Week 7 - Death Valley

Ubehebe Crater, Credit: W.R. Jones, NPS.

At the Ubehebe Crater stop a photo from the image gallery shows the walls of the crater, where the eruptions that caused the maar exposed older layers. Searing basaltic magma ascended, following weaknesses in the Earth’s crust. As the magma flowed through the fault-weakened rock, it encountered water-logged bedrock and alluvial fan sediments, causing immense amounts of steam that exploded away the confining rock as the steam powered energy released. This is the youngest and largest crater created in the volcanic field (Frank, 2016). This leads me to wonder, how old these rocks really are. To find out, I would begin with the principle of superposition, since the blast revealed layers of rock. Then, I would observe any folds or inclines to establish if there were any crustal disturbances following their deposition. I would also observe any unconformities and any fossils that could tell me more about the age of the rocks. I would also use correlation to detect any matches of rocks from other areas. Radiometric dating could assist in dating the layers, however, with the ash, I would need to relate the strata to datable igneous masses (Lutgens , 2016, pp. 471-485). In fact, recent studies of the rocks from the Ubehebe Crater have revealed that the crater is much younger than originally thought, presenting a higher volcanic hazard as well (Thornhill, 2012).

Sliding Rocks, Credit: Marli Miller

At the Racetrack Playa stop a photo from the image gallery shows what appears to be sliding rocks. Racetrack Playa is nestled between the Last Chance Range to the west and Cottonwood Mountains to the east. It is an almost seamlessly flat dry lake that collects rain during periods of heavy rain and forms a shallow temporary lake. Since the surface is level, sliding rocks in the area have puzzled geologists for ages. The movement creates a grooved pathway; however, no one has ever observed these rocks sliding. This leads me to question how this movement is possible. To answer the question, I would test the surrounding environment, wind factors, and tilt of the surface if any. I would measure the rocks involved in sliding, the trails left behind, and direction of travel. I would also measure rocks in the area that have not moved and compare them to the ones that have. I would observe at least two rotations of wet and dry conditions when the lake floods and dries out. I would map out all of the “sliding rocks” to see if any patterns emerge (Frank, 2012).

Split Cinder Cone, Credit: Tom Bean, NPS

At the Split Cinder Cone stop a photo from the image gallery shows a once complete cone, now split in two. This cone was created by basaltic lava using fault-weakened rock. The cone split from movement of the fault zone, ripping the crust into two separate elements. This makes me wonder the speed in which the fault line is moving. To measure this, I would take measurements every month for one year and calculate the gap measurements for each month. I could use radiometric dating to date the rocks in the area. Once the age of a feature cut by a fault is known, and the distance the two parts have moved, the rate can be calculated (Frank, 2012).

References

Frank, D. (2016). Death valley geology field trip: Racetrack Playa. United States Geological Survey. Retrieved from https://www.nature.nps.gov/geology/usgsnps/deva/ftrac1.html

Frank, D. (2016). Death valley geology field trip: Split Cinder Cone. United States Geological Survey. Retrieved from https://www.nature.nps.gov/geology/usgsnps/deva/ftcin1.html

Frank, D. (2016). Death valley geology field trip: Ubehebe Crater. United States Geological Survey. Retrieved from https://www.nature.nps.gov/geology/usgsnps/deva/ftube1.html

Lutgens, F. K, Tarbuck, E. J., & Tasa, D. (2016). Essentials of geology. (13th ed.). Upper Saddle River, NJ: Prentice Hall (Pearson). ISBN-10: 0134446623; ISBN-13: 9780134446622

Thornhill, T. (2012). As if Death Valley wasn't dangerous enough... geologists discover that one of its volcanoes is due to go off. Daily Mail. Retrieved from http://www.dailymail.co.uk/sciencetech/article-2091130/Death-Valleys-Ubehebe-volcano-say-Columbia-University-researchers.html