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Coastal Cosmos

San Diego isn’t flat

We are coastal inhabitants. We live between three and about 400 feet above sea level. But San Diego County is not a flat, static landscape. Just off the coast, the dynamic geography rises into peaks, drops into canyons, then up over taller mountains before diving into the Colorado Desert and Anza-Borrego Desert State Park. The mountains of San Diego County tell the geologic history of our beautiful home and provide countless opportunities for recreation and adventure.From all over the coast, peaks can be observed rising into the sky just inland. These closest peaks are just the beginning of a system of mountains called the Peninsular Ranges. These ranges extend from Southern California all the way to the southern tip Baja Peninsula. The Peninsular Ranges are part of a much larger group of mountain ranges called the Coast Ranges or Pacific Mountain System. These ranges extend along the Pacific coast of North America from Alaska through Canada all the way to Mexico.

These ranges, in turn, are part of an even larger system of mountain ranges named the North American Cordillera, consisting of all the mountains of western Canada, the United States and Mexico. Finally, the largest group of mountains in the Western Hemisphere is the American Cordillera. Including all the major mountains of western North America, through the Andes of South America and even into Antarctica. This is essentially the eastern rim of the Ring of Fire and the backbone for half of planet Earth.

San Diego’s Peninsular Range Mountains are formed from the same enormous block of intrusive (formed inside the Earth), granitic rock as the majestic Sierra Nevada Mountains. Beginning 120 million years ago, an ocean of liquid rock or magma began to freeze and harden under the Earth’s surface. A finger of this batholith, called a pluton (after Pluto, god of the underworld) sits underneath San Diego County and is exposed as the peaks and ridgelines that we see from the coast.

Our county is striped with fault lines that grind and uplift the pluton. Millions of years of plate tectonics and weathering continue to form the distinctive contours of these plutonic rocks.

One of the closest mountains to the coast and visible from any coastal highpoint or lagoon is 1,554 foot Black Mountain. Located nine miles from the ocean near Rancho Peñasquitos, Black Mountain is characterized by the large antenna on its summit. Directly east of Black Mountain and often visible from the coast sits Mt. Woodson. Rising 2,881 feet above sea level, Mt. Woodson is recognized by the spheroidal weathering of its boulders. Directly south lies 2,696 foot Iron Mountain, a very popular hiking location.

Beyond these peaks, San Diego County rises into larger mountain ranges including the Palomar Mountains, home of the world-famous 200-inch Hale Telescope. The observatory dome is surprisingly visible from a distance. The Cuyamaca Mountains contain the prominent 6,512-foot Cuyamaca Peak. Much of this mountain wilderness is part of the Cleveland National Forest. The high point of San Diego County is near Warner Springs on the Los Coyotes Indian Reservation. Hot Springs Mountain rises to an elevation of 6,533 feet.

The colossal geologic forces that uplift mountains and the persistent meteorological forces that shape them are evident throughout San Diego County. The hiking, biking and trail-running adventures are extensive. The opportunities to enjoy the geology and the resulting ecology are widespread. Although we are coastal inhabitants, we are fortunate to have such dynamic geography in our backyard.

Kyle Stock is originally from Ohio, is a passionate surfer, backpacker, astronomer, gardener, backyard scientist, runner, reader and K-6 science teacher at Solana Santa Fe Elementary in the Solana Beach School District. He can be contacted at

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