Lindsay PatrickEmily Howson

Lizz Echard

•Draw a line around the world, Draw a line around the world, starting mid-center between starting mid-center between Joshua Tree and Death Valley, Joshua Tree and Death Valley, and you will touch or come close and you will touch or come close to many of the world’s great to many of the world’s great deserts: Mojave, Great Basin, deserts: Mojave, Great Basin, Sahara, Arabian, Iranian, Gobi. Sahara, Arabian, Iranian, Gobi. Most deserts occur between the Most deserts occur between the latitudes of latitudes of 15 and 40 degrees15 and 40 degrees on either side of the equator. on either side of the equator.

•For a first time visitor the desert only hints For a first time visitor the desert only hints at it’s vitality and may appear uninviting at it’s vitality and may appear uninviting or bleak; but surreal geologic features add or bleak; but surreal geologic features add to the attraction of this place.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

– The Colorado Desert (The Colorado Desert (a western a western extension of the vast Sonoran extension of the vast Sonoran Desert)Desert)

– ““Low”: 3000 ft aboveLow”: 3000 ft above– Eastern & Southern Eastern & Southern – Creosote bush, Spidery Ocotillo Creosote bush, Spidery Ocotillo

& “jumping” Cholla Cactus& “jumping” Cholla Cactus

• 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.

– 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.

• “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)

o Joshua Tree is crisscrossed with 100’s of faultso Can see raw rocks & effects of earthquakes. o San Andreas Fault on south side of park

(Keys View)o Blue Cut Fault (center) o Fault zones = localized natural springso Pinto Mountain fault (Maria Oasis-visitor

center) plus 4 other fault oases

• 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 Wilderness is an area “…where the earth and its community of the earth and its community of life are untrammeled by man, life are untrammeled by man, where man himself is a visitor where man himself is a visitor who does not remain…”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 Man-made lake 20 miles outside park, scientists outside park, scientists claimed that it’s claimed that it’s messing with the rain messing with the rain shadow effect.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.

• 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”

• 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?