Community Corner
The Volcanoes of Clayton
Conservation group discovers some little known history about the region's geologic past after purchasing land for preservation along Marsh Creek Road.
Another chapter in the natural history of our landmark Mount Diablo emerged when it was learned recently that the those hilly domes east of Clayton are volcanic.
The Contra Costa Times is reporting that the conservation group Save Mt. Diablo learned recently that 7.4 acres of land it purchased along Marsh Creek Road contains hills that were formed by magma that pushed up near the earth's surface some 4 to 26 million years ago.
"The result was a series of hilly domes shaped like mushroom caps in a 1-mile-by-4-mile area along sparsely populated Marsh Creek and Morgan Territory roads, between Clayton and Brentwood," the Times said.
Find out what's happening in Concordwith free, real-time updates from Patch.
It would be hard to distinguish those hills from others, if you were just driving by. That's because they are mostly covered with brush and oak and laurel trees.
Mount Diablo itself is not volcanic, though it is home to volcanic rock high up on its slopes, the Times said.That rock comes from eruptions far away in the Pacific Ocean some 165 to 190 million years ago. The mountain itself was formed by plate movements that caused an upthrust of earth layers that was laid on the ocean floor and inland valleys.
Find out what's happening in Concordwith free, real-time updates from Patch.
Save Mt. Diablo purchased the Marsh Creek Road land in July to save it and its habitat of rare plants and wildlife from development. The organization's land programs manager Seth Adams became curious about pinkish crystal rock he found on a lower portion of a dome and consulted geologists who told him something that is not widely known: that 18 sites in the Marsh Creek corridor are volcanic land formations.
"It turns out this volcanic past was right there under our noses all the time," Save Mt. Diablo's executive director Ron Brown told the Times.
Save Mt. Diablo doesn't plan to build a trail up to the dome and will likely restrict access to guided hikes or science class field trips. However, the organization is inviting the public to go along on free hikes today and on Saturday, Oct. 8.
The hikes are from 9:30 a.m. to 1 p.m., and participants should meet at the park-and-ride lot at Peacock Creek Drive and Clayton Road in Clayton. Participants should also RSVP in advanceby calling 925-947-3535.
