• Joshua Tree is a beautifulnational park and a gem forgeological observation andappreciation.• The park is located in southernCalifornia.• Two large desert ecosystemscomprise the landscape of thepark – the Colorado Desert(part of the Sonoran Desert)and the Mojave Desert (“ADesert Park”, 2013).
• The landscape we see around the park today is the resultof two widely separated periods of mountain building.The most recent occurrence caused uplift and deeperosion, which was then followed by more uneven upliftnear faults.• Due to erosion, we are left with the amazing rockformations that we see today in Joshua Tree NationalPark, the remnants of ancient mountains (Biringer, 2005).
Metamorphic - Gneiss• 1.5 billion-year-old Pintogneiss• Formed from sedimentary andigneous rocks that were burieddeep long ago and underwenta chemical change to arrive atits present state (Biringer,2005)• Oldest rocks in Joshua TreeNational Park, dating from thePrecambrian• Pinto gneiss is primarily madeup of quartz, feldspar, andbiotite (“Rock Types”, 2011).
• A type of granitic rock, which ismade up of quartz, mica, andfeldspar (Buscher, 2011)• 150 million years old• Monzogranite was an intrusionof the much older gneiss in thepark. At a depth of 15 milesbelow Earth’s surface, themagma cooled and began tocrystalize and form into solidrock.• Millions of years of erosion haveweathered away much of thegneiss that these rocks onceintruded, leaving themonzogranite exposed as wesee it today (Biringer, 2005).Igneous - Monzogranite
• The monzogranite’s fracturesallowed ground water to seepthrough, softening some of thegrains. This constant moving watergave the rocks their characteristicroundness.• Before Joshua Tree National Parkwas a desert environment, flashfloods eroded away the groundsurface and gneiss, exposing themonzogranite and allowing thehuge rectangular boulders to settleon top of one another and leavingus with the impressive formationsof the present (“GeologicFormations”, 2013).Igneous - Monzogranite
• Genus opuntia; family cactacea• Thrives in the hot desert of the American Southwest• Grows in very dry, rocky soil (“Cholla Cactus”, 2013)• Grows to a height of 3-5 feet (“Teddy Bear Cholla”, 2010)• Develops in desert valleys between 100 and 2000 feetelevation• Also known as jumping cholla for the way the cactus is able toreproduce. The fruits of the teddy bear cholla are sterile, andthe plant relies on fallen stems to grow new cacti. The spinesof the teddy bear cholla separate easily from the cactus andcatch a ride on any animal or person that is unlucky enough toget that close. The stems are said to “jump” onto passersby asa means to spread out and multiply (Kuchan, 2012).
• As plants lose a lot of water through theirleaves, desert plants had to adapt to thearid environment by slowing this waterloss.• Leaves became smaller and smaller asthe cacti evolved, eventually formingsharp points, and finally arriving at thespines that currently adorn the cacti,which are resistant to the harshenvironment and allow better waterretention.• The spines have evolved to provide morethan just water retention. The sharpspines provide protection from animals.They also are handy for catching ontoanimals to get a free ride to a new placeto take root. The numerous spines createtheir own shade and deliver protectionfrom the sun (Saunders, 2009).
• Family phrynosomatidae• Grow 6 to 9 ¼ inches long• Found predominantly in California• Males often have distinguishing blue marks, specifically on thethroat or belly (“Western Fence Lizard”, 2007), while femalesand young lizards lack this coloration. Some are all black.• Diet consists of insects and spiders.• Commonly referred to as a spiny lizard due to theiroverlapping, pointed scales (“Sceloporus Occidentalis”, 2013).• The lizards like to settle on rock outcroppings, rocky slopes,cliff faces, and forested areas (“Western Fence Lizard”, 2012).
• Reptiles and amphibians came froma group of organisms calledterrestrial vertebrates.• Reptiles split from amphibians into agroup called Amniota about 350million years ago.• It was through the development ofthe amniotic egg that lizards wereable to adapt to the rigors of living onland (Ivanyi, 2004).• An important evolutionarydevelopment that some lizards haveacquired, including the great basinfence lizard, is that of autotomy, orthe ability to detach the tail. This self-amputation is done as a means ofprotection and the tail will slowlyregenerate (“Western Fence Lizard”,2012).
Above: sign posted at the San Andreas Fault Zone in Joshua Tree National Park
• The San Andreas Fault represents the meeting of two ofearth’s constantly moving plates. It is the boundary betweenthe Pacific Plate (to the west) and the North American Plate (tothe east).• The Pacific Plate moves in a northward direction, which is thecause of earthquakes along this fault.• The fault is more than 800 miles in length and goes as deepas ten miles into the earth.• Visually, the presence of the fault can be seen on the surfaceby a linear trough over most of its length (Schulz, 2013).
• Came into existence15-20 million yearsago.• Comparing thegeography along thefault, scientists believethat the totalaccumulateddisplacement since itsexistence is at least350 miles, with a driftrate of approximately 2inches per year(Schulz, 2013).
• The southern segment of the San Andreas Fault is thepart that can be seen from Joshua Tree National Park. Itextends from the Cajon Pass to the Salton Sea, 186miles.• This part of the fault has documented aseismic creep.• As for the future of activity along the San Andreas Fault,the southern segment is long overdue for an earthquake,as it has not ruptured since prior to 1700. It is projectedthat the next big earthquake will be approximatelymagnitude 8 (Alden, 2013).
• "A Desert Park." U.S. Department of Interior National Park Service, 1 May2013. Web. 19 May 2013.<http://www.nps.gov/jotr/planyourvisit/desertpark.htm>.• Alden, Andrew. "All About the San Andreas Fault." About.com, 2013. Web.19 May 2013. <http://geology.about.com/od/geology-ca/tp/aboutsaf.htm>.• Biringer, Brad. "A Geological History of Joshua Tree National Park." N.p.,2005. Web. 19 May 2013.<http://joshuatreenationalpark.net/history.htm>.• Buscher, Linda, and Dr. Dick Buscher. "Desert Green: Joshua Tree NationalPark." LiveScience, 3 June 2011. Web. 19 May 2013.<http://www.livescience.com/30488-joshua-tree-national-park-images.html>.• "Cholla Cactus." DesertUSA.com, 2013. Web. 19 May 2013.<http://www.desertusa.com/mag99/may/papr/chollas.html>.• "Geologic Formations." N.p., 1 May 2013. Web. 19 May 2013.<http://www.nps.gov/jotr/naturescience/geologicformations.htm>.
• Ivanyi, Craig. "Life as a Lizard Unit: An Introduction to Lizards." Tree of LifeProject, 2004. Web. 19 May 2013.<http://tolweb.org/treehouses/?treehouse_id=3686>.• Kuchan, Ryan. "Cactus Types - What is Jumping Cholla?." Cactus Facts.N.p., 9 Mar. 2012. Web. 19 May 2013.<http://cactusfacts.com/cactus/cactus-types-what-is-jumping-cholla>.• "Rock Types." Geology of the Joshua Tree National Monument. CaliforniaDivision of Mines and Geology, 5 Sept. 2011. Web. 19 May 2013.<http://www.nps.gov/history/history/online_books/geology/publications/state/ca/cdmg-cg-37-4/sec2.htm>.• Saunders, James. "Darwin and the Cactus." Chihuahuan Desert NatureCenter, 19 Feb. 2009. Web. 19 May 2013.<http://cdri.org/publications/nature-notes/evolution-ecology/darwin-and-the-cactus/>.• "Sceloporus Occidentalis." Idaho Museum of Natural History, 2013. Web. 19May 2013.<http://imnh.isu.edu/digitalatlas/bio/reptile/lacer/scoc/scocfram.htm>.
• Schulz, Sandra S., and Robert E. Wallace. "The San Andreas Fault." U.S.Department of the Interior, 11 Jan. 2013. Web. 19 May 2013.<http://pubs.usgs.gov/gip/earthq3/safaultgip.html>.• "Teddy Bear Cholla, Jumping Cholla." The Living Desert, 2010. Web. 19 May2013.<http://www.livingdesert.org/desert_plants_page.html?name=Teddy+Bear+Cholla%2C+jumping+cholla>.• "Western Fence Lizard." eNature.com, 2007. Web. 19 May 2013.<http://www.enature.com/fieldguides/detail.asp?recnum=AR0076>.• "Western Fence Lizard." N.p., 7 Nov. 2012. Web. 19 May 2013.<http://blm.gov.id/st/en/environmental_education/BLM-Idaho_nature/wildlife/reptiles/turtles_and_lizards/western_fence_lizard.html>.