Mount Diablo State Park

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View of Mt. Diablo from  above the city of
View of Mt. Diablo from Dinosaur Hill Park above the city of Pleasant Hill

Mount Diablo State Park is a state park in California, USA.



The park surrounds and includes Mount Diablo, an isolated 1173 meter (3849 feet) peak that is visible from many places in the surrounding region. During the summer, visiblity can be somewhat hazy. The best views can be found the day after a winter storm. It is located south of the town of Clayton, California and north-east of Danville, California. It is accessible by motor vehicle, hiking, running, or bicycle (the record time from the Athenian School in the town of Diablo to the summit is under 45 minutes; casual riders should bring plenty of food and water). It is approximately 80 km² (20000 acres) in area, and its elevation varies from approximately 90 meters (300 feet) to the summit height. Little more than a mile northeast of the summit is North Peak at 3557 feet.

Missing image
Mt. Diablo's North Peak

According to a sign at the summit it is possible to view the second greatest surface area seen from any peak in the world, exceeded only by the 19,340 foot Mount Kilimanjaro in Africa. However, this is probably a myth. While the lack of surrounding peaks gives Diablo an outstanding view, its relatively low height and the curvature of the earth limits the visible horizon to approximately 125 kilometers; several peaks around the world offer a greater viewing distance. However, it is plausible that more viewable area can be seen from the Diablo summit than any other peak in the lower 48 states.

Cultural history

Mount Diablo is sacred to many California Native American peoples; according to Miwok mythology, it was the point of creation. It derives its name from the escape of several Native Americans from the Spanish in a nearby willow thicket. The Spanish thus gave the thicket the name "Monte del Diablo", meaning "thicket of the devil", which was misunderstood by English-speaking newcomers to refer to the mountain. In 1851 the mountain was selected by Colonel Leander Ransom as the reference point for the surveying of the region, and much of California, Nevada and Oregon was surveyed from this base. Toll roads up the mountain were created in 1874 by local hoteliers, and an aerial navigation beacon was erected at the summit in 1928. After an initial purchase in 1921, the state of California acquired enough land in 1928 to create a small state park around the peak. Many improvements were carried out in the 1930s by the Civilian Conservation Corps. This initial park has been greatly expanded over the years, often barely ahead of real estate developers, to create the present state park. Now, the park in many places on its western side adjoins parklands of the East Bay Regional Park District, in turn adjoining protected areas owned or controlled by local cities such as the Borges Ranch Historic Farm and nearby Shell ridge and Indian Valley, owned by the city of Walnut Creek. State park expansion continues on the northern and eastern sides of the mountain. In 2005, a man from the neighboring town of Oakley petitioned the federal government to change the name of the mountain, claiming it offended his Christian beliefs and that, "when you start mentioning words that come from the dark side, evil thrives."

Natural history


View SW across the park from near the summit of Mt. Diablo
View SW across the park from near the summit of Mt. Diablo

The mountain is the result of geologic compression and uplift caused by the movements of the earth's plates. The mountain lies between converging earthquake faults and continues to grow slowly. The uplift and subsequent weathering and erosion has exposed ancient ocean bottom that now forms the summit. This hard red Franciscan shale is sedimentary in origin and therefore rich in microscopic fossils. In the western foothills of the mountain there are large deposits of younger sandstone and limestone rich in seashells, severely tilted and in places forming dramatic ridgelines. There are deposits of glassmaking grade sand and lower quality coal to the north of the mountain, which were formerly mined in the 1800s and early 1900s, but are now open to visitors as the Black Diamond Mines regional preserve. Guided tours of sand and coal mines are provided here.


The park's vegetation is mixed oak and open grassland country with extensive areas of chaparral and a number of endemic plant species, including substantial thickets and isolated examples of poison oak. It is best to learn to the characteristics of this shrub and its toxin before hiking on narrow trails through brush and to be aware that it can be bare of leaves (but toxic to contact) in the Winter. At higher altitudes there are stands of Knobcone pine, Foothill pine, and Coulter pine (for which the park marks the northern extreme of the range).


All vegetation, minerals and wildlife within the park are protected and it is illegal to remove such items or to harass any wildlife.

Commonly seen animals include Black-tailed Deer, California Ground Squirrels, Fox Squirrels and Gray Foxes; many other mammals including Mountain lions are present. It is the chief remaining refuge for the endangered Alameda Whipsnake. There are also exotic (non-native) animals such as the Red Fox and Opossum, the latter being North America's only Marsupial.

In the September and October you may encounter the male Tarantula spider (fearsome in appearance but harmless if undisturbed) as he seeks a mate. More dangerous are the black widow and brown recluse spiders, far less likely to be encountered in the open.

Of special note as a potential hazard is the Northern Pacific Rattlesnake. While generally shy and non-threatening, one should be observant and cautious of where one steps to avoid accidentally disturbing one.

There has also been an increase in the Mountain lion population in the larger region and one should know how to respond to these animals if encountered. Please see the mountain lion safety tips in the Mountain lion article.

One should avoid ground and brush contact to avoid fleas and ticks and the various diseases that they may transmit, including, respectively, bubonic plague and lyme disease.

Mosquitos have always been somewhat hazardous in this area as they have been known to carry western equine encephalitis, caused by a virus dangerous to humans. With the recent spread into the counties around Mount Diablo of the recently introduced West Nile virus, mosquitos are now far more hazardous, as this debilitating and frequently fatal disease is carried by (and can be fatal to) bird populations. Mosquitos are particularly active for about two hours after sunset and can be present in large numbers near creeks and during spring and fall wet seasons and after the rare summer rainfalls. Insect repellant containing the chemical DEET is recommended.


Missing image
Summit building, Mt. Diablo

Gatehouses are located at the end of Northgate Road (in Walnut Creek and Diablo Road (in Danville). The Danville entrance is also known as Southgate. If the gatehouses are not operating, proceed up the mountain to the ranger's station where the two entrance roads join, where the park fees may be paid.

From here the road reaches the summit of the mountain, where there is an observation building with a visitor's centre with natural history exhibits (presently closed due to California's budget constraints, but the roof viewpont remains accessible). On busy days it is advisable to park at the large parking lot near the summit and take a short walk up to the summit. At this lot you may encounter hang gliders ready for launch. There is also a restroom here and at the summit. From the elevation of the lower lot there is also a level wheelchair accessible trail with interpretive stations that extends part way around the mountain. There are numerous hiking trails and some paths available for mountain biking and horse riding. Camping facilities are available within the park. There are numerous picnic sites. Pets are restricted and require proper documentation for rabies (not just a tag). Daytime visitors must exit the park by sunset except for special events. Some picnic spots may be reserved but most are available without reservation.

Alcohol is strictly forbidden in the park. Fires are allowed only during the wet season (generally December through April), and only in sanctioned fire pits. The park may be closed on windy days during the dry season due to extremely hazardous fire conditions.

Two additional entrances with parking for hikers are provided on the northwest side of the park at Mitchell Canyon and Donner Canyon. Mitchell Canyon provides easy access to Black Point and Eagle Peak. Donner Canyon provides hikers access to Eagle Peak, Mount Olympia, North Peak, and the popular Falls Trail, which features several seasonal waterfalls.


On December 7th of each year the aircraft beacon atop the summit building is iluminated from sunset to dawn. A ceremony memorializing the attack on Pearl Harbor on this day in 1941 is held at the summit, with some of the few remaining survivors present. The public is welcome and visitors on this day should enter the park before 4:30 PM. Visitors may leave later than usual - this is one of the few opportunities to view the sunset from the peak, weather permitting, without an overnight stay. More interesting than the sunset itself is the view of the progression of the mountain's shadow across the great central valley to the distant Sierra Nevada, finally appearing for a few moments above the horizon as a shadow in the post-sunset sky glow.

Occasionally there will be public access to astronomical observations made by a local astronomy club. This club has been allocated a small parcel on the mountain and is developing a permanent observatory at this location. The instrument to be installed will have digital imaging capabilities and visitors will be able to take home an astronomical image that they may display on their home computer system.

External links


  • Information from the California State Parks leaflet on Mount Diablo State Park, issue 8/01, 2000.

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