Rocks and (Musk)Rats of the Rockies
Textbook stream meanders along the Fall River, Rocky Mountain National Park, Colorado
A few weekends back I led my semester-ly geology field trip to Rocky Mountain National Park. Each time I end up finding new gems that I had previously overlooked, such as the spectacular stream meanders along the Fall River pictured above. One good flood and the stream will erode through the narrow strip of land separating the two meanders, leaving the bend in the middle of the photo high and dry. Places like this are a great opportunity for students to see in action a geologic process that every introductory geology instructor teaches in the classroom.
Despite many areas of the park still being covered in umpteen feet of snow, wildflowers are beginning to appear in the lower elevations around Estes Park:
Early blooming pasqueflower in Moraine Park, Rocky Mountain National Park, Colorado
Longs Peak shrouded in a late-season storm, Rocky Mountain National Park, Colorado
The biggest cause for excitement actually occurred after the field trip was over. I had intended to stick around in the park for a longer hike after setting the students free, but I quickly realized I had left my filled camelback on the kitchen counter. Lacking any sort of water carrying device, not wanting to shell out the cash to buy one, nor desiring to try to fashion one out of ungulate intestines, that plan was foiled. In lieu of a hike I headed for a short stroll around Lily Lake to try to get some pictures of the incoming storm enveloping Longs Peak.
While snapping the above photo, I was startled by what sounded like a cannonball being dropped into the lake behind behind me. My initial suspicion of hooligans launching boulders into the lake was discredited when I turned around and saw no one within half a mile. I made my way to the edge of the lake and remained motionless; after a few moments, this little guy appeared:
Beaver? Otter? Furry fish?
Lily Lake, Rocky Mountain National Park, Colorado
Noticing the presence of a nearby mass of chewed up sticks (above), I hastily assumed I was in the presence of a beaver. In short time, a second critter appeared and the pair began to tussle, albeit sadly behind a willow bush from my point of view. It soon became clear that these animals were more agile and less chunky and rotund than your typical beaver. Not being able to see them clearly with the naked eye, my next guess was river otter, which persisted until I got home and took a closer look at the pictures below. Otters would have a tough time leading their carnivorous lifestyles with only those gigantic incisors to work with. I was out of ideas (this is why I lead geology field trips, not wildlife watching trips…) , so I was forced to the internet where I learned that I had just seen my first muskrat.
Two combative muskrats in Lily Lake, Rocky Mountain National Park
Nice teeth!
Finally, on the way home, I made a quick stop at a rock shop in Estes Park that I’ve driven past dozens of times. I quickly discovered that knowledge of basic geological principles is not a prerequisite for owning a rock shop when I found a large bin of black limestone labeled:
{facepalm}
A Sandstone Wonderland: Snow Canyon State Park
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.
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 bedding in the Navajo Sandstone becomes even more pronounced as sunset nears and shadows lengthen
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:
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
Giants of the Desert(s)
Star trails and high clouds from Jumbo Rocks Campground, Joshua Tree National Park
Driving across the southwestern United States, one could be forgiven for thinking that all deserts are the same. However, differences in elevation, temperature, topography, and precipitation make them distinct in ways that are often hard to comprehend from a fast-moving car.
For all their differences though, both the subtle and the striking, the Mojave and Sonoran Deserts share one thing in common; the most visible symbol of each is a large, majestic, and photogenic plant perfectly suited for the harsh conditions in which it evolved to inhabit.
A spectacular winter sunset at Joshua Tree National Park
For the Mojave Desert, that plant is the Joshua tree (Yucca brevifolia). Not actually a tree but rather, as the scientific name betrays, a species of Yucca, early settlers bestowed the befuddling name upon this plant after noticing that the contorted arms resembled the prophet Joshua raising his arms to the sky in prayer.
Today, the Joshua tree is considered an indicator species for the Mojave Desert, as many other inhabitants of the Mojave (two-legged, four-legged, and winged alike) depend on it for survival. The Joshua tree grows through portions of western Arizona, southeastern California, and southern Nevada, but some of the largest and healthiest stands are protected within the boundaries of Joshua Tree National Park and Mojave National Preserve.
Sunset colors illuminate the landscape at Joshua Tree National Park
A nearly full moon hovers over a Joshua tree at sunset
For the Sonoran Desert, the symbolic plant is the saguaro cactus (Carnegiea gigantea). Despite the nearly ubiquitous use of the saguaro as a symbol of the American Southwest, this excruciatingly slow growing cactus actually only grows in a small portion of the Sonoran Desert extending from extreme northwestern Mexico into south-central Arizona.
Sunset from the Gould Mine Trail in Saguaro National Park. On the horizon is Kitt Peak, home to one of the largest astronomical observatories in the United States
Like the Joshua tree in the Mojave, the saguaro is an integral part of the Sonoran Desert ecosystem. Birds such as the Gila woodpecker nest within the flesh of the cactus while the fruits and flowers provide a source of food for many other species, including humans. When the end finally comes for a saguaro (which can take well over 100 years), the flesh rots away to reveal an internal structure consisting of a series of wooden ribs, which often remain standing long after the saguaro dies:
A young saguaro mimics a neighbor who has seen better days
Both the saguaro and Joshua tree face serious threats; in the long term from a climate that may change faster than they are able to migrate, and in the short term from a loss of habitat due to rapidly ballooning human populations in the desert regions that these giants inhabit.
Zach Schierl Photography 