Editing Mount Diablo

{{short description|Mountain in California, US}}
{{other uses}}
{{Use mdy dates|date=May 2017}}

{{More citations needed|date=March 2025}}{{Infobox mountain
| name = Mount Diablo
| native_name = {{plain list|
* {{native name|cst|tuyshtak|tuištak}}
* {{native name|nsq|oj·ompil·e}}
* {{native name|csm|supemenenu}}
* {{native name|nsz|sukkú jaman}}
}}
| other_name = {{lang|es|Cerro Alto de los Bolbones}}
| photo = View of Mount Diablo and CA highway 24 from Lafayette Hights.jpg
| photo_caption = West face of Mount Diablo and [[California State Route 24|Hwy 24]]
| elevation_ft = 3849
| elevation_ref = {{NAVD88}}<ref name="ngs">
  {{cite ngs
  | id = HS5120
  | designation = Mount Diablo
  | access-date = June 28, 2009 }}</ref>
| prominence_ft = 3109
| prominence_ref = <ref name="pb"/>
| range = [[Diablo Range]]
| parent_peak =
| listing = [[List of California county high points|California county high points]] 45th
| location = [[Contra Costa County, California]], U.S.
| map = USA California#USA
| map_caption = none
| map_size = 220
| coordinates   = {{coord|37.881697781|N|121.914154997|W|type:mountain_region:US-CA_scale:100000_source:ngs|format=dms|display=inline,title}}
| coordinates_ref = <ref name="ngs"/>
| topo = [[United States Geological Survey|USGS]] Clayton
| type = [[Sedimentary rock|Sedimentary]]
| age = [[Cretaceous]], [[Jurassic]]
| easiest_route = Paved road
| embedded = {{designation list | embed = yes
  | designation1 = NNL
  | designation1_date = 1982
  }}
{{Designation list|embed=yes|designation1=California|designation1_number=905<ref name=CHL>{{cite ohp|905|Mount Diablo|2012-10-06}}</ref>}}
}}

'''Mount Diablo''' is a mountain of the [[Diablo Range]], in [[Contra Costa County, California|Contra Costa County]] of the eastern [[San Francisco Bay Area]] in [[Northern California]]. It is south of [[Clayton, California|Clayton]] and northeast of [[Danville, California|Danville]]. It is an isolated upthrust peak of {{convert|3849|ft|m|0|abbr=off|sp=us}}, visible from most of the San Francisco Bay Area. Mount Diablo appears from many angles to be a double pyramid and has many subsidiary peaks. The largest and closest is North Peak, the other half of the double pyramid, which is nearly as high in elevation at {{convert|3557|ft|m|0}}, and is about {{convert|1|mile|spell=in|abbr=off|sp=us}} northeast of the main summit.

The mountain is within the boundaries of '''Mount Diablo State Park''', which is administered by [[California State Parks]].

==Geography==

The summit is accessible by foot, bicycle, or motor vehicle.  Road access is via North Gate Road or South Gate Road.

=== Mount Diablo State Park ===

The peak is in Mount Diablo State Park, a [[state park]] of about {{convert|20000|acres|sigfig=1|abbr=off|sp=us}}.<ref>{{Cite news|url=https://www.mercurynews.com/2019/05/12/state-parks-standstill-why-california-hasnt-opened-a-new-state-park-in-10-years/|title=State parks standstill: Why California hasn't opened a new state park in 10 years|last=Rogers|first=Paul|date=2019-05-12|website=The Mercury News|language=en-US|access-date=2019-05-12|df=mdy-all}}</ref>{{Failed verification|date=March 2025}} The state park was the first public [[Open space reserve|open space]] established on or near the peak. According to the non-profit Save Mount Diablo, there are now varied types of protected lands on and around Mount Diablo that total more than {{convert|90000|acres|sigfig=2}}. These include 38 preserves, such as nearby city open spaces, regional parks, and [[drainage basin|watershed]]s, which are buffered in some areas with private lands that have been protected by conservation [[easement]]s.

===Viewshed===

On a clear day, the [[Sierra Nevada (U.S.)|Sierra Nevada]] range is plainly visible from the summit. The best views are after a winter storm; a snowy Sierra shows up better, and summer days are likely to be hazy. [[Lassen Peak]], {{convert|181|mi|km|abbr=off|sp=us}} away, is occasionally just visible over the curve of the earth.<ref name="HeyWhatsThatViewShed">{{cite web|title=Mt Diablo Viewshed|url=http://www.heywhatsthat.com/?view=BPMSFOEL|website=HeyWhatsThat.com|access-date=July 4, 2014}}</ref><ref name="PeakFinderMtDiabloView">{{cite web|title=Computer Generated View from Mt Diablo|url=http://www.peakfinder.org/?lat=37.8821&lng=-121.915&ele=1160&name=Mount%20Diablo&zoom=7&dir=9|website=www.peakfinder.org}}</ref> [[Sentinel Dome]] in [[Yosemite National Park]] is visible,<ref name="SentinelDomeViewAtPeakfinder">{{cite web|title=Synthetic View from Sentinel Dome to Mt Diablo|url=http://www.peakfinder.org/?lat=37.7238&lng=-119.585&ele=2475&name=Sentinel%20Dome&zoom=7&dir=275|website=www.peakfinder.org|access-date=July 5, 2014}}</ref> but [[Half Dome]] is hidden by the 8000-foot ridge at 37.755N 119.6657W. Eight bridges are visible, from left to right (southwest to northeast): [[San Mateo Bridge|San Mateo]], [[San Francisco Bay Bridge|Bay]], [[Golden Gate Bridge|Golden Gate]], [[San Rafael Bridge|San Rafael]], [[Carquinez Bridge|Carquinez]], [[Benicia Bridge|Benicia]], [[Antioch Bridge|Antioch]], and [[Rio Vista Bridge|Rio Vista]].

Many peaks in the state are taller, but Mount Diablo has a remarkable [[topographical prominence|visual prominence]] for a mountain of such low elevation. Its looming presence over much of the [[San Francisco Bay Area|Bay Area]], [[Sacramento-San Joaquin River Delta|delta]], and [[Central Valley (California)|Central Valley]], and good visibility even from the [[Mother lode#California Mother Lode|Mother Lode]], all key regions during the [[California Gold Rush|gold rush]] and early [[List of U.S. states by date of statehood|statehood]], made it an important landmark for mapping and navigation.  The summit is used as the reference datum for land surveying in much of northern California and Nevada.

It boasts one of the largest viewsheds in the Western United States and played a key role in California history.<ref>{{cite web |last1=Ehsanipour |first1=Asal |title=Does Mount Diablo Have the Biggest View in the World? |url=https://www.kqed.org/news/11808501/does-mount-diablo-have-the-biggest-view-in-the-world |website=Bay Curious |date=March 26, 2020 |publisher=KQED |access-date=16 August 2020}}</ref>

[[File:Mount Diablo Panoramic From Newhall.jpg|thumb|center|800px|View of Mount Diablo from [[Concord, California|Concord]]: north peak (left), Mount Zion (center), and main peak (right), ]]

==Cultural history==
[[File:Mount Diablo Summit.JPG|right|thumb|The summit of Mount Diablo]]
Mount Diablo is sacred to many California [[Native Americans in the United States|Native American]] peoples. According to [[Miwok mythology]] and [[Ohlone mythology]], it was the point of creation. The local peoples of the area traditionally had a variety of creation narratives associated with the mountain. In one surviving narrative fragment, Mount Diablo and Reed's Peak ([[Mount Tamalpais]]) were surrounded by water; from these two islands the creator Coyote and his assistant Eagle-man made Native American people and the world.<ref name="MDIA" /> In another, Molok the Condor brought forth his grandson Wek-Wek the Falcon Hero, from within the mountain.<ref>{{cite book |last=Merriam |first=C. Hart |year=1910 |title=The Dawn of the World: Myths and Weird Tales Told by the Mewan Indians of California |url=https://archive.org/details/dawnworldmythsa00merrgoog |location=Cleveland |publisher=Arthur H. Clark |oclc=2581152}}</ref>

===Earliest names===

[[File:Mt diablo north peak.jpg|thumb|View of Mount Diablo's North Peak from the main peak]][[File:Mount Diablo California from Concord.jpg|thumb|Aerial view of the Los Medanos foothills and Mount Diablo from over Suisun Bay at [[Concord, California]]]]About 25 independent tribal groups with well-defined territories lived in the East Bay countryside surrounding the mountain at time of European contact.  Their members spoke dialects of three distinct languages: [[Ohlone language|Ohlone]], [[Bay Miwok language|Bay Miwok]], and [[Northern Valley Yokuts]].<ref>Milliken, Randall, (2008) ''Native Americans at Mission San Jose'', 2008, Malki-Ballena Press.</ref> The [[Chochenyo language|Chochenyo]]-speaking Ohlone from [[Mission San José (California)|Mission San Jose]] and the East Bay area, call the mountain {{lang|cst|Tuyshtak}}, meaning "at the dawn of time". Further inland, the [[Nisenan]] of the Sacramento Valley call it {{lang|nsz|Sukkú Jaman}}, "dog mountain"; because, as Nisenan elder Dalbert Castro once explained, it's "the place where dogs came from in trade".<ref>{{cite web |url=http://www.savemountdiablo.org/AboutMountDiablo.htm |title=About Mount Diablo |publisher=SaveMountDiablo.org |access-date=November 15, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20100212222122/http://www.savemountdiablo.org/AboutMountDiablo.htm |archive-date=February 12, 2010 |df=mdy-all }}http://www.savemountdiablo.org/why_mtdiablohistory.html {{Webarchive|url=https://web.archive.org/web/20160304223657/http://www.savemountdiablo.org/why_mtdiablohistory.html |date=March 4, 2016 }}</ref><ref name="ortiz" /> A Southern Sierra Miwok name for the mountain is {{lang|csm|Supemenenu}}, and a Northern Sierra Miwok name is {{lang|nsq|Oj·ompil·e}}.<ref name="ortiz" />

It has also been suggested that another early Native American name for the mountain was {{lang|und|Kawukum}} or {{lang|und|Kahwookum}}, but there is no evidence to confirm the assertion. According to Indian historian Bev Ortiz and Save Mount Diablo:<ref>{{cite web |url=http://www.savemountdiablo.org/News_Press_Release/mount_kawukum.htm |title=Mount Kawukum? Save Mt. Diablo's Name |publisher=SaveMountDiablo.org |archive-url=https://web.archive.org/web/20070624211340/http://www.savemountdiablo.org/News_Press_Release/mount_kawukum.htm |archive-date=June 24, 2007 |access-date=November 15, 2015}}</ref> "The name {{lang|und|Kahwookum}} was made up in 1866 — with no real Native American connection — referred to the California Legislature's Committee on Public Morals, and tabled. It resurfaced as a real estate gimmick in 1916 with a supposed new translation, "Laughing Mountain", attributed without documentation to Diablo area Volvon Indians.<ref name="ortiz">{{cite journal |last=Ortiz |first=Bev |title=Mount Diablo as Myth and Reality: An Indian History Convoluted |journal=American Indian Quarterly |date=Autumn 1989 |volume=13 |issue=4 |pages=457–470 |doi=10.2307/1184528 |jstor=1184528 |url=https://www.jstor.org/stable/1184528 |url-access=subscription }} explains the mountain's naming and debunks the name "Kahwookum" as fictitious.</ref>

Most of Mount Diablo, including its peak, was within the homeland of the early [[Bay Miwok|Volvon]] (sometimes spelled Wolwon, Bolbon or Bolgon), a [[Bay Miwok language|Bay Miwok]]–speaking tribe. As early as 1811, Spanish colonists referred to the mountain as {{lang|es|Cerro Alto de los Bolbones}} ("High Hill of the Volvon") or sometimes {{lang|es|Sierra de los Bolgones}}.<ref>{{cite web |url=http://johnmarshhouse.com/park/native-americans/ |title=John Marsh Historic Trust}}</ref>

===Current name===

The conventional view is that the peak derives its name from the reaction of Spanish soldiers to the 1805 escape of several [[Bay Miwok|Chupcan]] Native Americans in a willow thicket some {{convert|7| miles||spell =in}} north of the mountain. One story tells that their nighttime escape through the thicket was aided by mysterious lights.<ref name="hulaniski-3">{{cite book
  |last=Hulaniski
  |first=F.J.
  |date=1917
  |title=The History of Contra Costa County California
  |location=Berkeley
  |publisher=Elm Publishing
  |chapter=3 |url=http://genealogytrails.com/cal/costa/books/history_of_cc_chapter3.html
  }}</ref> An 1850 report by General [[Mariano G. Vallejo]] tells of a strange dancing spirit turning the battle in favor of the Chupcan. Vallejo interpreted the natives' word for the personage, {{lang|und|puy}}, to mean "devil" in the Anglo-American language.<ref name="hulaniski-14">{{cite book
  |last=Hulaniski
  |first=F.J.
  |date=1917
  |title=The History of Contra Costa County California
  |location=Berkeley
  |publisher=Elm Publishing
  |chapter=14
  |url=http://genealogytrails.com/cal/costa/books/history_of_cc_chapter3.html
  }}</ref><ref>{{cite book
  | last =Cunningham
  | first =Mark
  | title =The Green Age of Asher Witherow
  | url =https://archive.org/details/greenageofasherw00cunn
  | url-access =registration
  | publisher =Unbridled Books
  | year =2004
  | page =288
  | isbn =1-932961-13-5
  }}; for one interpretation of the context of the Spanish attack on the Chupcan, see Milliken, Randall, (1995) ''A Time of Little Choice: The Disintegration of Tribal Culture in the San Francisco Bay Area, 1769-1810'', Menlo Park, California: Ballena Press, pp.184-185, 241
</ref>  Vallejo's report could be interpreted to align with Edward G. Gudde's history of place names. (Kyle, and Ortiz)<ref name="MDIA"/><ref>{{cite book |last=Gudde |first=Edward G. |title=One Thousand California Place Names: The Story Behind the Naming of Mountains, Rivers, Lakes, Capes, Bays, Counties and Cities |edition=3rd |publisher=University of California Press |year=1969 |isbn=0-520-01432-4 |url=https://archive.org/details/1000californiapl00gudd }}</ref>

By 1824, the region north of the mountain came to be known as ''Monte del Diablo'' ("devil's thicket"; in this case ''monte'' should be translated as thicket or dense woods). It was shown on maps near present-day Concord (formerly known as [[Pacheco, California|Pacheco]]).<ref>''Plano topografico de la Misión de San José''</ref> Later, U.S. settlers understood "Monte" to refer directly to the mountain, and it was recorded with varying degrees of certainty until "Mount Diablo" became official in 1850.<ref name="ortiz"/>

In May 1862, California Geological Survey field director William H. Brewer named the northeast peak of Mount Diablo "Mount King", after Rev. [[Thomas Starr King]], a Unitarian clergyman, abolitionist, Republican, Yosemite advocate, cultural Unionist, and California's leading intellectual. Today it is known as North Peak.<ref>{{cite book |last1=Browning |first1=Peter |title=Yosemite Place Names |date=1988 |publisher=Great West Books |location=Lafayette, Calif. |isbn=0-944220-00-2 |page=[https://archive.org/details/yosemiteplacenam00brow/page/137 137] |url=https://archive.org/details/yosemiteplacenam00brow/page/137 }}</ref>

===Mount Diablo  ===

[[File:Mount Diablo in with San Francisco Bay and Richmond–San Rafael Bridge.JPG|thumb|Mount Diablo with the [[San Francisco Bay]] and [[Richmond–San Rafael Bridge]] in the foreground]]
In 2005 Arthur Mijares, from the neighboring town of [[Oakley, California|Oakley]], petitioned the federal government to change the name of the mountain,<ref>'' Contra Costa Times'', October 14, 2005, "Board Decides Mount Diablo Will Keep Name", accessed 06-10-17</ref> claiming it offended his Christian beliefs.  Additionally, he claimed that Diablo is a living person, and so is banned under federal law.<ref name="DiablotoReagan">{{cite news
 | title = Man Petitions to Change Name of Mount Diablo to Mount Ronald Reagan
 | first = Matthias
 | last = Gafni
 | url = http://www.contracostatimes.com/news/ci_14284156?nclick_check=1
 | newspaper = Contra Costa Times
 | date = January 27, 2010
 | access-date = January 28, 2010
 }}</ref> He suggested renaming the mountain Mount Kawukum, and later, Mount [[Yahweh]]. Suggestions by other individuals included Mount [[Miwok]] and Mount [[Ohlone]], after local Indian tribes.  Finally Mijares proposed Mount [[Ronald Reagan|Reagan]],<ref name="DiablotoReagan"/> but the board rejected it on the grounds that a person must be deceased for five years to have a geographic landmark named after them. Eventually, the [[U.S. Board on Geographic Names]] rejected the petitions, saying there was no compelling reason to change the name.

In 2009 Mijares again proposed the name Mount Reagan to the United States Board of Geographic Names because the late president was by then eligible.<ref name="DiablotoReagan"/> The board gave the Contra Costa County Supervisor's Committee until March 31 to file an opinion. Individual members of the committee have responded that although they respect Reagan, Mount Reagan is not an appropriate name for the historic mountain.<ref name="DiablotoReagan"/> Later, the board unanimously voted against renaming the mountain, citing its historical significance.<ref name="2010renamefails">{{cite news|url=http://www.aolnews.com/nation/article/devil-trumps-reagan-in-duel-over-mount-diablos-name/19371355|title=Devil Trumps Reagan in Duel Over Landmark|last=Paddock|first=Richard|date=February 24, 2010|publisher=[[AOL News]]|access-date=March 2, 2010|url-status=dead|archive-url=https://web.archive.org/web/20100227182245/http://www.aolnews.com/nation/article/devil-trumps-reagan-in-duel-over-mount-diablos-name/19371355|archive-date=February 27, 2010|df=mdy-all}}</ref>

===Early uses===

In 1851 the south peak of the mountain was selected by Colonel [[Leander Ransom]] as the [[datum (geodesy)|initial point]]—where the Mount Diablo Base and [[Mount Diablo Meridian]] lines intersect—for [[cadastral]] surveys of a large area.  Subsequent surveys in much of [[California]], [[Nevada]] and [[Oregon]] were located with reference to this point.

[[Toll road]]s up the mountain were created in 1874 by Joseph Seavey Hall and William Camron (sometimes "Cameron"); Hall's Mount Diablo Summit Road was officially opened on May 2, 1874.  Camron's "Green Valley" road opened later.  Hall also built the 16-room Mountain House Hotel near the junction of the two roads, a mile below the summit (2,500 foot elevation. (It operated through the 1880s, was abandoned in 1895, and burned c. 1901). As far north as Meridian Road, on the outskirts of [[Chico, California]], the summit was used as a reference point. The road is colinear with the summit, and is named for the meridian which intersects it.

An aerial [[navigation]] beacon, the Standard Diablo tower, was erected by [[Standard Oil]] at the summit in 1928.<ref name=save_md/> The 10-million-candlepower beacon<ref>A Standard ad (''Aviation Week'', October 30, 1961, p14) depicts a focused beam, unlike the present light.</ref> became known as the "Eye of Diablo" and was visible for a hundred miles.<ref name="MDIA"/>

===Protection of the area===
[[File:MountDiablo.JPG|thumb|left|Mount Diablo from the Berkeley–Oakland hills]]
After initial legislation in 1921, the state of California acquired enough land in 1931 to create a small state park around the peak. Many improvements were carried out in the 1930s by the [[Civilian Conservation Corps]], but park expansion slowed in the 1940s through the 1960s.

Significantly, botanist [[Mary Bowerman|Mary Leolin Bowerman]] (1908–2005), founder of the Save Mount Diablo non-profit in 1971, published her Ph.D. dissertation in 1936 at the [[University of California, Berkeley]]. In 1944 she published her book, ''The Flowering Plants and Ferns of Mount Diablo, California''. Her study boundaries became the basis for the state park's first map and for the park's eventual expansion. Her work also became the origin of many of the park's place names.<ref name="MDIA"/>

Mount Diablo was used for broadcasting purposes in the 1950s by radio station KSBR-FM and television station [[KOVR]] (channel 13). The Mount Diablo site gave KOVR, which was based in [[Stockton, California|Stockton]], regional coverage that also included San Francisco and [[Sacramento, California|Sacramento]]. However, it also forced the station to pay San Francisco rates for movies and impeded any attempt at obtaining network affiliation. In 1957, the station relocated to Butte Mountain in [[Jackson, California|Jackson]] in order to become an [[American Broadcasting Company|ABC]] affiliate and remove its signal from the Bay Area.

This state park has been greatly expanded over the decades. Soon after Earth Day in 1971, the nonprofit organization "Save Mount Diablo"<ref>{{cite web |url=http://www.savemountdiablo.org |title=Save Mount Diablo |publisher=SaveMountdiablo.org}}</ref> was created by co-founders Mary Bowerman and Art Bonwell, barely ahead of real estate developers. At the time, the state park included just {{convert|6788|acres}} and was the only park in the vicinity of the mountain. In 2007 the state park totaled almost {{convert|20,000|acres}}, and with 38 parks and preserves on and around the mountain, Diablo's public lands total more than {{convert|90000|acres}}. According to Save Mount Diablo, there are 50 individual preserves on and around Mount Diablo, some of which are conservation easements covering a single parcel, others are expected to eventually be absorbed into larger nearby parks. As of December 2007, the organization recognizes 38 specific Diablo parks and preserves.{{Citation needed|date=July 2010}}

The State Park adjoins park lands of the [[East Bay Regional Park District]], including [[Morgan Territory Regional Preserve]], [[Brushy Peak Regional Preserve]], [[Vasco Caves Regional Preserve]], and [[Round Valley Regional Preserve]]. It also adjoins protected areas owned or controlled by local cities such as the [[Old Borges Ranch|Borges Ranch Historic Farm]], the [[Concord Naval Weapons Station]] (now in the process of being converted to non military use), Indian Valley, [[Walnut Creek Open Space|Shell Ridge Open Space and Lime Ridge Open Spaces]] near the [[Walnut Creek, California|city of Walnut Creek]], and east to the [[Los Vaqueros Reservoir]] watershed. The new [[Marsh Creek State Park (California)|Marsh Creek State Park]]{{efn|formerly known as Cowell Ranch State Park.}} and [[Black Diamond Mines Regional Preserve]] are among the open spaces stretching to the north. In this way the open spaces controlled by cities, the East Bay Regional Park District, Mount Diablo State Park, and various regional preserves now adjoin and protect much of the elevated regions of the mountain. There are unprotected areas in Arroyo del Cerro, Curry Canyon, the Marsh creek region, and on the northern slopes of North Peak, and in a number of inholdings surrounded by preserve land.

[[File:Franks Tract in Sacramento–San Joaquin River Delta with Mount Diablo in background.JPG|right|thumb|Mount Diablo as seen from [[Franks Tract State Recreation Area|Franks Tract]] in the [[Sacramento–San Joaquin River Delta]]]]

Park expansion continues on all sides of the mountain although its western boundaries are largely complete. Extensive development continues in the southwestern foothills and Tassajara region, such as the upscale development of [[Blackhawk, California|Blackhawk]] and individual estates overlooking the Livermore Valley on Morgan Territory Road. Other large projects are proposed in the northern Black Diamond Mines and Los Medanos foothills, at the Concord Naval Weapons Station, and near Marsh Creek State Park. Large-scale development of other private parcels is restricted by city and county urban limit lines, by lack of water, excessive slope, and sensitive resources including rare species.  Development of smaller ranchette subdivisions continue to fragment and threaten many parcels and large areas of habitat.{{cn|date=March 2025}}

===Map of protected lands===
In 2007 Save Mount Diablo published ''Mount Diablo, Los Vaqueros & Surrounding Parks, Featuring the Diablo Trail'', the most accurate and up-to-date map of Mount Diablo's more than {{convert|90000|acres}} of protected lands. It includes 100 access points, {{convert|520|mi}} of trail, and {{convert|400|mi}} of private fire roads.<ref>{{cite web |url=http://www.savemountdiablo.org/DiabloTrailMAPHomepage.htm |title=Mount Diablo, Los Vaqueros & Surrounding Parks, Featuring the Diablo Trail |publisher=SaveMountDiablo.org |access-date=November 15, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20100602214220/http://www.savemountdiablo.org/DiabloTrailMAPHomepage.htm |archive-date=June 2, 2010 |df=mdy-all }}http://www.savemountdiablo.org/lands_map.html</ref>

==Natural history==

===Geology===
[[File:Fossilized seashells at the summit of Mt. Diablo, CA.jpg|thumb|Fossilized sea shells in the sandstone at the summit of Mt. Diablo (about 3,800' [[mean sea level|MSL]])]]There are three major groups of rocks composing Mount Diablo -- the Mount Diablo Ophiolite group, dating to the Jurassic; the Franciscan Complex, dating to the Jurassic and Cretaceous; and the combination of the Great Valley Group (Jurassic and Cretaceous) and Younger Sedimentary rocks (Cenozoic).<ref name=":0">{{Cite web |title=Guide to Mount Diablo Geology |url=https://www.mdia.org/guide-to-mount-diablo-geology |access-date=2025-03-15 |website=Mount Diablo Interpretative Association |language=en}}</ref>

Ophiolite is a kind of rock that forms in [[Mid-ocean ridge|mid-ocean ridges]].<ref name=":0" /> The Coast Range Ophiolite is ancient oceanic crust caught between an ancient [[Subduction|subduction zone]] off California near the end of the Jurassic, and a former shoreline in the ancient Sierra foothills.<ref name=":0" /> This is the source of the ophiolite of Mount Diablo, called the Mount Diablo Ophiolite, which underlies it north of a line drawn from Long Ridge through Murchio Gap.<ref name=":0" /> Basalt, diabase, and serpentinite can be found.<ref name=":0" /> 

The Franciscan Complex underlies the central area of Mount Diablo's summit and the North Peak.<ref name=":0" /> It is an "accretionary complex", formed in an east-dipping subduction zone off California as part of the upper oceanic crust (pillow basalt) and what it carried (chert, graywacke, shale, small islands, sea mounts) were scraped off during the process of subduction.<ref name=":0" /> These elements were then mixed and partially subducted before ending up on and under the adjacent continental crust.<ref name=":0" /> [[Accretionary fault|Accretionary faulting]] forced the complex under the Coast Range Ophiolite (including the Mount Diablo Ophiolite), and their contact is a [[fault plane]], known as the Coast Range Fault.<ref name=":0" /> The Franciscan Complex likely underwent metamorphism there, around 12 miles deep.<ref name=":0" /> Today, on land, the Franciscan Complex is made up of numerous large and small blocks of various types of rock in a sheared matrix.<ref name=":1">{{Cite web |title=Mount Diablo State Park |url=https://www.parks.ca.gov/pages/734/files/GeoGem%20Note%208%20Mt%20Diablo%20State%20Park.pdf |website=Geological Gems of California |publisher=California State Parks}}</ref> Between the late Cretaceous and early Eocene, [[Extensional fault|extensional faulting]], and [[ductile thinning]] of serpentinite in the ophiolite, reduced the weight on the complex, causing it to rise to a depth of ~2 miles.<ref name=":0" />

The Great Valley Group is composed of sedimentary rocks deposited underwater between the Upper Jurassic and the Cretaceous between the ancient Sierra Nevada and the western subduction zone, over the ophiolite basement of the Central Valley.<ref name=":0" /> The Mount Diablo area, a persistent "high" though not yet a mountain, was intermittently submerged well into the Pliocene.<ref name=":0" /> This region surrounding Mount Diablo was uplifted during the [[Tertiary Period]].<ref name=":1" />

The Younger Sedimentary rocks are described in the following source but are not summarized here.<ref name=":0" />

Although the rocks are quite old, Mount Diablo itself is relatively young.<ref name=":0" /> The formation of the mountain began about 2 million years ago during the Pliocene.<ref name=":1" /> Between the Pliocene and the present, the Franciscan Complex and overlying Great Valley rocks were folded upward by compression caused by a blind [[thrust fault]] under the mountain.<ref name=":0" /> The fold is asymmetrical, and is moving southwest due to the blind thrust fault.<ref name=":0" /> After the fold was created, erosion removed overlying Great Valley rocks and exposed the Franciscan Complex in the center of the fold, resulting in the modern Mount Diablo.<ref name=":0" /> The mountain is still growing today, as it is squeezed between the active [[Greenville Fault]] and [[Concord Fault]], through large periodic earthquakes along the [[Mount Diablo Thrust Fault]].<ref name=":1" /> Historically this fault has not been seen to move, but a 1% chance is predicted that it will produce a large earthquake within 30 years.<ref name=":1" />

Mount Diablo's "wind caves" were created by water seeping through fractures in and dissolving the Domegine Sandstone.<ref name=":1" />

Deposits of glassmaking-grade sand and lower-quality [[coal]] north of the mountain were mined in the 19th and early 20th centuries, but are now open to visitors as the [[Black Diamond Mines Regional Preserve]]. Guided tours of the sand mines and coal field are provided.{{Citation needed|date=March 2025}}

===Vegetation===
{{Refimprove|section|small=y|date=March 2025}}
The park's vegetation is mixed [[oak]] woodland and savannah and open grassland with extensive areas of [[chaparral]] and a number of [[Endemism|endemic]] plant species, such as the [[Arctostaphylos auriculata|Mount Diablo manzanita]] (''Arctostaphylos auriculata''), [[Calochortus pulchellus|Mount Diablo fairy-lantern]] (''Calochortus pulchellus''), [[Campanula exigua|chaparral bellflower]] (''Campanula exigua''), [[Cordylanthus nidularius|Mount Diablo bird's beak]] (''Cordylanthus nidularius''), [[Phacelia phacelioides|Mount Diablo phacelia]] (''Phacelia phacelioides)'' and [[Helianthella castanea|Mount Diablo sunflower]] (''Helianthella castanea''). The park includes substantial thickets, isolated examples, and mixed ground cover of [[Toxicodendron diversilobum|western poison oak]]. (It is best to learn 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 and on north slopes is the widely distributed [[Pinus sabiniana|foothill pine]] (''Pinus sabiniana''). [[Pinus attenuata|Knobcone pine]] (''Pinus attenuata'') may be found along Knobcone Pine Road in the southern part of the park. The park and nearby Black Diamond Mines Regional Preserve mark the northern extreme of the range of [[Coulter pine]] (''Pinus coulteri''). This species may be seen along the Coulter Pine Trail near the north (Mitchell Canyon) entrance.

In 2005 the [[endangered species]] [[Mount Diablo buckwheat]] (''Eriogonum truncatum''), thought to be extinct because it had been last seen in 1936 and its habitat had been overrun by introduced grasses, was rediscovered in a remote area of the mountain.<ref>{{Cite web |title=05.24.2005 - Dainty pink Mt. Diablo buckwheat rediscovered |url=https://newsarchive.berkeley.edu/news/media/releases/2005/05/24_buckwheat.shtml |access-date=2025-03-18 |website=newsarchive.berkeley.edu}}</ref>
<gallery>
File:Pinus sabineana 00057.JPG|This ''[[Pinus sabiniana]]'' (foothill pine), the most common tree species in the park, is dwarfed by harsh conditions near the summit of Mount Diablo.
File:Pedicularis densiflora mt. diablo.JPG|''[[Pedicularis densiflora]]''
File:ARctostaphylos auriculata at Mt. Diablo - Flickr - theforestprimeval (15).jpg|''[[Arctostaphylos auriculata]]''
File:Juniperus californica Mount Diablo.jpg|''[[Juniperus californica]]''
File:Western wallflower.jpg|''[[Erysimum capitatum]]''
File:Valley Oak Mount Diablo.jpg|''[[Quercus lobata]]''
File:Delphinium nudicaule.jpg|''[[Delphinium nudicaule]]''
</gallery>

===Wildlife===
{{Refimprove|section|small=y|date=March 2025}}
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 [[coyote]], [[bobcat]], [[black-tailed deer]], [[California ground squirrel]]s, [[fox squirrel]]s and [[grey fox]]es; many other mammals including [[mountain lion]]s are present.  It is a chief remaining refuge for the [[threatened]] [[Alameda whipsnake]], [[California red-legged frog]]. Less common wildlife species include the reintroduced [[peregrine falcon]], [[ringtail cat]]s, and to the east [[American badger]]s, [[kit fox#Subspecies|San Joaquin kit fox]], [[roadrunners]], [[California tiger salamander]], and [[burrowing owl]]s.  There are also exotic (non-native) animals such as the [[red fox]] and [[opossum]], the latter being North America's only [[marsupial]].

In September and October male [[tarantula]] spiders can be seen (''[[Aphonopelma iodius]]'') as they seek a mate. These spiders are harmless unless severely provoked, and their bite is only as bad as a bee sting. More dangerous are [[Latrodectus|black widow spiders]], far less likely to be encountered in the open.

In the wintertime, between November and February, [[bald eagle]]s and [[golden eagle]]s are present. These birds are less easily seen than many raptors; golden eagles, particularly, fly at high elevations. Mount Diablo is part of the Altamont Area/Diablo Range, which enjoys the largest concentration of golden eagles anywhere. In recent years there have been credible sightings of California condors, which have been reintroduced at Pinnacles National Park, located to the south in the Gilroy-Hollister area.

A potential hazard is [[Crotalus oreganus|Northern Pacific rattlesnake]]. While generally shy and non-threatening, they are often found warming themselves in the open (as on trails and ledges) on cool, sunny days. Other wildlife to avoid include fleas, ticks and mosquitoes.

There has also been an increase in the [[cougar|mountain lion or puma]] (''Puma concolor'') population in the larger region and one should know how to respond if these animals are encountered. Please see the [[Cougar#Attacks on humans|''mountain lion safety tips'']] in the [[Cougar|mountain lion]] article.

Although [[tule elk]], an elk subspecies found only in California, were historically native to the Mount Diablo Region, they were hunted to extinction by 1850.<ref>{{cite journal |title=A review of considerations for restoration of tule elk to the San Francisco Peninsula and northern Monterey Bay counties of California |author=Richard B. Lanman, William C. Leikam, Monica V. Arellano, Alan Leventhal, Valentin Lopez, Ryan A. Phillips, Julie A. Phillips, Kristin Denryter |journal=California Fish and Wildlife Journal |year=2022 |volume=108 |issue=3 |pages=62–93 |doi=10.51492/cfwj.108.14 |doi-access=free }}</ref> Northwards expansion of Diablo Range elk to Mount Diablo has been blocked by [[Interstate 580 (California)|Interstate 580]].<ref name=Connor>{{cite journal |title=Habitat suitability assessment for tule elk in the San Francisco Bay and Monterey Bay areas |author=Thomas Connor, Thomas J. Batter, Cristen O. Langer, Jeff Cann, Cynthia McColl, Richard B. Lanman |journal=California Fish and Wildlife Journal |year=2023 |volume=109 |page=e19 |url=https://journal.wildlife.ca.gov/2023/12/29/habitat-suitability-assessment-for-tule-elk-in-the-san-francisco-bay-and-monterey-bay-areas/ |accessdate=February 16, 2024}}</ref> In 2006 a bull elk swam {{convert|4|mi|km}} across [[Suisun Bay]] from the [[Grizzly Island]] herd to Contra Costa County, and historically large herds crossed the [[Carquinez Strait]].<ref name=Connor/>

<gallery>
File:Elanus leucurus 3.jpg|[[White-tailed kite]]
File:AWonder Pacific Chorus Frog 001.jpg|[[Pacific tree frog]]
File:Diadophis punctatus 3.jpg|[[Ring-necked snake]]
File:Aspidoscelis tigris munda.jpg|[[Western whiptail|Western whiptail lizard]]
</gallery>

==Facilities==

[[File:Mtdiablo01.jpg|thumb|right|Summit-building roof promenade and beacon tower, Mount Diablo, constructed by [[Civilian Conservation Corps]], 1939–42]]
Entrance stations are located at the end of Northgate Road (in [[Walnut Creek, California|Walnut Creek]]) and Diablo Road (in [[Danville, California|Danville]]).  The Danville entrance is also known as Southgate. If the entrance stations are not operating, park fees may be paid at the junction ranger station, where the two roads join.

From here the road reaches the summit of the mountain, where there is a visitors center housing an observation deck and natural history exhibits. From the elevation of the lower lot the Mary Bowerman Trail is a level wheelchair-accessible path and boardwalk with interpretive stations that extends part way around the mountain; a regular single track trail completes the loop.<ref>{{cite news |url=http://www.savemountdiablo.org/DiabloWatch/2007SpringDiabloWatch.pdf |title=Mary Bowerman Trail |publisher=SaveMountDiablo.org |page=3 |newspaper=Diablo Watch |date=Spring 2007 |access-date=November 15, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20080704165453/http://www.savemountdiablo.org/DiabloWatch/2007SpringDiabloWatch.pdf |archive-date=July 4, 2008 |df=mdy-all }}http://www.savemountdiablo.org/downloads/about_founder_Interview_of_Mary_Bowerman.pdf {{Webarchive|url=https://web.archive.org/web/20151117020345/http://www.savemountdiablo.org/downloads/about_founder_Interview_of_Mary_Bowerman.pdf |date=November 17, 2015 }}</ref> There are {{convert|520|mi|km}} of [[hiking]] and equestrian trails, some available for [[mountain biking]].

[[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 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.

==Climate==
[[File:Snow on Mt Diablo.jpg|thumb|center|740px|{{center|Snow on the peaks of Mount Diablo, as seen from Walnut Creek in December 2008}}]]
The [[National Weather Service]] maintains a weather station at Mount Diablo Junction, 2,170 feet (661 m) above sea level.  The warmest month at the station is July with an average high of 85.2&nbsp;°F (29.5&nbsp;°C) and an average low of 59.6&nbsp;°F (15.3&nbsp;°C). The coolest month is January with an average high of 55.6&nbsp;°F (13.1&nbsp;°C) and an average low of 39.3° (4.1&nbsp;°C). The highest temperature recorded there was 111&nbsp;°F (43.9&nbsp;°C) on July 15, 1972.  The lowest temperature on record was 14&nbsp;°F (-10&nbsp;°C) on February 6, 1989, and on December 14, 1990. (The ''[[San Francisco Chronicle]]'' reported that the temperature dropped to 10&nbsp;°F (-12.2&nbsp;°C) at the summit on January 21, 1962.) Temperatures reach 90&nbsp;°F (32.2&nbsp;°C) or higher on an average of 36.0 days each year and 100&nbsp;°F (37.8&nbsp;°C) or higher on 3.3 days each year. Lows of 32&nbsp;°F (0&nbsp;°C) or lower occur on an average of 15.4 days annually.{{Citation needed|date=July 2010}}
Annual precipitation averages {{convert|23.96|in}}. The most precipitation recorded in a month was {{convert|13.54|in}} in February 1998. The greatest 24-hour precipitation was {{convert|5.02|in}} on January 21, 1972. The average annual days with measurable precipitation is 65.3 days.

Snowfall at Mount Diablo Junction averages {{convert|1.2|in}} each year. Prior to 2009, the most snowfall observed in a month was {{convert|17.0|in}} in April 1975; that same month saw {{convert|6.0|in}} in one day (April 4, 1975). The greatest snow depth was {{convert|3.0|in}} on January 27, 1972. Measurable snowfall does not occur every year, so the annual average days with measurable snowfall is only .5 days.  Snow is more common in the upper reaches of the mountain. On December 7, 2009, Mount Diablo received a rare snowfall of {{convert|18.0|in}}, more in one day than what is normally received in a decade.<ref>{{cite news |url=http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/12/08/MNMB1B0B19.DTL|title=Rare dusting of snow at low elevations |work=San Francisco Chronicle |date=December 8, 2009 |access-date=December 11, 2009 | first=Kevin | last=Fagan}}</ref>

===Data-collecting note===

The Mt. Diablo Junction weather station is positioned at only about 55 percent of the mountain's height. Temperatures and snow levels are notably different than at the upper reaches of the mountain, where lower temperatures and greater snowfall may have occurred, but simply have not been recorded. Nearby Bay Area mountains, like [[Mount Hamilton (California)|Mount Hamilton]], have their weather stations at or near the summit. This is why recorded snow levels on Mount Hamilton are much higher than the ones recorded at Mount Diablo Junction, even though the difference in height of Mount Hamilton and Mount Diablo is only about {{convert|400|ft|-1}}.

Three conditions are measured at the actual summit, however: wind speed, wind direction and temperature; and are available by an automatic telephone voice response system. Recorded information concerning gate open times, road and pet restrictions, and events is available at another number. These numbers are posted at the park website.<ref>{{cite web |url=http://www.parks.ca.gov/?page_id=517 |title=Mount Diablo State Park|publisher=California State Parks|access-date=November 15, 2015}}</ref>

{{weather box|
|location = Mt. Diablo (near summit), elevation: {{convert|3,337|ft|m|abbr=on|0}}
|single line = yes
|collapsed=yes
|width = 80%							
|Jan high F = 	51.2			|Jan low F = 	37.1	|Jan precipitation inch = 		5.49
|Feb high F = 	50.6			|Feb low F = 	37.2	|Feb precipitation inch = 		5.80
|Mar high F = 	54.9			|Mar low F = 	38.4	|Mar precipitation inch = 		3.88
|Apr high F = 	57.6			|Apr low F = 	40.0	|Apr precipitation inch = 		1.57
|May high F = 	66.0			|May low F = 	45.9	|May precipitation inch = 		0.97
|Jun high F = 	74.2			|Jun low F = 	52.0	|Jun precipitation inch = 		0.22
|Jul high F = 	80.9			|Jul low F = 	63.5	|Jul precipitation inch = 		0.07
|Aug high F = 	80.8			|Aug low F = 	59.1	|Aug precipitation inch = 		0.07
|Sep high F = 	78.1			|Sep low F = 	56.3	|Sep precipitation inch = 		0.30
|Oct high F = 	67.2			|Oct low F = 	49.3	|Oct precipitation inch = 		1.67
|Nov high F = 	56.3			|Nov low F = 	41.4	|Nov precipitation inch = 		3.72
|Dec high F = 	50.7			|Dec low F = 	36.9	|Dec precipitation inch = 		4.96
|year high F = 	64.0			|year low F = 	46.4	|year precipitation inch = 		28.72
|source=<ref>{{Cite web
|url=http://www.prism.oregonstate.edu/explorer/
|publisher=Oregon State University
|title=PRISM Climate Group
|access-date=April 18, 2020
}} Input coordinates: 37.8858 N, 121.9154 W.</ref>
}}
{{weather box
|location = Mt. Diablo Junction, elevation: {{convert|2,170|ft|m|abbr=on|0}}
|single line = yes
|collapsed=yes
|width = 80%							
|Jan high F = 	55.5	|Jan low F = 	40.0	|Jan precipitation inch = 	4.77	|Jan snow inch = 	0.5
|Feb high F = 	56.6	|Feb low F = 	40.3	|Feb precipitation inch = 	4.62	|Feb snow inch = 	0.2
|Mar high F = 	59.8	|Mar low F = 	41.8	|Mar precipitation inch = 	3.52	|Mar snow inch = 	0.3
|Apr high F = 	64.4	|Apr low F = 	43.7	|Apr precipitation inch = 	1.63	|Apr snow inch = 	0.4
|May high F = 	70.5	|May low F = 	48.9	|May precipitation inch = 	1.06	|May snow inch = 	0
|Jun high F = 	77.6	|Jun low F = 	54.3	|Jun precipitation inch = 	0.19	|Jun snow inch = 	0
|Jul high F = 	84.7	|Jul low F = 	60.3	|Jul precipitation inch = 	0.01	|Jul snow inch = 	0
|Aug high F = 	84.7	|Aug low F = 	59.7	|Aug precipitation inch = 	0.04	|Aug snow inch = 	0
|Sep high F = 	81.7	|Sep low F = 	57.8	|Sep precipitation inch = 	0.28	|Sep snow inch = 	0
|Oct high F = 	73.5	|Oct low F = 	51.6	|Oct precipitation inch = 	1.42	|Oct snow inch = 	0
|Nov high F = 	61.8	|Nov low F = 	44.5	|Nov precipitation inch = 	3.11	|Nov snow inch = 	0
|Dec high F = 	55.2	|Dec low F = 	39.8	|Dec precipitation inch = 	4.39	|Dec snow inch = 	0.1
|year high F = 	68.9	|year low F = 	48.6	|year precipitation inch = 	25.04	|year snow inch = 	1.5
|source = <ref>{{Cite web
|url = https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?ca5915
|access-date = April 17, 2020
|title = MT DIABLO JUNCTION, CALIFORNIA - CLIMATE SUMMARY
|publisher = [[Western Regional Climate Center]]
}}</ref>
}}

==Art and literature==
[[File:William Keith - Sunset on Mount Diablo (Marin Sunset) - Google Art Project.jpg|thumb|left|Sunset on Mount Diablo by [[William Keith (artist)|William Keith]], 1877.]]
Mount Diablo has inspired many artists and writers. Early work centered on exploration, surveying and was related to the rise and popularization of tourism in the Pacific west. Themes were suggested and heightened by early tourism promoters, the beginnings of the area's preservation and the rise of the environmental movement. The focus was accelerated by artists associated with the [[University of California, Berkeley]], the California College of Arts, the actions of the organizations Save Mount Diablo and the Mount Diablo Interpretive Association, and area art centers, galleries, and museums. In modern times Mount Diablo art has been most strongly represented in plein aire painting, especially the group Artists for Action, and photography.

Representative work includes books and articles by classical writers such as William Brewer, [[Richard Henry Dana Jr.]], [[Alexandre Dumas, père]], [[Bret Harte]], and the Reverend [[Thomas Starr King]], and modern ones such as Mark Allen Cunningham. Poets whose work features the mountain include [[Philip Lamantia]], Andrew Schelling, and Helen Pinkerton.

Early painters include Thomas Almond Ayres, Eugene Camerer, W. H. Dougal, Eduard Hildebrandt, Charles Hittell, [[Edward Jump]], William Keith, [[John Ross Key]], Charles Koppel, Edward Lehman, Pascal Loomis, Henry Miller, Joseph Warren Revere, through Clarkson Dye and others, to modern painters such as Robert Becker, Frank J. Bette, Ruth Breve, Betty Boggess Lathrap, Paul Carey, Bob Chapla, Mary Lou Correia, Ellen Curtis, Pam Della, Susan Dennis, Warren Dreher, John Finger, Pam Glover, JoAnn Hanna, Peg Humphreys, Don Irwin, Jeanne Kapp, Geri Keary, Chris Kent, Paul Kratter, Eunice Kritscher, Fred Martin, Cathy Moloney, Shirley Nootbaar, Charlotte Panton, Greg Piatt, Kenneth Potter, Robin Purcell, Ocean Quigley, Don Reich, Mary Silverwood, Barbara Stanton, Bruce Stangeland, Marty Stanley, and even the recognized comic book painter [[Dan Brereton]].

Photographers include [[Ansel Adams]], Cleet Carlton, Alfred A. Hart, Scott Hein, Stephen Joseph, Don Paulson, Brad Perks, Robert Picker, Richard Rollins, David Sanger, Michael Sewell and Bob Walker.

The mountain has inspired musical artists ranging from the [[Kronos Quartet]] to commissioned works by the [[California Symphony]]. Local pop-punk band [[The Story So Far (band)|The Story So Far]] have a song titled "Mt. Diablo".

The mountain's name is the source for the "Devils" part of the name of the [[Blue Devils Drum and Bugle Corps]], a 17 time Drum Corps International world champion corps, founded and based in Concord, California since 1957.

[[David Brevik]], head of [[Blizzard North]], got the idea for the name of the [[Diablo (series)|Diablo game franchise]] from Mt. Diablo while living nearby.<ref name="Penny Arcade Expo">"To Hell and Back Again:How the Game Industry Has Changed Since Diablo," talk given by David Brevik at Penny Arcade Expo East on March 12, 2011.</ref>

In Marvel Comics, the Black Celestial named Tiamut was imprisoned under Mt Diablo for his crimes against the other Celestials. Arishem and the others sealed him away beneath the Diablo Mountain Range in California. See Fantastic Four Vol 1 #339 and #340.

==Events==
[[File:Mt Diablo Summit Visitor Center.JPG|thumb|right|Aerial view of the summit visitor center showing the renewed aircraft beacon]]
Each Fall the male tarantulas of Mt. Diablo emerge from their burrows to seek mates. The Mt. Diablo Interpretive Association offers guided hikes to observe the migration.<ref name=mdia_tt/> The "March of the Tarantulas" can begin as early as August and last through October.<ref name=ktvu2014/>

Every year since 1964, the Pearl Harbor survivors and their families have memorialized Pearl Harbor Day by relighting the historic Beacon atop Mount Diablo's summit. A ceremony memorializing the [[attack on Pearl Harbor]] on December 7, 1941, is held at the Cal State East Bay Concord Campus, with some of the few remaining survivors who are present. (In 2020, the ceremony was virtual.) This ceremony is made possible due to the support of Mount Diablo State Park, California State University - East Bay: Concord Campus, Save Mount Diablo, CCTV, Vietnam Helicopters Museum, and the Sons and Daughters of Pearl Harbor Survivors.

Under cloudless conditions, more interesting than the sunset itself is the view of the progression of the mountain's shadow across the [[California Central Valley]] from the south to the distant [[Sierra Nevada (U.S.)|Sierra Nevada]] to the north, finally appearing for a few moments above the horizon as a shadow in the post-sunset sky glow.

In April 1946, an Army C-45 transport plane crashed on the north side of the mountain, killing the pilot and co-pilot.<ref>{{cite web |url=http://www.check-six.com/Crash_Sites/Diablo_C-45F_crash_site.htm |title=The Crash of the C-45F on Mt. Diablo |publisher=Check-Six.com |access-date=November 15, 2015}}</ref>

''Save Mount Diablo'' sponsors many spring and fall schedules of events on the mountain, Spring on Diablo and Autumn on Diablo, as well as many other special events, including its anniversary event, Moonlight on the Mountain; Four Days Diablo, a trip on the Diablo Trail; the Mount Diablo Challenge, an annual [[Hill climbing (cycling)|hill climb]]  to the summit with more than 1,100 cyclists each October; and the Mount Diablo Trail Adventure, combined 10k and half-marathon hikes and runs.

The park is popular in winter, when Bay Area residents can enjoy the rare experience of snowfall on the mountain. Snow occurs from the lower reaches of the park all the way to the peak, as was the case in February 2001 and February and March 2006. On Friday, March 10, 2006, an extremely cold storm moved into the region from the [[Gulf of Alaska]], and noticeable amounts of snow fell in all regions of the Bay Area above 500 feet (152 m). The summit of the mountain received around six inches (15&nbsp;cm) of snow at its peak, and the access roads were closed to automobiles at the 3,000 feet (914 m) mark due to the hazardous icy conditions above.

Occasionally there will be public access to astronomical observations made by a local astronomy club. This club was allocated a small parcel on the mountain and developed a permanent observatory at this location. The observatory has a computer-controlled telescope with a CCD camera.<ref>{{cite web | url = http://www.mdas.net/mdoa/mdoa.htm | access-date = August 4, 2013 | title = Mount Diablo Observatory Association, M.D.O.A.}}</ref>

===Mount Diablo Challenge bicycle race===
{{Infobox cycling hill climb
| name = Mount Diablo
| image = Mount Diablo Cyclist.jpg
| image_size =
| image_alt =
| caption = A cyclist riding up Mount Diablo
| location = 
| start = 
| end =
| altitude_m = 
| altitude_ft = 3249
| length_km = 
| length_mi = 10.8
| max_elevation_m =
| max_elevation_ft = 3849
| gradient = 5.7
| maxgradient = 13
| website =
| url =
}}
The Mount Diablo Challenge is a bicycle race held annually on the first Sunday in October and benefiting non-profit, Save Mount Diablo's land preservation programs. The race begins at [[The Athenian School]] at the base of the mountain and climbs {{convert|3249|ft|1}} in {{convert|10.8|mi|1}}. The race typically draws between 800 and 1,100 riders each year who compete in a mass-start format. Bicycle riders of every age and ability are represented in the field, from weekend enthusiasts to top professionals. Prizes are typically awarded to the top overall male and female finishers, along with several age-specific categories. The most coveted prize is the special "One-Hour" T-shirts, awarded to those who finish the climb in less than one hour.

===Course record===

The course record for the Mount Diablo climb currently stands at 43 minutes, 33 seconds, set on October 5, 2008, by Nate English (ZteaM) 4 days after breaking his thumb in a bike accident.<ref name="2008DiabloChallenge">{{cite web |url=http://results.active.com/pages/displayNonGru.jsp?orgID=218713&rsID=70768 |title=2008 Mount Diablo Bike Challenge, Overall Results |publisher=Active.com |access-date=October 6, 2008}}</ref> He broke the 44 minutes, 58 seconds record, set in 2004 by former professional cyclist Greg Drake (Webcor Cycling Team) of Redwood City, California.<ref name="2004DiabloChallenge">{{cite web |url=http://www.doitsports.com/newresults3/client/75181_88473_2004.html |title=2004 Mount Diablo Bike Challenge, Overall Results |access-date=October 8, 2007 |publisher=DoItSports.com |url-status=dead |archive-url=https://web.archive.org/web/20071225050514/http://www.doitsports.com/newresults3/client/75181_88473_2004.html |archive-date=December 25, 2007 |df=mdy-all }}</ref> The previous course record was set by former professional cyclist Mike Engleman (Coors Light Pro Cycling Team) in 1990 with a time of 45 minutes, 20 seconds.

The fastest woman's time recorded at the Mount Diablo climb was set in 2012 by Flavia Oliveira (48 minutes, 13 seconds).  In 2016, Flavia competed at the [[Cycling at the 2016 Summer Olympics|Olympic Games]] in [[Rio de Janeiro]]<ref>{{cite news|title= Brasil define equipe do ciclismo de estrada para os Jogos do Rio 2016|language=pt|url=http://globoesporte.globo.com/olimpiadas/noticia/2016/06/brasil-define-equipe-do-ciclismo-de-estrada-para-os-jogos-do-rio-2016.html|publisher=Globoesporte.com|date=9 June 2016|access-date=10 June 2016}}</ref> where she finished in seventh place.

Outside of the actual Mt Diablo Challenge each October, the climb is one of the more popular uploaded to [[Strava]], with over 11000 attempts recorded as of mid 2014.  The top 10 times listed there are all from the [[Tour of California]], which has used Mt Diablo as a stage several times.  The fastest time (40:49) as of January 2021 is held by professional cyclist [[Lawson Craddock]] set in May 2013.<ref name=strava/>

== In popular culture ==
[[File:Mount Diablo - California - Memorial Marker.jpg|thumb|Mount Diablo Memorial Marker inside summit visitor center]]

* In ''[[Grand Theft Auto: San Andreas]]'', a mountain range known as ''Mount Chiliad'' was based on Mount Diablo. It reappears in ''[[Grand Theft Auto V]]''.
* The silhouette of the mountain was used for the cover art of the books ''[[PiHKAL]]'' and ''[[TiHKAL]]'' by [[Alexander Shulgin]].
* In the book ''[[The Lost Hero]]'' by [[Rick Riordan]], Piper McLean's father is captured and held captive on the summit of Mount Diablo by the giant Enceladus.
* The pop-punk band [[The Story So Far (band)|The Story So Far]] have a song named after the mountain on their [[Under Soil and Dirt|debut record]].

== Notable people ==

[[James "Grizzly" Adams]] was a frequent visitor and resident on Mount Diablo in the mid-1850s.<ref name=cchs />

[[Bob Jones (third baseman)|Robert Walter "Bob" Jones]], the first professional baseball player from Contra Costa County, was born in the "Jones House" in Irish Canyon in 1889, a acquisition project of Save Mount Diablo.

The Mount Diablo Ranch, or Diablo Ranch, was owned by Robert Noble Burgess, who founded the community of [[Diablo, California|Diablo]] and built the mountain's first auto roads.{{Citation needed|date=March 2025}}

On May 24, 1928, the Mount Diablo Ranch, or Diablo Ranch, ownership by Walter Paul Frick<ref name="CCG19370719.1.3">{{cite news |title=Frick Probate |url=https://cdnc.https://en.wikipedia.org/w/index.php?title=Mount_Diablo&action=submitucr.edu/?a=d&d=CCG19370719.1.3&e=-------en--20--1--txt-txIN-------- |access-date=30 March 2025 |work=[[Martinez News-Gazette]] |date=19 July 1937 |page=3 |format=|via=cdnc.ucr.edu — [[California Digital Newspaper Collection]]}}</ref>), a millionaire, who lived in Diablo, {{convert|2250| acres}} from Mt. Diablo Development company, for $50,000, was announced.<ref name="OT19280524.1.8">{{cite news |title=Oakland Man Is Sole Owner of Mountain |url=https://cdnc.ucr.edu/?a=d&d=OT19280524.1.8&e=-------en--20--1--txt-txIN-------- |access-date=30 March 2025 |work=[[Oakland Tribune]] |date=24 May 1928 |page=8 |format=|via=[[California Digital Newspaper Collection]]}}</ref>

Walter Paul Frick was important in the creation of the State Park in 1931, including sale of six of the first seven parcels for the new park.{{Citation needed|date=March 2025}}

Jazz pianist [[Dave Brubeck]] grew up on Brubeck Ranch near the park's North Gate entrance.{{Citation needed|date=March 2025}}

The area for the {{convert|6500|acre|0|adj=on}} Blackhawk Farm, including the mountain's southern Black Hills, was acquired from Burgess and created by Ansel Mills Easton, the namesake uncle of photographer Ansel Adams. Eventually nearly two-thirds of the farm was added to Mount Diablo State Park.  The remainder was developed as the community of [[Blackhawk, California|Blackhawk]] by resident developer [[Ken Behring]] and his partner [[Ken Hofmann]].{{Citation needed|date=March 2025}}

==Legends and folklore==

Mount Diablo has long been the site of numerous reports pertaining to [[cryptozoology]], [[ghost|hauntings]], [[Will-o'-the-wisp|mysterious lights]], and various other [[Forteana#Fortean phenomena|Fortean phenomena]] (it is rumored that the name "''Mount Diablo''" is derived from the propensity for such weird events to be alleged at, or in the immediate vicinity of, the mountain).  [[Phantom cat|Phantom]] black "[[Black panther|panthers]]" are seen with unusual frequency on the slopes of the mountain, as well as at the "''Devil's Hole''" region of the [[Las Trampas Regional Wilderness]].{{citation needed|date=July 2015}}  As early as 1806, [[General officer|General]] [[Mariano Guadalupe Vallejo]] (July 4, 1807 – January 18, 1890) reported an encounter with a flying, spectral apparition, while engaged in military operations against the ''Bolgones'' band of the Bay Miwok tribe.{{citation needed|date=July 2015}}  In 1873, a live [[frog]] was said to be found within a slab of [[limestone]] at a [[mining|mine]] on Mount Diablo.<ref>{{cite book |title=Mysterious America |first=Loren |last=Coleman |author-link=Loren Coleman |year=2007 |publisher=[[Pocket Books]] |page=25 |isbn=978-1-4165-2736-7}}</ref>

==See also==

* [[List of California county high points]]
* [[List of summits of the San Francisco Bay Area]]
{{clear}}
{{stack|float=left|
{{Portal|Biology|Ecology|Geology|San Francisco Bay Area}}}}
{{clear}}
{{stack|float=left|
{{PoI start}}
{{PoI|Mount Diablo|37.881697781|-121.914154997|US| }}
{{PoI|High Sierra mountain peak|37.755|-119.6657|US|Blocks view of [[Half Dome]]}} 
{{PoI end}}}}
{{clear}}
{{stack|float=left|
{{GeoGroup}}}}
{{clear}}

==Notes==
{{reflist|group=lower-alpha}}

==References==
* {{cite web |url=http://www.parks.ca.gov/pages/517/files/mtDiabloBrochure.pdf |title=Mount Diablo State Park Brochure |publisher=California State Parks |year=2000 |access-date=November 15, 2015}}

{{Reflist|2|refs=
<ref name=cchs>
  {{cite web | url=http://www.cocohistory.com/essays-grizadams.html |title=The Strange Mountain Man of Mount Diablo
   | last = Mero | first =  William
   | publisher=Contra Costa Historical Society | access-date=July 18, 2014}}</ref>
<ref name=ktvu2014>
  {{cite news |title=March of tarantulas gets early start at Mt. Diablo
   | url=http://www.ktvu.com/news/news/local/march-tarantulas-gets-early-start-mt-diablo/ngxqG/ | access-date=September 25, 2014
   | last1=Pritchett|first1=Ken | work=2KTVU.com|publisher=KTVU|date=August 7, 2014
   | archive-url=https://web.archive.org/web/20140812042520/http://www.ktvu.com/news/news/local/march-tarantulas-gets-early-start-mt-diablo/ngxqG
   | archive-date=August 12, 2014}}</ref>
<ref name="MDIA">
  {{cite web | url=http://www.mdia.org/mtdiablohistory.htm |last=Adams |first=Seth
   | title=History of Mount Diablo | publisher=Mount Diablo Interpretive Association. Reprinted from: Mount Diablo Review
   | date=Fall 2000 | access-date=July 4, 2010
   | archive-url=https://web.archive.org/web/20071011041930/http://www.mdia.org/mtdiablohistory.htm | archive-date=October 11, 2007}}</ref>
<ref name=mdia_tt>
  {{cite web|last1=Lavin|first1=Ken|title=Tarantula Time
   | url=http://www.mdia.org/site/tarantulas-insects/tarantula-time
   | publisher=Mount Diablo Interpretive Association|access-date=September 25, 2014}}</ref>
<ref name="pb">
  {{cite peakbagger | pid = 1211 | name = Mount Diablo, California | access-date = June 28, 2009 }}</ref>
<ref name=save_md>
  {{cite journal | url=http://www.savemountdiablo.org/downloads/DiabloWatchFall2003.pdf
   | title=The "Eye of Diablo" and the Standard Diablo Tower | year=2003 | issue=36
   | publisher=SaveMountDiablo.org |journal=Diablo Watch | access-date = July 18, 2014}}</ref>
<ref name=strava>
  {{cite web | url=http://www.strava.com/segments/5704921 | archive-url=https://archive.today/20140707023715/http://www.strava.com/segments/5704921 | url-status=dead | archive-date=July 7, 2014 | title=Mt. Diablo: Diablo Challenge | publisher=strava.com | access-date=July 4, 2014 }}https://www.strava.com/activities/1834292</ref>
}}

==External links==

{{sister project links|collapsible=true|wikt=no|q=no|b=no|v=no|voy=Mount Diablo State Park}}

* {{cite web |url=http://www.parks.ca.gov/default.asp?page_id=517 |title=Mount Diablo  |publisher=California State Parks}}
* {{cite web |url=http://www.mdia.org |title=Mount Diablo Interpretative Association}}
* [https://savemountdiablo.org/ Save Mount Diablo land trust and conservation organization home page]
* {{cite web |url=http://www.check-six.com/Crash_Sites/Diablo_C-45F_crash_site.htm |title= Story of the 1946 Crash of an Army C-45F on the northern face of Mount Diablo |publisher=Check-Six.com |access-date=November 15, 2015}}
* [http://home.mchsi.com/~lookout_vistas/Diablo.htm Mount Diablo] and [http://home.mchsi.com/~lookout_vistas/Diablo2.htm Mount Diablo 2]. Panoramic views from the summit of Mount Diablo. Mediacom.

{{Protected areas of California|SP}}

{{authority control}}

{{DEFAULTSORT:Diablo, Mount}}
[[Category:Bay Miwok]]
[[Category:Mount Diablo| ]]
[[Category:Diablo Range]]
[[Category:Mountains of Contra Costa County, California]]
[[Category:State parks of California]]
[[Category:Parks in Contra Costa County, California]]
[[Category:National Natural Landmarks in California]]
[[Category:Native American mythology of California]]
[[Category:Religious places of the Indigenous peoples of North America]]
[[Category:Sacred mountains of the United States]]
[[Category:California Historical Landmarks]]
[[Category:Civilian Conservation Corps in California]]
[[Category:Climbs in cycle racing in the United States]]
[[Category:Gliding in the United States]]
[[Category:Hang gliding sites]]
[[Category:Protected areas established in 1931]]
[[Category:1931 establishments in California]]
[[Category:Landmarks in the San Francisco Bay Area]]
[[Category:Mountains of Northern California]]
[[Category:Mountains of the San Francisco Bay Area]]
[[Category:Parks in the San Francisco Bay Area]]
[[Category:Locations in Native American mythology]]