Joshua Tree National Park Lindsay Patrick Emily Howson Lizz Echard
Draw a line around the world, starting mid-center between Joshua Tree and Death Valley, and you will touch or come close to many of the world’s great deserts: Mojave, Great Basin, Sahara, Arabian, Iranian, Gobi. Most deserts occur between the latitudes of 15 and 40 degrees on either side of the equator.
For a first time visitor the desert only hints at it’s vitality and may appear uninviting or bleak; but surreal geologic features add to the attraction of this place.
One Of A Kind • Nearly 800,000 acres • Southern California • Is a land shaped by strong winds, sudden torrents of rain, and climatic extremes. • Rain Shadow desert • Junction of 3 ecosystems: • 2 deserts (mainly determined by elevation), & 1 oasis
1st Ecosystem • The Colorado Desert (a western extension of the vast Sonoran Desert) • “Low”: 3000 ft above • Eastern & Southern • Creosote bush, Spidery Ocotillo & “jumping” Cholla Cactus
2nd Ecosystem • Mojave Desert • “High” (cooler & wetter) • Northern part of park • Joshua Tree (Western part) • Lowest absolute elevation & the highest maximum temperature 134°F • “Basin and Range Province”: A landscape of alternating mt ranges & their bordering basins • Explorer John Fremont- “The most repulsive tree in the vegetable Kingdom”. • Rain Shadow effect • Created when mountains lie parallel to moist, coastal areas.
3rd Ecosystem • Oases: Dramatic compared to arid surroundings • Western • 4000 feet • 6 Fan Palm Oases • Water occurs naturally along fault lines • 80 to 90 years • 75 feet • Shaped like a fan and folded like an accordion • The presence of beetles is actually a sign of a healthy oasis.
The Geology of Joshua Tree National Park • “As old as the desert may look, it is but a temporary phenomenon in the incomprehensible time-scale of geology” –Ranger • plate tectonics, volcanism, mountain-building, & stark erosion. • 900-5000 ft above • Sand dunes, dry lakes, flat valleys, rugged mountains, granitic monoliths, and oases • Queen Valley & Lost Horse Valley • Pleasant Valley-basins • 6 Mt ranges • Little San Bernardino Mountains (southwestern) • Cottonwood • Hexie • Pinto Mountains (center) • Eagle & Coxcomb Mts (eastern)
Faults • Joshua Tree is crisscrossed with 100’s of faults • Can see raw rocks & effects of earthquakes. • San Andreas Fault on south side of park (Keys View) • Blue Cut Fault (center) • Fault zones = localized natural springs • Pinto Mountain fault (Maria Oasis-visitor center) plus 4 other fault oases
Rockpiles • 100 mil yrs ago, molten liquid, heated by the movement of Earth’s crust, oozed upward & cooled while still below the surface. • granitic rock called monzogranite. • system of rectangular joints • 1ST: Horizontal set, removal by erosion of overlying rock, called gneiss • 2ND: Vertical set, contact of the monzogranite with its surrounding rocks • 3RD: Vertical set, develop rectangular blocks. • Rock Piles= As ground water filtered down through the monzogranite’s joint fractures, transform soft clay, the eroded boulders settled one on top of another.
Daytime: Birds, lizards, roadrunners, & ground squirrels • Nocturnal: snakes, bighorn sheep, kangaroo rats, coyotes, & black-tailed jack rabbits. • Burrows • Reptiles vs. mammals in storing water • Desert Plants National Park: 700 species • Cryptobiotic crusts- hold the place in place
Wilderness is an area “…where the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain…”
Can see the Mexican border/ Mount San Jacinto/ Los Angeles from the mile-high Keys View. • Over 12 million ppl in LA= smog/pollution
Man-made lake 20 miles outside park, scientists claimed that it’s messing with the rain shadow effect.
Admired By Many • Clear skies & clean air • Peaceful and tranquil • An adventure • Extremely fragile, carelessness may leave lasting scars or disrupt a system of life that has existed for eons.
Resources • http://www.nps.gov/jotr/ • http://www.joshua.tree.national-park.com • http://www.desertusa.com/jtree/jtmain.html • Our Geology book under “Rain Shadow Deserts”
5 Questions • Where do oases occur? • What is the name for the granitic rock found in the rock piles at the park? • What famous fault is on the south side of the park? • Which of the two deserts (ecosystems) is considered the “low” desert? • Why is it a rain shadow desert?