Autumn is my favorite time of year. From my childhood in western New York, it means apples and cider, sweaters and school days, sunny skies and crisp air. Most of all autumn means color. The world suddenly becomes more vibrant. The sky seems to turn a deeper, darker shade of blue, and green leaves slowly turn to bold new colors: crimson, burnt orange, and gold. Now, as a ranger working in Zion National Park, I find autumn is no different. The temperatures cool, the days grow shorter, and the colors change. And while the desert is not a place many associate with autumn colors, I believe it rivals New England any day. Against the blue skies and red rocks of Zion Canyon, the changing leaves are bursting fireworks of yellow, orange, and red. But why all these magnificent colors? And why now?
As I lazily lounge beneath the shade of a cottonwood tree near the Zion Lodge, I gaze at those shiny green leaves rustling above my head. They are absorbing almost all of what we call visible light, which includes every color of the rainbow. We see color because all objects in the world absorb and reflect different sections of the rainbow, and our eyes see what is reflected. The chlorophyll pigment in leaves absorbs all colors except green, so green is what we see. During spring and summer the cottonwood leaves are producing chlorophyll. But as the summer draws to a close, the shorter days and longer nights signal the plant to slowly stop producing that pigment. Luckily for us, that’s when the other pigments in the leaves become unmasked. Each green leaf will develop splashes of yellow and brown, a result of carotenoid pigments, present in the leaf all year but seen only in the fall after the chlorophyll disappears. Carotenoids give vegetables like carrots and corn their color and gradually turn all the cottonwood trees and box elders along the banks of the Virgin River into a vibrant gold. Because of another pigment called anthocyanin, produced only in the fall, the shiny green bigtooth maples along the Emerald Pools Trail will leisurely morph into crimson. Anthocyanins color fruits like apples and cherries. These are the pigments that paint the autumn landscape. Depending on the rainfall and the temperatures, Zion Canyon’s fall colors usually peak around mid-November.
Sitting under a cottonwood tree on a blistering 100 degree day, I find it hard to imagine it will ever be fall. Inevitably, though, the sun will rise a little later and set a little earlier. I will stop feeling as though I might melt when I walk out the door. And those shiny green leaves keeping me cool will slowly turn gold. Right now, though, as I lie beneath the fluttering leaves, I will keep dreaming about autumn, its cool temperatures, and its palette of colors.
Zion's Misunderstood Rodents
Learn about the misunderstood rock squirrel with Park Ranger Robin Hampton in her reading of an article written for the park's Nature Notes by Park Ranger Amy Gaiennie.
The visitor pointed to my photograph of the hand with the nasty bite and stitches. “What did that?” he asked. “A rock squirrel,” I replied, pointing to a photograph of a chubby-looking rodent with bright brown eyes. “I’ve seen a lot of them on this trail,” the visitor continued. “That’s why we show these photos as part of the River Rendezvous program,” I explained. “Some people feed and even try to pet the rock squirrels here, and we want them to know that’s dangerous. It’s not good for the rock squirrels, either.”
I had set up my photographs on a bench about three-quarters of the way up the one- mile Riverside Walk. It faced a sandy alcove tucked back against towering cliffs of Navajo Sandstone. Behind the bench, the Virgin River tumbled, sounding unusually loud as it echoed between narrowing canyon walls. For the next hour and a half, I would be answering visitor questions and talking about the plants and wildlife they might encounter. One of the most commonly observed animals along the trail is the rock squirrel (Spermophilus variegatus).
The Riverside Walk offers ideal rock squirrel habitat. They prefer rocky locations including cliffs, canyon walls, and boulder piles. They dig burrows and raise their babies under large rocks, and they use rocks as lookout points. Classified as ground squirrels, they can climb trees almost as well as tree squirrels, and will forage and seek shelter high on limbs and branches as well as on the ground.
Less than fifteen minutes into my program, I noticed a rock squirrel digging in the sand next to my bench. With its sharp front claws it unearthed a round, dark object, then suddenly leaped to one edge of the bench. There it sat, rapidly twirling the object in its paws while gnawing.
Visitors were now gathering to watch and photograph the squirrel. Apparently quite unalarmed by the attention it was getting as it ate, it seemed to exemplify the words visitors frequently use to describe it: “Cute. Tame. Friendly.”
Although rock squirrels may be cute, they are anything but tame and friendly. Their apparent friendliness is actually a lack of fear of humans and a desire to secure food. Their sharp, chisel-like incisors are capable of slicing through barriers—including human skin—in a matter of seconds and are well-adapted for their incredibly varied natural diet: vegetation, flowers, acorns, pinyon pine nuts, cactus and cactus fruit, berries, and roots and tubers. They also eat invertebrates, such as beetles and grasshoppers. They will hunt and kill small rodents and birds, even young wild turkeys, and eat carrion.
Against one predator, the western diamondback rattlesnake, rock squirrels have developed a formidable defense. In a behavior that is called “mobbing,” the squirrel will lunge forward repeatedly and wave its tail from side to side, kicking sand and rocks at the snake’s head. It will even bite the snake if it gets the opportunity. If a squirrel gets bitten, it may not be affected. Adult rock squirrels have evolved the capacity to at least partially neutralize the venom. Even more remarkably, recent research indicates that rock squirrels may apply snake scent to their bodies to camouflage their own scent. This may be especially important in the young, who have not yet developed resistance to the snake’s deadly bite.
It is easy for us to misunderstand the rock squirrel as we stroll along the Riverside Walk, glimpsing only a brief moment in its daily drama of survival. The often harsh realities of life in Zion forces it to forage, hunt, raise babies, and defend itself and them from enemies—in a struggle often far removed from human view. We can help by respecting—and not interfering—with its skills and status as a wild creature.
The Secret Life of River Stones
Unlock the hidden geologic mysteries of river stones with Park Ranger Robin Hampton as she reads an article written by Park Ranger Barb Graves for the park's Nature Notes.
Hiking Wildcat Canyon to Right Fork of North Creek, my ranger friend, Jon, raises a finger to his lips signaling silence. Stopping abruptly, I scan the broad expanse of Navajo Sandstone, dotted with fist-sized iron concretions like a red-spotted toad’s raised nubs. Following Jon’s line of sight, I search for the anticipated animal: mountain lion, rare bird, perhaps bobcat? “If you’re very quiet and they think you aren’t looking,” whispers Jon, “you can see them moving around and hear them talking to each other.” Humored, I realize Jon’s mystery animal was not a rare species, but the abundant tribe of round iron concretions dotting the landscape before us. I could easily imagine them, carrying on in a bustle of activity until our human presence rendered them silent and still.
All stones, although not alive, are a foundation of life. Aldo Leopold wrote in A Sand County Almanac, “Land then, is not merely soil; it is a fountain of energy flowing through a circuit of soils, plants, and animals.” Stones lining Zion’s Virgin River remind me of this fountain of energy and the circuit of life created by their many minerals. Along the Virgin, point bars and shoreline deposits reveal stones ranging from tiny pebbles to bowling ball-sized cobbles. All these stones share some of life’s building blocks, mainly oxides and minerals, whose elements bond together in unique combinations.
Concretions form when water dissolves and precipitates minerals from Navajo Sandstone, coating the inner surface of air pockets, resulting in an iron marble impregnated in stone. Over time, less-resistant sandstone erodes, leaving a carpet of loose, round, dark nodules. Erosion transports many concretions and other loose stones down slopes, into tributaries, and, finally, on a ride down the Virgin River.
Stone combing, like beach combing, is a discovery tour where sandstones, conglomerates, limestones, and metamorphic rocks splash the riverbed with diverse color, pattern, and texture. Mineral compositions provide a glimpse of geologic, climatic, and life forces in action when each rock was deposited. Rambling the Virgin River at Big Bend, looking at the sea of stones, it’s easy to enter a hidden doorway to the past, like coming across a centuries-old photo album buried in the attic, and spending an afternoon immersed in lives of another time.
At Zion, another time is exactly what stones reveal. From the Mesozoic‘s 240-millionyear- old Moenkopi Formation to recent Cretaceous lava flows, Virgin River stones derive from a smorgasbord of paleoenvironments. I imagine the original setting of each stone; a wide shallow sea bustling with fossil oysters; a vast desert with hot sand fiercely blown; an oasis of tiny plants and massive dinosaurs on the verge of extinction; a forest of early evergreens destined for petrification; or lava, glowing red as steam jets hiss.
During creation of Zion’s Lava Point, vents and cinder cones spewed lava at more than 2,000 degrees Fahrenheit. Eroded downhill over thousands of years, most Virgin River lava stones look like black sponges—full of pits and holes—evidence of hot gases escaping as hot rock met cool air. Black lava rocks, more resistant to the river’s erosional forces than weaker sandstones, are abundant in the riverscape, even though the massive Navajo Sandstone far outweighs lava in the surrounding landscape.
When sandstone chunks enter the river-rock tumbler from overhanging cliffs, chemical and physical processes dissolve the glue— primarily iron oxide and calcium carbonate— that fill intersticies between sand grains. The river’s tumbling action smoothes jagged rocks to rounded stones. As stones wear, minerals are released, beginning again the cycle of creating soil, and the circuit of energy continues. If you stop along the Virgin’s stonescape and are silent a moment, you might hear particles of newly emerging soil giggling with joy.
A River Forever "Wild and Scenic"
Discover what makes the Virgin River Wild and Scenic in this story written and narrated by Park Ranger Robin Hampton.
Early morning winds move downstream with the river; its soothing sounds are swept along, too. Today is March 30, 2009. Creatures living in Zion National Park don’t mark the date, but continue to pursue their ancient callings of reproduction and foraging for food.
One of daylight’s first birds—the Say’s Phoebe—gracefully swoops and cries. It’s too early in the season to see the large crop of young lizards—Plateau and Desert Spiny—scoot on top of the sand only to stop and give us the eye. If we talk to them, they listen—at least their expressions and cocked heads make them appear to be interested in a reptilian conversation.
Lustrous leaves sprout from mature cottonwoods, and with the gaining onset of tent caterpillars, the tree’s annual cycle of defoliation and sap loss begins. Hundreds of prepubescent moths start out as black dots inside wide swathes of netted cocoons clipped in at their tips to keep them webbed inside. Before long, these black dots become bluegray flecked crawlers that drop to the ground, stunned and unsure. Zion’s spring crescendo, loud with song and slither and wandering wind, pays tribute to a talented maestro—the Virgin River.
For hundreds of thousands of years this river, with its short reach (154 miles long) and steep tumble (its elevation loss is about 8,000 feet from beginning to end), has given, unhindered, its power, cutting capacity, and gifts of niches and life zones. Historically many other rivers in the United States have not fared so well, particularly those in the East. The Cuyahoga River, which flows through Cleveland, Ohio, is the most infamous. A putrid Cuyahoga was a throwback to a time when people held an unenlightened belief that water could dilute any substance poured and thrown into it. Industrial garbage, raw sewage, and animal carcasses gutted Eastern waterways, so in June of 1969, the chemically saturated Cuyahoga caught fire for the tenth time in one hundred years. It was big news because, now, federal government agencies and the general public were more environmentally savvy. It was not acceptable to change water into poison. A literal flare ignited a flame of disgust among local and national communities. Out of the outrage, the Clean Water Act was born.
What the Virgin River has that the Eastern rivers don’t are out-of-the-way slot canyons. An inhospitable but stunning terrain means some places are so isolated that getting to them requires skills equal to that of a bighorn sheep. Canyoneering, rock climbing, and backcountry travel will bring the adventurer to the edge of gaping chasms into which clamor streams, waterfalls, and the beating heart of it all—the Virgin River.
On March 30, 2009, Zion National Park’s modest runlets and the Virgin River—165 miles in all were designated wild, scenic, and recreational. A decision of this magnitude reflects the remote, undeveloped, and partially accessible attributes of these waterways.
It also carries forward an attitude of concern for the future welfare of this country’s watersheds. Congress and President Lyndon Johnson signed into law the Wild and Scenic Rivers Act in 1968. That year 27 rivers were designated as wild and scenic. By 2008, more than 11,000 miles of 166 rivers in 38 states were so honored. This represents slightly more than one quarter of one percent of America’s waterways. Today’s new law expands the system by more than 50%; 252 rivers in the U.S. are now listed.
The Virgin River’s residents, however, won’t understand this piece of significant news. Beavers will continue to dwell in its banks. The spinedace, a native minnow, will flutter in its silty home. From dawn to gracious dawn, the park’s waters will rise and fall, a cadence of sweet eternal breath. We may all breathe easier now. Our treasured river, our flowing veins of life, are forever protected.
Did You Know?
The Zion National Park Shuttle System, which debuted in 2000, has restored tranquility to Zion Canyon.