Banded Chert near the Summit
This was taken from the Fire Interpretation Trail, which circles around the main summit, looking northeast toward the North Peak and the Central Valley beyond. The twisted layers of chert are typically less than an inch to a couple inches thick (1 to 5 cm). They were originally laid down in horizontal layers in a deep sea environment. The tectonic activity that eventually brought these deposits back to the surface resulted in their deformation.
Print No. A00-15-4
Mount Diablo Pillow Basalt
On the north flank of the main peak, along the Falls Trail, lies this outcrop of pillow basalt. Like the chert above, this rock type is indicative of an underwater environment, this time associated with undersea volcanism.
Print No. A01-18-9
Franciscan Complex under the Summit Museum
This view was taken from the Fire Interpretation Trail. The rocks on this slope near the summit are graywacke(?) of the Franciscan Complex. The indistinct banding running up the hillside are parallel fractures, not bedding.
Print No. A98-15-6
Rock City Sandstone
The foothills around much of Mount Diablo are tilted beds of the Great Valley Sequence. "Rock City" lies among the southwestern foothills of Mount Diablo. A popular picnicing and hiking spot, the outcrops are dominantly sandstone. As can be seen here under the canopy of an oak, the forces of wind and water have carved into the sandstone, forming everything from pits to caves.
Print No. A00-40-9
Hidden Poppy Field
On the south side of the peak, north of Curry Canyon, this is a view of a poppy field from the canopy of an oak tree during the spring bloom. When, how long, and how vibrant the poppy display will be depends on the precipitation and temperatures during the seasons leading up to the bloom. Poppies favor a sunny location, and therefore are more common in the open fields of the south facing side of the mountain. The poppy is the state flower of California.
Print No. A98-18-9
Mount Diablo Globe Tulip
This was taken from the Fire Interpretation Trail. The yellow globe tulips are about an inch across. This variety of globe tulip is only found on Mount Diablo.
Print No. A00-15-3
Field of Wildflowers
A wide variety of wildflowers are particularly prevalent along the northern flank of the mountain, especially around Mitchell Canyon. These were spotted along the Mitchell Rock Trail on the way to Eagle Peak. This rocky spot is dominated by red paintbrush, yellow sunflowers, and a colorful assortment of mosses and lichens.
Print No. A01-22-10
Oak Crowned by Rare Double Solar Halo
Taken from the North Gate Road, this view to the west highlights a giant oak and reveals a rare double halo. Haloes are formed by the reflections and refraction of sunlight in ice crystals within cirrus clouds in the stratosphere. The outer halo seen here is a common halo formed around the Sun at a radius of 22o. To the right and left of the Sun (blocked out behind the oak) you can see arcs of a rare halo at a radius of about 18o. The bright spots in each halo, seen here to the right and left of the Sun (especially the left side of the outer halo), are called sun dogs, mock suns, or in technical lingo, parhelia.
Print No. A99-19-8
More Images of Haloes
Mount Diablo Manzanita
Taken from Black Diamond Mines Regional Preserve northeast of Mount Diablo, these manzanitas are recognized by their smooth, brick red bark.
Print No. A99-1-7
