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Published: March 20th 2012
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Day 7
U-Shaped valley cut by Bishop Creek After realizing that in this whirlwind return to school that I'll never catch my tail, I figured I might as well crank out this last entry now before it gets any later. We were without either power, electricity or both on days 7 and 8, and day 9 was the flight back which coincided with St. Patty's Day. So forgive the tardiness, but hopefully that line of excuses suffices one way or another. There is still plenty of geology to cover, so let's get to it!
Day 7: Our first stop was along a roadside carved through a U-shaped valley.... hint, hint. The lateral moraines rising up from Bishop Creek was the last piece of evidence we needed to certify that this was the result of glaciation (photo 1088). From there we followed the creek ("crick" as it is appropriately pronounced where I come from) down a little further until we could get an aerial view of the lower-lying basin. It was awesome to see the volcanic tableland we had seen earlier in the trip, Bishop's Tuff, from a different vantage point. We were able to get a better idea of the magnitude of the massive 6-day event that led
Day 7
Bishop Tuff - Volcanic Tableland to the discharging of 80% of the magma chamber that lied beneath. The normal faulting along the tuff was more evident as well (photo 1089). Also visible in this picture is the binding elements of the tuff; the White and Sierra Nevada Mountains. Very cool view, another amazing stop.
From there we moved on to Alabama Hills which were formed when the Sierras steeply rose causing a dramatic relief. and eventually mass wasting (landslides). These hills appear enigmatic because they lie in Owens Valley (a basin) but are distinctly tall. Another distinctive feature in the hills is the color differential between them and their protoliths still rising up around them. This contrast can be attributed to the chemical weathering taking place in the hills vice the physical weathering taking place in the Sierra Nevada. With their higher altitude, the Sierra are susceptible to having their exposed faces scoured away by glaciers, revealing a fresh granite outcropping. The lower lying Alabama Hills have faced approximately 90 million years of precipitation which accounts for their rusty, oxidized appearance (photo 1092). Another interesting geological find at this site was porphyritic (a name used to describe the texture on igneous rocks when there
Day 7
Varying sized phenocrysts in a porphyritic rock are phenocrysts of distinctly different sizes) rocks which are formed when crystals within the rock cool at different stages causing some to be larger than others (the longer it takes to cool, the larger the phenocrysts) (Photo 1091). Walking around the hills a bit more, we were in search of the arch that had presumably been weathered by wind, but it was just a cool spot to snap a photo (1094). The last feature I wanted to note was the interesting appearance of exfoliation joints. As I understand them(which by no means makes this gospel), they are another result of extensional and compressional stress causing the rock to peel like an onion. Evidence of this type of jointing could be found throughout the hills (photo 1094).
After that adventurous stop, it was onto the next one! So much geology, so little time…. We wanted to get a view of Owens Lake, which has a similar story to Mono Lake, but suffered a much more disastrous fate. Looking out over what used to be a huge lake, you can see rings of its previous (and geologically recent) levels. While the lake levels had experience a severe natural decline from the
Day 7
Alabama Hills more precipitous Pleistocene epoch (photo 1100), the cataclysmic blow was delivered by the city of LA who began diverting the feed streams for drinking water in 1913. This was approximately 30 years prior to the Mono Lake diversion, so by the time awareness had been raised concerning the future of the lake and lake levels; it was already too late (photo 1097). Another fun day was in the books and it was time to make it to our campsite for the night! We ended up meeting a group of Notre Dame geologists and geology students which was cool. I slept outside again, no tent, just in my queen sized air mattress under the desert sky peppered with stars! It was the best night of sleep I had all trip. It fueled up the tank just enough for one more day in the field!
Day 8 – Day 8 was a light day geologically because it required heavy travel, but we still made the best of it and saw quite a few more geological treasures! Our morning started at Mesquite Flat (not at 6am for sunrise as was originally proposed, but at a respectable hour of about 9) where we
Day 7
Wind eroded arch in Alabama/Poverty Hills saw a depositional sequence of Navajo sandstone which created some pretty spectacular sand dunes. For these dunes to appear it takes three things: a supply of sand, strong wind, and something to slow the wind down. The mountains surrounding Death Valley were the suppliers and Tucki Mountain was the inhibitor. With each windstorm, the sands shift. However, the dunes are trapped in place (most of this info is courtesy of the sign posted in front of the dunes) (Photo 1106). Some cool biological points from the dunes: we saw a baby scorpion and rattlesnake tracks (no photos on my roll, hopefully someone will donate!). My phone was able to get a great picture of the well-sorted, fine-grained sand which is indicative of being carried by the wind. Up close, you can see that the small volcanic clasts are slightly bigger because they are less dense. Because wind sorts by mass, they were able to be carried the same way the smaller, denser clasts were (photo 1109).
After the dunes, we headed to Mosaic Canyon which was definitely one of my favorite stops of the trip. There was a wide range of spectacular things to see, all with different stories.
Day 7
Owens Lake with man derived evaporation rings Walking up through the canyon our first sights were of the flashflood, alluvial deposits that had lithified into conglomerates (photo 1113). This gave us a preview of what likely laid ahead, a well-carved and fascinating canyon. While it was awfully difficult to capture the magnitude of the canyon, using people for scale at either end of the photo hopefully provided some idea (photo 1115). We were also able to put our hands on breccia, which are angular clasts that typically appear along faults (photo 1118). These clasts can break off and flow downstream, causing them to round and occasionally become part of the conglomerate sequence we saw near the base in the alluvial deposits. Another interesting feature the canyon allowed us to see were magnificent “Z” folds, which are exactly what they sound like, folds in the rock that look like “Z’s”. These occur when there is a squeezing pressure exerted on the rock coupled with flow or shear (photo 1119). On our way out, we encountered one last geologic treasure: reworked conglomerate beds. These were enormous clasts that were originally deposited horizontally and due to immense water flow during a flood were rolled onto their sides. Eventually, horizontal deposition
Day 7
Owens Lake level during Pleistocene (above the road, which is an escarpment above the lake). resumes leaving behind T-shaped layers in the rock bed (photo 1120).
Our final stop for the day, and sadly for the trip, was a view from on top of it all. The lookout is called Dante’s View, named after Dante Alighieri, and it is a 5500ft scenic overlook of Badwater Basin (which we had seen at base level a full week earlier). It was a great place to take a few deep breaths, think about everything we had done, and playfully toss some rocks (not big rocks, and not all the way down the canyon). A cool feature noticeable from this bird’s eye perch is the roads in the basin that seem to trace the alluvial fans coming out from the mountains (photo 1123).
We made it! A full 8 days with a bunch of personalities, some quiet, some larger than the sky, but all in all it was truly the trip of a lifetime that I couldn’t recommend any higher to future students at any level or background of interest. I ended up with a bunch of postcard-worthy pictures, pictures of knives, notebooks, pens, pencils, hands, and people (scale is important!), a bunch of new friends, and
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Mesquite Flat Dunes one huge helping of respect for our planet. Until this summer’s ocean bottom seismology adventure, signing off for now.
Cheers!
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