Facts

Mount Diablo is a 3849’ mountain in Contra Costa County, California located approximately 30 miles east of San Francisco. Subsidiary peaks are: North Peak (3,557’), Mt Olympia (2946’), Eagle Peak (2369’), and Mt. Zion (1635’).

The preserved lands of Mount Diablo total more than 90,000 acres and include 520 miles of trail and 400 miles of fire roads. Mount Diablo State Park itself is approximately 20,000 acres.

Mount Diablo provides habitat for over 100 species of animals and 650 species of flowering plants. There are 12 species of endangered plants and animals.

About 40,000 square miles of California and Nevada are visible from the summit. The visible non-mountainous horizon is approximately 78 miles. On a clear day, from the summit, it is possible to view parts of 35 of California's 58 counties and landmarks that include:

East: The Sierra Nevadas and Half Dome in Yosemite National Park, 125 miles away, can be viewed with a telescope.

West: Golden Gate Bridge and Farallon Islands.

Southeast: James Lick Observatory on Mount Hamilton (4,213’)

South: Mount Loma Prieta (3,791’) in the Santa Cruz Mountains

North: Mount Saint Helena (4,344’) and Mount Lassen (10,466’) 180 miles away, San Joaquin and Sacramento Rivers form the Delta

The Spanish name Diablo (meaning devil) is believed to have originated stem from an 1805 Spanish military expedition that went in search of runaway Native Californians from San Francisco's Mission Delores. The Spanish soldiers caught sight of the runaways hiding in a willow thicket near what is now Buchanan Field in Concord and decided to wait until the next morning before capturing them. During the night, the group of Native Californians mysteriously escaped. In response, the Spanish dubbed the site Monte del Diablo, meaning “Thicket of the Devil”. Subsequently, English speaking individuals believed monte translated to mountain and thus, tagged the summit of the nearly mountain Mount Diablo.

Mount Diablo has had many Indian names. They include: Tuyshtak (Ohlone/Costanoan) meaning “at the day”, 'Oj-ompil-e (Northern Miwok), Supemenenu (Southern Miwok), Sukku Jaman, meaning “the place where dogs came from in trade” (Nisenan) and Kawukum. An early Spanish name for the peak was Cerro Alto de los Bolbones, meaning “High Point of the Volvon Indians”.

Mount Diablo was sacred to many California Native American peoples. The major tribes of the region were: Ohlone, Miwok, and Yokut. Most of Mount Diablo was the homeland of the Volvon, a Bay Miwok group. The native peoples relied on food gathering of acorns, buckeye, laurel, pine seeds, plant seeds, and Brodiaea bulbs.

Animal life includes: coyote, bobcat, black-tailed deer, squirrel, grey fox, mountain lion, Alameda whipsnake, California red-legged frog, peregrine falcon, ringtail cat, American badger, San Joaquin kit fox, roadrunner, California tiger salamander, burrowing owl, red fox, opossum, tarantula, black widow spider, bald eagle, golden eagle, raccoon, many bird and insect species, and rattlesnake.

The warmest month on the mountain is July with an average high of 85°F and an average low of 59°F. The coolest month is January with an average high of 55°F and an average low of 39°F. The highest temperature recorded has been 111°F and the lowest temperature recorded was 14°F.

Annual precipitation averages 24”. The most rain recorded in a month was 13.5”. The most rain recorded in a day was 5”. The average annual days with measurable precipitation is 65 days.

Snowfall averages 1” each year. The most snowfall observed in a month was 17”. The greatest snow depth was 3”. Measurable snowfall does not occur every year, so the annual average days with measurable snowfall is only .5 days.

The mountain lies between earthquake faults and is the result of compression and uplift caused by the movements of the earth's plates. The mountain continues to grow from 3-5 mm each year. The tilted layers stand almost vertically in places such as Rock City, Castle Rock, Fossil Ridge, and Devil's Slide. Erosion has carved wind caves and tunnels in the rocks.

The summit of Mount Diablo is made up of graywacke (gray sandstone), red chert (formed from ocean animal skeletons settling to the ocean floor forming a silica ooze that ultimately solidified), greenstone (oceanic volcanic basalts), and shale. The oldest rocks on the mountain are the greenstones formed about 190 million years old.

Sand and coal on the north of the mountain were formerly mined in the Black Diamond Mines Regional Preserve during the 1800s and early 1900s. On the west side there are large deposits of sandstone rocks rich in seashells because millions of years ago much of California was an inland sea.

This trail stretches from Mount Diablo’s South Gate to the summit. The trail is 6.25 miles in length with a vertical elevation gain of 2,940’. It is a journey through geologic time of 190 million years, walking from younger rocks to older rocks.

This trail lies just below the summit and encircles the summit. The trail is an easy 0.7-mile loop. Originally the trail was named after the 6,000-acre fire that occurred in 1977. The trail is now named for Mary Bowerman, a Mount Diablo botanist for 75 years and co-founder of Save Mount Diablo.

Mount Diablo State Park - www.parks.ca.gov/?page_id=517

    
       Maternal rock giving birth at Rock City.

The ceremonial bay laurel grove at our campsite

  

 


View of the summit from Mary Bowerman Trail


Sunrise: view from the Mary Bowerman Trail on our last day