The Mojave Desert is situated on the Western edge of Arizona, and is generally regarded as an extension of the Sonoran Desert, or the Great Basin to the North. However, its distinctly individual climate and ecology make it a completely seperate desert altogether. Its borders encompass more than (25,000 square miles) from the Sierra Nevada range in the North-West; Colorado Plateau in the East; San Gabriel-San Bernardino ranges in the South-West. Along the Great Basin border lies Death Valley National Park, North America's lowest point.
The topography of the Mojave is typical mountain-basin, with deposits of iron, silver, gold, and tungsten worked in the mountains, and extractions of potash, borax, and salt from the salt flats to which the basins drain. Usual Mojave climate is for fluctuating daily temperatures; hot, dry, and windy during the summer; often freezing temperatures during winter. Annual rainfall is less than 130 mm, primarily during winter - there is almost no precipitation to ease the arid summer.
Mojave flora is what characterizes it as being a desert in its own right, with over 200 unique species not even found in the adjacent Sonoran or Great Basin. Most prominent of these is the Joshua Tree, found in the southern reaches. The high-elevation Desert Spanish Bayonet and the Mojave Yucca are other yucca featuring majorly in the Mojave ecology.
The Joshua Tree (yucca brevifolia) is the largest of the yucca plants, and is found only in the Mojave Desert at altitudes of 600-2,000m. It is thought that the plant was named by early Mormon settlers, who thought of it as a likeness to the Christian prophet Joshua, waving the people on to the promised lands with upraised arms. Often growing in forest-like groves, the Joshua Tree has a preference for dry soils, largely on plains but also on mesa slopes. Despite growing to a height of 5-13m, and a girth of up to a meter, the 'Tree' is a misnomer, with the fibrous stems being covered by a layer of dead leaf remains. After flowering, each flower point dies off, and a new point grows as a branch below, so as the plant ages it progressively becomes more branched. With a life-span of 200 years or more, a Joshua Tree may definitely earn by appearance it's 'tree' suffix.