We spent a wonderful day re-visiting Joshua Tree National Park. We were here 10 years ago. And yet, we saw the park again as if through new eyes, discovering more fascinating facts and details. No matter how often one visits wilderness areas, there is always something new and different to marvel over and appreciate.
Joshua Tree National Park spans two
types of deserts: the Colorado Desert in the south (below 3,000 feet
elevation), and the southern boundary of the Mojave Desert in the western
section of the park (above 3,000 feet elevation). The difference in elevation
creates more variety in ecosystems and plant vegetation, all found in this one
park. The Joshua Trees, after which the park is named, grow primarily in
the larger western area of the park.
We entered the park from
the south along the Pinto Basin Road which takes you through the lower and hotter Colorado
Desert, an extension of the much larger Sonoran Desert that spans southern
Arizona and northwest Mexico. Here creosote bushes dominate the landscape, as
well as palo verde trees, and ocotillo and cholla cactus.
Washes cut across the
landscape, conduits for rushing water when the rains eventually materialize.
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| the Pinto Basin Road through the south of the park |
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| creosote bushes dominate the terrain, reproducing by vegetative cloning - some clones are estimated to be over 9,000 years old, which makes them the Earth's oldest living organism |
We stopped to look at
the Ocotillo patch and then further along we walked the quarter-mile loop through the Cholla Cactus
Garden.
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| the thorny ocotillo is not a cactus but a deciduous shrub that is rain dependent and sheds leaves up to five times a year |
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| cholla cactus, also known as the teddy-bear cactus |
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| close-up of the cholla cactus, definitely not a cuddly teddy-bear |
Beyond the Cholla Cactus
Garden, the desert transitions to the higher, cooler Mojave Desert. Here we began to see the striking boulder
stacks, Pinyon Pines, Mojave Yuccas, prickly pear cacti, and Joshua Trees.
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| boulder stacks, Yucca cacti and more creosote bushes |
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| The inside of a Joshua tree is fibrous and has no annual growth rings, so scientists estimate their age by dividing the tree's height by the annual average growth rate of 1.5 inches. The typical life-span of a Joshua tree is 150 years, and the oldest trees in the park range from 20 to 45 feet in height |
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| the iconic boulders and rock formations that define the park landscape |
The highlight of today’s
visit was exploring the Geology Tour Road, an 18-mile loop. Recommended for 4-wheel drives, the
road takes you through some fascinating geology. This region sits atop two plates and several active faults, and the landscape we see today is the result of two
episodes of mountain building along the fault lines. The latest of these episodes was followed by
uplift and deep erosion, and then by further uneven uplift along faults.
Erosion exposed two rock bodies originally formed below the Earth’s surface:
the 1.7-billion-year-old Pinto gneiss and the 85-million-year-old monzogranite,
which forced its way into the gneiss as molten magma. The magma cooled at a depth of about 15 miles
below the surface and crystallized to form solid rock, monzogranite. Erosion has stripped the overlying Pinto
gneiss to reveal the interesting monolith outcrops we see today, and which also
attract rock climbers from all over.
From Keys View, we looked out over the Coachella Valley, home to Indio and Palm Springs. Across to the west lies Mt Jacinto, the highest peak, and to the south we could see the Salton Sea. This is the area where the Pacific Plate meets the North American Plate, and the San Andreas Fault is visible as a ridge marking the boundary between the fault lines.
Here is where the northbound North American Plate and southbound Pacific Plate grind past one another at an average rate of just under two inches per year. This would imply that in the past ten years since we last stood at Keys View observing the San Andreas Fault, the plates have moved almost 20 inches past one another.
Our final stop for the day was at Hidden Valley where we walked the one-mile loop through a rock-enclosed valley. Here is where cattle rustlers apparently hid their illicit herds. In the fading sunlight, the rocks looked fantastic and other-wordly. Eventually we noticed several climbers on a couple of the larger outcrops. They looked like specks against the gigantic rock face.
Here are a few more memorable captures of granite boulders and Joshua trees:
We came out at the northern end of the park, at Twenty Nine Palms, and headed back to Indio along the Twenty Nine Palms highway and route 10.
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| stopped to have lunch overlooking Pleasant Valley, gazing at the results of billions of years of geologic processes in front of us: Pleasant Valley is the result of faulting and consequent uplift and downdrop; the twin peaks of Malapai Hill, rising 400 ft above the valley floor and likely formed within the last 2 to 3 million years; the two-colored hills to the right are an excellent representation of the ancient Pinto gneiss, the oldest rock in the park at about 1.7 billion years, and the pink exposed monzogranite that remains as the fascinating boulders we see today |
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| the long ridge under the bank of clouds is the San Andreas Fault |
Here is where the northbound North American Plate and southbound Pacific Plate grind past one another at an average rate of just under two inches per year. This would imply that in the past ten years since we last stood at Keys View observing the San Andreas Fault, the plates have moved almost 20 inches past one another.
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| the many fault lines that crisscross through Joshua Tree NP |
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| where is the rock climber..... |
Here are a few more memorable captures of granite boulders and Joshua trees:
We came out at the northern end of the park, at Twenty Nine Palms, and headed back to Indio along the Twenty Nine Palms highway and route 10.