About 5 million years ago, the Sea of Cortez, the body of water that separates the peninsula from mainland Mexico, did not exist, and the land mass of today's peninsula was firmly attached to the mainland. However, a giant fault had formed in the earth's crust. Running roughly northwest/southeast, it joined the famous San Andreas Fault, which runs north across Alta (our) California. Driven by tectonic forces still not fully understood, the land mass west of the fault split off from the mainland. Moving at a rate of about 0.25 inch per year, the southern tip of the new peninsula left the mainland at the approximate location of today's Puerto Vallarta, and by about 3 million years ago, Baja was a well defined peninsula and the Cortez a prominent body of water.

Baja Sur as taken by astronaut L. Gordon Cooper from the Gemini 5 spacecraft
Photo Courtesy NASA
Today, at 800 miles long, Baja is one of the longest peninsulas in the world, exceeded only by the Malay, Antarctic, and Kamchatka peninsulas. The peninsula is also very narrow, averaging less than 70 miles in width, the narrowest part being the 26 miles from the western shore of the bay near La Paz to the Pacific, and the greatest being 144 miles at the latitude of Guerrero Negro. From the perspective of an astronaut, Baja is thus one of the most striking geological features on earth. Land area is 55,634 square miles, and the shoreline on both coasts totals 1,980 miles, excluding the interiors of enclosed bays.

Baja's mountains are not exceptionally tall, the double peak called Picacho del Diablo (Devil's Peak), the highest, being only 10,154 feet and 10,152 feet. A series of mountain ranges form a largely unbroken barrier up to 2,000 feet in altitude, with about half the length of the peninsula blocked up to 3,000 feet. The western slopes of the Sierra de Juárez and Sierra San Pedro Mártir, extending south about 160 miles from the border, are fairly gentle and descend to coastal plains along the Pacific. Most of the eastern slopes, however, are steep escarpments, plunging down to sweltering lowlands along the Río Colorado and the Cortez. A series of mountain ranges runs south to the vicinity of La Paz. The central part of the Cape region is occupied by two rugged mountain ranges, the Sierra de la Victoria and the Sierra de la Laguna.

by:Walt Peterson ©

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