread carefully so that future visitors will be able to experience this unique and colorful landscape.

Colorful sunset on red rocks, Valley of Fire State Park, Nevada

Sunset from the Old Arrowhead Road in Valley of Fire State Park, Nevada

 

 


A Sandstone Wonderland: Snow Canyon State Park

moqui marbles in snow canyon state park, Utah
moqui marbles in snow canyon state park, Utah

Thousands of moqui marbles, concretions of iron oxide minerals, accumulate in small troughs eroded into the Navajo Sandstone, Snow Canyon State Park, Utah

Southern Utah is a mecca for tourists from around the world, and most of that blame can be placed on the shoulders of a single layer of rock: the Navajo Sandstone. Quite possibly one of the most famous geological formations in the world, the Navajo Sandstone is responsible for the soaring cliffs of Zion National Park, the monoclines of Capital Reef, and the undulating, swirling, entrancing patterns of the The Wave in Arizona and Grand-Staircase Escalante National Monument in Utah. The Navajo Sandstone also rears its beautiful head in lesser known gems, such as Snow Canyon State Park just a few minutes northwest of St. George, Utah.

Snow Canyon is actually several canyons in one, all cut into the Navajo Sandstone. The original Snow Canyon existed up until about one million years ago, when it was rudely filled in by a series of basaltic lava flows originating from the northeast. Water, being the couch potato that it is, doesn’t like to carve through hard volcanic rock, so the stream that had excavated Snow Canyon promptly jumped ship to find some more Navajo Sandstone, and thus began establishing a new canyon slightly to the west. The stream went about its business carving Snow Canyon #2 until about 10,000-20,000 years ago, when it was thwarted by yet another lava flow. True to history, the stream changed course a second time, and is now busily carving Snow Canyon #3 even further to the west. The result is a multi-tiered canyon, with the remnants of the canyon-filling lava flows forming the tread of each step.

panorama of snow canyon state park, utah

360 degree panorama of Snow Canyon State Park from the top of a “turtleback” of Navajo Sandstone, a small knob of rock that was surrounded by basaltic lava flows that diverged around it during eruptions 10,000-20,000 years ago. The small dark black patch just to the left of center is the entrance to a lava tube. The current iteration of Snow Canyon is seen at left. 

The Navajo Sandstone itself is a colossal formation, several thousand feet thick in places, representing the lithified remains of a large Jurassic sand dune sea (known as an erg), likely analogous to the modern day Sahara desert. If you think Southern Utah is hot and dry today, imagine being there 180 million years ago when the climate was hot and hyper-arid. Add some dinosaurs and you’ve got yourself a fun day in the Jurassic desert. Over time, mineral-rich fluids percolated through the sand, depositing mineral cement in between the sand grains, binding them together into stone. The Navajo Sandstone is known for its spectacular aeolian (fancy geology-speak for “wind-blown”) cross-bedding, inclined layers that form when winds blow sand up the shallow face of a dune, only to have it tumble down the steep slip face on the other side.

cross beds in navajo sanstone, snow canyon state park, utah

Cross bedding in the Navajo Sandstone becomes even more pronounced as sunset nears and shadows lengthen

view of navajo sandstone ridges cliffs in snow canyon state park, utah

Looking south across swales and ridges of Navajo Sandstone from the Petrified Dunes trail in Snow Canyon State Park, Utah

A especially peculiar property of the Navajo Sandstone is the presence of occasional beds containing abundant spherical concretions of sand held together by the iron oxide minerals goethite and hematite (see photo at top of page). Commonly known as “moqui marbles,” these small spherules are slightly harder than the rest of the sandstone, so as the rock weathers away, the concretions are left behind to accumulate in large quantities on the surface of the rock. Moqui marbles can be found in many locations throughout Utah. And on Mars. The discovery of nearly identical hematite concretions by the Opportunity rover was some of the first definitive evidence that liquid water once flowed on the red planet, since the formation of the marbles requires groundwater to dissolve, and then re-precipitate iron minerals in the subsurface. If you are intrigued by my incredibly vague and simplistic description, you can find much, much more on the moqui marbles and their mode of formation here. If not, you are hereby forgiven and are welcome to enjoy the final photo without guilt:

black boulders of hematite rich beds in the navajo sandstone, snow canyon state park, utah

Hematite rich beds in the Navajo Sandstone are more resistant to weathering & erosion, forming large brown, black, and red boulders that are scattered across the landscape


Honeycomb Weathering from the Desert to the Sea

Continuing on with our recent geological theme here at Pyroclastic Pixels (you’d almost think I was a geology grad student or something…), today we are going to take a look at one of the most picturesque geological curiosities you’ll ever find: honeycomb weathering, also frequently referred to as “tafoni”.  Those two terms aren’t really exactly quite completely equivalent but we’re not going to journey down the nit-picky fork in the road today.  Honeycomb weathering is pretty cool. About the only thing that would make it better is if the holes were actually filled with honey. That joke sounded way better in my head than it looks on the screen.

Honeycomb1

Honeycomb weathering in sandstone at Teddy Bear Cove, Chuckanut Bay, WA (all pictures are from this locality unless otherwise noted)

Specific geographic and geologic conditions are needed for honeycomb weathering to develop, yet these conditions can be satisfied in a variety of places, from the arid deserts of the American Southwest, to the storm-battered shores of the Pacific Ocean. Here in northwestern Washington State, honeycomb weathering occurs along the coast, along and just above the high tide mark, in areas where a rock unit known as the Chuckanut Formation is present.  The pictures on this page were taken at Teddy Bear Cove, just south of Bellingham, WA, which has some of the most spectacular examples I’ve ever seen. The Chuckanut Formation, or “the Nut” as I like to call it when I’m feeling lazy, is a thick series of sandstones, conglomerates, and occasional coal seams that were deposited about 60 million years ago when NW Washington occupied a large basin at the foot of an ancient mountain range that occupied more or less the same space that the Modern Cascades now occupy.

There is a good reason that sandstone is one of the rock types most susceptible to this type of weathering. Sandstone is essentially composed of countless tiny, sand-sized particles of various minerals (mostly quartz and feldspar in the case of “the Nut”) which are held together by some sort of substance, known as cement, that “glues” them all together into a solid mass. In most sandstones, this substance is either calcium carbonate (CaCO3) or silica dioxide (SiO2), also known as quartz. Honeycomb weathering forms when salt-laden sea spray lands on the sandstone. As the salty sea water evaporates, tiny salt crystals form on the surface of the rock. The growth of these salt crystals on the surface of the rock physically separates the sand particles from the cement. Over time (a long time…), this creates a small depression in the rock. Once a small indentation forms, a positive feedback effect is created; the hole has a greater surface area than a flat surface and thus more rock is exposed to incoming sea spray. Sand grains are thus separated from the cement at a faster rate, thereby enlarging the hole. In some locations, you can actually see little piles of sand grains in the cavities, grains that were once part of the rock but have now been forcibly removed by the salt. I’ve found that this is most prevalent in areas just above the high tide line where wave action can’t wash the sand grains back out to sea.

Honeycomb2

But Zach, you say…how then does honeycomb weathering form in places like the desert Southwest where the closest thing to sea spray you’re going to find is mule deer pee?  Ah…well I’m glad you asked. We often observe honeycomb weathering in sandstone in places such as Southern Utah that are far away from the sea. I had some difficulty finding a halfway decent picture of desert honeycomb weathering from my archives, but I was able to find one that I took in 2008 in Capitol Reef National Park (see below). If you want to see a lot better examples, just do a Google image search for “Utah tafoni”. While the exact cause may vary, and the individual pits tend to be larger, the process involved is essentially the same. We still need to find some way to separate our sand grains from the cement. Many washes in the southwest are dry for most of the year but are very rich in dissolved salts when they do flood. In desert environments, it’s no surprise then that we tend to find honeycomb weathering predominantly along dry stream beds and canyons. When a flood comes through, even though the water may not be as saline as the ocean, it is still salty enough to form small salt crystals when it evaporates, which it invariably does. In other locations, slightly acidic groundwater percolating through rocks can actually chemically dissolve calcium carbonate cement, leaving the sand grains with nothing to cling to.

Larger scale cavernous weathering features in Capitol Reef National Park, Utah

Larger scale cavernous weathering features in Capitol Reef National Park, Utah

Honeycomb3

Hard as it might be for you to believe, this has been only a cursory explanation of the honeycomb weathering formation process. If your brain hasn’t begun to resemble honeycomb weathering by now and you are interested in the gritty details (perhaps you arrived here in the process of researching a paper or maybe you’re a geology nerd like me and just like knowing about such things), an excellent academic paper on the formation of honeycomb weathering can be found here.  Regardless, your next step should be to pull out a geologic map, find the closest beach with some sandstone, pull your boots on and go find yourself some honeycomb weathering! Or you could always just look at the rest of these pictures I suppose…

Honeycomb4Honeycomb6Honeycomb5