February 2005 - President's Day Weekend
Canyonlands National Park, Utah
Due to our upcoming spring trip to Holland and Belgium, we wanted our house sitter and
our dogs to get used to one another again. Dogs are full of surprises– always scheming
and plotting. So we thought a three-day weekend with the house sitter would reveal any
mutinies or rebellions that they have been planning.
We picked up a rental car and left Broomfield by 3pm. Within 90 minutes, were passing through
the Eisenhower Tunnel beneath the continental divide. After wasting about twenty minutes looking
for an outlet store in Silverthorne that no longer exists, we were soon over Vail Pass and it
was all downhill to Utah. Heavy rain east of Grand Mesa slowed our progressive due to poor
visibility and we arrived in Moab at exactly 10 pm.
Dead Horse Point State Park
We left Moab about 10 am Saturday morning and drove north on US 191, then west on State
Highway 313. Our first stop was Dead Horse Point State Park, which is the unofficial
"little sister" of Canyonlands National Park. Like Canyonlands, Dead Horse Point offers
panoramic views of the Colorado River and its system of canyons. The park facilities,
including the visitor center, are considerably better than those at Canyonlands, which
are rather primitive. The entrance fee is $7 per vehicle.
Nineteenth century horse and cattle ranchers exploited the natural terrain of Dead Horse
Point to confine grazing livestock. The several square miles that constitute the modern-day
state park are on a promontory plateau that can only be accessed via a 60 ft-wide "neck"
of land. Bounded by steep cliffs at all other points, the ranchers required only a short
length of fence at this crucial point to prevent their animals from straying. Allegedly,
a herd of wild mustangs once strayed into the area and died of thirst because they became
confused and couldn't find their way out. This is how the area became known as Dead Horse
Point.
The finger of rock that is now the state park was formed by 150 million years of
sedimentation and erosion. The Colorado Plateau, which includes most of southeastern Utah,
has been uplifting for tens of millions of years. Uplift accelerates erosion, so as the
terrain rose, the Colorado River dug ever further downward. Where the river eroded directly
downward, precipitous cliffs were carved. Where the river migrated laterally as it eroded
downward, terraced canyons were etched.
The view from Dead Horse Point may be the most impressive in southeast Utah, although
Canyonlands Green River Overlook would be a close second. The centerpiece of the vista is
a spectacular tight and deeply entrenched meander of the Colorado River. The green water
and grassy banks of the Colorado contrast sharply with the vivid browns and reds, as well as
the more subtle oranges and purples, of the finely layered rocks that confine the river.
Upstream, toward the north, the Colorado is lined with a series of bright turquoise evaporation
ponds used to extract potash from the mineral-rich water. The La Sal Mountains form a
towering snow-capped backdrop to both canyon and river.
We spent a couple of hours exploring a series of overlooks scattered along a trail that
closely follows the canyon rim. It was extremely windy. In fact, the rule of the day seemed
to be - the better the view, the stronger the wind. In the distance, we could see rain showers
that seemed to be moving toward Canyonlands. So the race was on. Who would get there first, us
or the rain?
Canyonlands
When we stopped at the Canyonlands visitor center to pay our $10 entrance fee, the ranger cautioned
that the weather forecast indicated an 80% probability of precipitation. The storms were definitely
heading our way. It was very tempting to stop at every overlook along the highway, but we wanted to
reach the Mesa Arch trailhead before it began to rain or snow.
Although neither as vast nor as rugged as the Grand Canyon, Canyonlands is more colorful than its
downstream sister. Minute variations in mineral content can produce substantial differences in color.
The rocks of Canyonlands, as well as Dead Horse Point, are also considerably younger than those of
the Grand Canyon and represent a different period of earth evolution. Both national parks offer
vistas that overwhelm with sheer vastness.
The rain began just as we reached the parking lot for the Mesa Arch trail. Fortunately, it was only
a misting drizzle and it was not going to stop us from seeing the arch, which was only a short distance
away. At ½ mile round-trip, it is one of the least strenuous trails in the park. While not the focus
of the trail, the slickrock path offers a representative sampling of the plant-life that exists in the
desert of southern Utah. After ten minutes of winding our way through Pinyon Pine, Utah Juniper, Yucca,
Mormon Tea, and Prickly Pear Cacti, we spotted the end of the plateau and the arch perched on its edge.
Despite the intermittent drizzle, Mesa Arch offered some great views. Whenever I took my camera out,
it began to rain harder. Whenever I put the camera away, it began to dry out. Another rule of the day
seemed to be that the rain starts when you take your camera out of the bag.
Mesa Arch is a buff-colored formation in Navajo Sandstone perched at the edge of a sheer 1400 ft cliff.
Below a series of smaller cliffs lead to the Colorado River, nearly ½ mile lower than the spot on
which we were standing. The margins of the lower canyons are studded with towers and pinnacles, even a
few arches can be spotted if one knows where to look.
The arch consists of middle-Jurassic Navajo Sandstone, the youngest of all Canyonlands rock formations.
More recent deposits, such as the Entrada and Carmel Sandstones, which dominate parts of nearby Arches
National Park, are missing in Canyonlands because the west side of the Moab Fault has experienced
considerable uplift. The younger rock formations were a casualty of the accelerated erosion induced by
this uplift.
Green River and Grand View Point Overlooks
Next stop was the Green River Overlook, which offers one of the classic views of the American Southwest.
If asked to summarize their impression with a single word, most people standing at the Green River Overlook
would choose adjectives like "stunning", "beautiful", or "vast." My word would be "geology." There are few
places on Earth where a comparable span of geologic history is revealed unobscured by vegetation. The overlook
is poised on the Kayenta formation, which forms a resistant cap to the cliff-forming Wingate sandstone. Both
date from the early Jurassic, the period when dinosaurs began to roam the planet in great numbers. The deeper
the formation, the more ancient the rock. At the base of the Wingate cliffs is the gently-sloping late-Triassic
Chinle formation, a colorful and poorly consolidated layer best known for its occurrence in northeastern Arizona
where it forms the Painted Desert. As this softer layer is eroded from beneath the Wingate, entire columns of
the overlying formation collapse forming shear vertical cliffs.
Below the Chinle is a fairly resistant layer of sandstone known as the White Rim Formation. Because this 250
million year-old layer, which predates the emergence of the dinosaurs, is somewhat impervious to erosion, it
forms a relatively featureless plain immediately below the Wingate cliffs. Only in the immediate vicinity of
the river, and its major tributaries, has this layer been breached by erosion. Beneath the cap-forming White
Rim Sandstone is the much softer and easily eroded Cutler Formation.
If first visited this overlook more than twenty years earlier as a twenty-something graduate student in Earth
and Planetary Science. It has been developed considerably since that time. The road is fully paved and
attractive stone and wood railings have been installed. Since that first visit, I have returned every five
years or so and the view never fails to rekindle my fascination with geology.
A few miles from the Green River Overlook, the Grand View Overlook features a more rugged dissection of geologic
strata. Erosion has been more aggressive in this area and the protective White Rim Sandstone has been breached
in numerous places, exposing the more vulnerable Cutler Formation to extensive modification and creating a
complex system of canyons known as Monument Basin due to the ubiquitous 300 ft-high mesas, towers and pinnacles
that fade into the distance.
Canyonlands - Day 2
Canyonlands National Park consists of three administrative districts. This entire trip would be focused on the
northernmost of these sections known as the Island in the Sky district. The name refers to the high peninsular
mesa that rises above the confluence of the Colorado and Green Rivers nearly ½ vertical mile below. This
region of the park has three major localities of interest, the Mesa Arch/Green River Overlook and the Grand View
Point areas, both of which we visited the previous day, and the Upheaval Dome area, which was our goal for this
day.
A two-mile round-trip trail traverses the outer elevated portions of the dome and culminates in a series of
observation points that provide comprehensive views into the central depression of the dome. Even in the absence
of this curious structure as a focal point, the hike is scenic and interesting.
Geologically, Upheaval Dome is, at minimum, an anomaly and possibly a mystery. The rigorously ordered layers of
rock that characterize so much of southeastern Utah are deformed and disrupted here. Within a three-mile diameter,
rock has been bent upward forming a series of concentric rings. Each ring represents a distinct geologic layer.
Older layers are toward the center and younger layers are toward the periphery. It almost seems if a huge bubble
rose to the surface, disrupting the surface of the Earth in the process.
One explanation of the structure, the Salt Dome Theory, envisions exactly such a mechanism. A massive salt diapir
from the underlying Paradox Evaporite Formation buoyantly rose to the surface, pushing the intervening rock layers
vertically and laterally aside in the process. An alternative explanation is the Impact Crater Theory, which is
based on the observation that the geologic structure of Upheaval Dome resembles that observed at impact craters
throughout the Solar System.
I find the impact theory most compelling for two reasons. First, the excavation of surface layers associated with
an impact could induce a subsequent upward flow of the underlying salt layer in response to overburden reduction.
So with an impact trigger, the two theories can become mutually reinforcing. Second, if Upheaval Dome is a product
of upward salt flow alone, such features would be expected to be common throughout southeastern Utah, extensive
portions of which are underlain by the Paradox Salt Formation. Yet Upheaval Dome is clearly an anomaly.
As we were leaving the park, we made one last stop at the Shafer Trail Overlook near the park boundary. In
contrast to the vistas offered at Green River and Grand View Point Overlooks, the Shafer Trail view offers a
more detailed peek down a single canyon. The landscape is strikingly reminiscent of the Grand Canyon, with
its rapidly alternative sections of gently-sloping terraced layers and vertical cliffs. In this case,
however, the eye is not drawn to the rock itself, but, rather, what has been built into the rock– a
dirt road that perilously descends the canyon wall via a series of tight switchbacks over a loosely
consolidated sediment debris fan. Originally a cattle trail, the path was modified to a jeep road during
the uranium mining era. The road simultaneously instills a sense of vertigo and fascination. I have often
wondered what it would be like to drive down this road and if I would have the nerve to do so myself.
One day I may rent a jeep and try. But not this trip.
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