Southern California’s Highest Mountain

Google Earth Pro Oct., 2019 image showing location of San Gorgonio Mountain.

 San Gorgonio Mountain is the highest peak [11,503 feet (3506 m)] in southern California. The peak is 27 mi (43 km) east of the city of San Bernardino, San Bernardino County and is a easy drive from most of Los Angeles and Orange counties. It is the peak with the greatest vertical gain (5,840 feet) in California. The mountain hosts the longest recorded line of sight in the contiguous United States; it is plainly visible from the summit of Mt. Whitney, 190 miles away.

View north-northeast from a commercial airliner. Image taken in mid July, 2010.

Closer view north from the same airliner. San Gorgonio Mountain has a few patches of snow near its summit. Under the wing, Big Bear Lake is visible. The mountain has a somewhat pyramid shape with a steep north face and a slightly shallower south face. 

An even closer view of summit of San Gorgonio Mountain. The summit plateau is large and broad (1 square mile). The summit has an Alpine climate, and snow can be present, even as late as mid-July. 

Northwest view of San Gorgonio Mountain (its summit has a few patches of snow left on it). Three major southern California rivers have their source on the mountain: the Whitewater River (shown here just right of the center of image), the San Gorgonio River, and the Santa Ana River.

San Gorgonio Mountain is part of the Transverse Ranges, an east-to-west mountain chain formed by tectonic forces between the Pacific and North American plates along the San Andreas fault, which lies just south of San Gorgonio Mountain.

The mountain is a massive block of quartz monzonite igneous rock (please see my earlier post--March 3, 2017, San Andreas Fault Displacement of a Distintive Granite), which sits on an ancient platform of Precambrian gneissic metamorphic rocks. Glacial and fluvial deposits dominate the surface of the lowest part of the mountain. During the Pleistocene “Ice Age,” there were two separate episodes of glaciation (both Wisconsin age, which was 75,000 to 11,000 years ago) on San Gorgonio Mountain, as evidenced by cirques and huge terminal embankments of coarse angular debris, up to 700 feet thick.