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Cross-country hike to summit of Monument Mountain in Joshua Tree National Park, and some of the oldest rocks in California Trip Stats: (from Pinkham Canyon Road approach)
 Near Pinkham Canyon Road looking east, Joshua Tree National Park "Mind expanding" is what designer Jonathan Adler calls Joshua Tree. For those who have traveled deserts in Southern California, hiked the dry washes, climbed rust-red and brown rocks and seen valleys that extend nearly to the horizon backed by mountain ranges, Joshua Tree is a special place. It's an expansive wonderland of sublime beauty. It was our long-time friend Scott's idea to summit Monument Mountain in southern Joshua Tree National Park around New Year's Eve 2017. Scott has hiked many peaks on the Desert Peaks Section Peak List, and he has tons of experience hiking cross country. The views from the mountain's south ridge are incredible, and about 1/2 way to the summit, if you turn around and look to the southwest, you can see the Salton Sea, a large lake formed from overflow of the Colorado river when engineers in 1905 were attempting to deliver more water to irrigation canals . The weather was perfect: sunny, no wind, and 70 degrees. Fred and I had arrived from Boise for our yearly desert holiday fix. We piled out of Scott's red pick-up 5 miles down Pinkham Canyon Road and stood in a sun-flooded broad valley of yucca, cholla and creosote surrounded by mountain ranges on all sides. Looking north to our destination, we could see our ridge to the summit, but Monument Mountain was not in view. We started walking across the wash to the north.  Hike route to summit of Monument Mountain from Pinkham Canyon Road (black dashed line), Joshua Tree NP (North at top of map)  From edge of wash, climb up first hill to the south ridge of Monument Mountain As you look north, you see a rise and it is best to get to the top of it and onto the ridge that will take you to the top of Monument Mountain. The trail on top of the ridge is faint and marked at somewhat regular intervals with small cairns. Once on the ridge, the route is a gentle rolling climb to the summit cone of rocks with washes on both sides. Some dry washes have deep rock cuts at the top.  Fred ascending to ridge from Pinkham Canyon Road in valley below  Looking at Monument Mountain summit About 2/3 of hike distance, Monument Mountain finally comes into view. You can see faint trail leading up to the ridge after descending slightly down from the ridge into a broad sloping valley on your left and a saddle to your right. The climb up the stable metamorphic rocks to the summit is relatively easy.  Monument Mountain summit - 4, 834 feet  Augen gneiss at summit of Monument Mountain, some of the oldest rocks in California, age 1.65 bya (billion years ago)  Upon reaching the summit, we were somewhat surprised to see 2 people from the San Francisco Bay area that had hiked up via Porcupine Wash. When I exclaimed, "There's the red can!", one of them commented that it was just trash left on a mountain. I explained to him that it was a summit register, whereupon he signed his name. I told him that the register at Cowboy Camp in the Santa Rosa Mountains still had the entry I had written almost 20 years ago! Mt. San Jacinto, the towering presence over Palm Springs can be seen to the west. The rock at the summit looks and feels old because it IS old! These rocks record the earliest geologic events in Joshua Tree National Park - originated as sedimentary and igneous rocks that underwent metamorphism and then a couple of continent-building episodes finally to be uplifted during the Mesozoic tectonic events where it became fragmented. There are 4 units of this metamorphic complex within Joshua Tree. The augen gneiss on Monument Mountain is a metamorphic granite containing elliptically-shaped feldspar porphyroclasts in its layering (augen in German means "eye"). You can see these lighter grains of feldspar embedded in the dark rock. This type of rock has undergone Uranium-Lead geochronology from the zircon grains it contains to arrive at a date of 1.65 billion years ago, making these some of the oldest-known rocks in California.  Scott, Sue and Fred on summit of Monument Mountain  View to the southwest of the Salton Sea from the summit  Scott next to summit register, Eagle Mountains in the distance  Heading down The way down is straightforward - follow the ridge! This is a good first-time cross country hike for the hiker that wants to get off a well-trodden path and do some fairly easy navigation with a good topo map. There's a smaller ridge to the right (southwest) as you head down and we took it for a little while about 1/2 mile down, but then got back on the main ridge. Once we finally found the truck on Pinkham Canyon Road, we savored the setting sun illuminating the cholla cactus making them glow among the yucca and creosote.  References:
Kaiser, J. 2017. How Geology formed Joshua Tree National Park. Retrieved from https://jameskaiser.com/joshua-tree-guide/geology/ Powell, Robert E. 2001. Geologic Map And Digital Database of the Porcupine Wash 7.5 minute quadrangle, Riverside County, California, U.S. Geological Survey Open-file Report 01-030, scale 1:24,000, U.S. Dept. of the Interior, U.S. Geological Survey. Trent, D.D. 1998. Geology of Joshua Tree National Park, from California Geology, Dept. of Conservation, Divsion of Mines and Geology.
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About this blogExploration documentaries
– "explorumentaries" list trip stats and highlights of each hike or bike ride, often with some interesting history or geology. Years ago, I wrote these for friends and family to let them know what my husband, Fred and I were up to on weekends, and also to showcase the incredible land of the west. I hope to hear about your adventures! 
Happy Autumn!
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