Halloween is today! Slip on your costume and hiking boots and let’s visit some geologically spooky locations. You’re in for a treat!
Sharon Lyon
Editor, GeoLifestyle
Hell, Grand Cayman
Hank Shiffman/ Shutterstock.com
I can safely say I’ve been to Hell and back again. I’ve even mailed a postcard from there.
The black, sculpted, jagged, pinnacle-like limestone spires of Hell, are found in West Bay, Grand Cayman.
The limestone, part of the Pleistocene Ironshore Formation, has a characteristic phytokarst surface, the result of bacteria, fungi, and cyanobacteria actively sculpting its unique topography. The microbes excrete acid as they bore into the rock.
Beneath Hell’s black, craggy surface, the limestone is gray.
The Pleistocene limestones were deposited on top of a gradually subsiding core of Oligocene and Miocene limestones.
One fun thing: This site is the only place (that I know of) where you’re greeted with “How the Hell are you?” when you enter the post office.
Devil’s Bridge, Sedona, Arizona
The Schnebly Hill Formation underlies Devil’s Bridge, Arizona. Photo courtesy of Marie Thomas.
There are so many geologic features named for the devil; it’s downright scary! Devil’s Tower National Monument and Devil’s Postpile National Monument come immediately to mind, but there’s also Devil’s Backbone, Devil’s Windpipe, Devil’s Playground, and Devil’s Garden. An extensive list with descriptions can be found here.
My daughter, Marie Thomas, recently visited Devil’s Bridge, a narrow, wind-eroded arch and popular hiking destination located north of Sedona, Arizona. Here’s a little about its geology:
In the Permian, along the shoreline of the Supercontinent of Pangea, the region was covered with layers of muds and sands from slow-moving rivers across vast floodplains. The sediments would later become the Hermit Formation, Sedona’s brick-red bedrock.
The area continued to experience deposition, adding more than 200 meters of colorful sandstone interspersed with thin white layers of limestone conglomerate. Evidence of tidal currents can be found in the appearance of ripple marks and parallel banding as sediments were washed along coastal tidal flats. This formation, known as the Schnebly Hill, comprises the bulk of the “Red Rocks” of Sedona and forms Devil’s Bridge.
Erosion has carved these red rocks, leaving behind spectacular canyons, spires, and buttes.
The Schnebly Hill Formation is capped by the white, cliff-forming, petrified dunes of the Coconino Sandstone.
What they’re saying: “It was an incredible hike to get up there. I experienced an adrenaline rush while standing on the narrow ledge of the bridge, looking out into the abyss. It was terrifying and beautiful at the same time,” Thomas says.
Go deeper: Read more about the geology of Devil’s Bridge and Sedonahere.
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Hall of Horrors and Skull Rock, Joshua Tree National Park, California
Clockwise from upper left, Skull Rock, "alien" plant, weathered granitic boulders, Hall of Horrors sign, Joshua Tree National Park. Photos courtesy of Laurie Stenberg and Asim Ali.
Joshua Tree National Park is situated within the eastern part of California’s Transverse Ranges at the transition between the Mojave and Sonoran deserts.
About the park:
The Joshua tree, a unique desert plant with beautiful white spring blossoms, is endemic to the higher, moister, and cooler Mojave Desert.
The crystalline basement in the park consists of Proterozoic plutonic and metamorphic rocks. These were intruded by a composite Mesozoic batholith of Triassic-Late Cretaceous plutons.
The basement was exhumed during the Cenozoic and underwent differential weathering. The deepest weathering profiles formed on the quartz-rich, biotite-bearing granitoid rocks, creating the odd-shaped boulders you see today.
At Skull Rock, raindrops accumulated in tiny depressions and began to erode the granite. As more rock eroded, more water accumulated until, as time passed, two hollowed-out eye sockets formed and the rock began to resemble a skull.
Geologist Laurie Stenberg (AECOM) and her husband Asim Ali visited Joshua Tree a few years ago. Stenberg says, “I love all the rocks at Joshua Tree, from the spooky, the amusing (thumb rock), to the sublime. And the plant life can look pretty weird too. The plant in the photo—I have no idea what it is—looks like a weird scrawny alien with its arms up. Ali adds “we were there in late August and the high temperature hit somewhere between 113–117 degrees.”
The bottom line:Hall of Horrors and Skull Rock are favorite stops for Joshua Tree National Park visitors. Both are easy trails that meander around boulders and desert washes and climb over boulder slabs. Hall of Horrors contains two short slot canyons—one only 6 inches wide. That would be a horror for me!
Plot: Dr. Simon Nealy, hoping to solve the mystery of his long-missing sister, takes a curator’s job at the museum where she disappeared. But things are not what they seem at The Hawthorne. Noises disturb the evening hours and ghostly apparitions haunt the galleries. An elderly patron speaks with the souls. Old museum records give hints to a past-curator’s madness. Will Simon discover the truth about his sister before he loses himself to a prehistoric killer? Or is it all in his mind?
I hope you enjoyed this week’s Spooky Geologic Sites. The next time you pick up a rock, you can ask yourself, ‘is the ground telling its own ghost story?’
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