"Those damn biologics! They cover up all the rocks," so said a geological colleague of ours not long ago. And chaparral is by far one of the best covers, no doubt. But when the fire comes, and eventually it will, so goes the cover and the geology is revealed, although a bit darkened by soot.
The Topanga Rock! On Topanga Canyon Road in the Santa Monica Mountains, January 9, 2005. After nearly 16 inches of rain, the boulder fell about 30 feet from its original position. AP Photo/Damian Dovarganes.
Mountain composed of gabbro revealed after the 2003 Cedar fire. Note different granitic formations with white boulders (tonalite) showing on right compared to the reddish, iron rich gabbro. Looking north from Guatay, San Diego County.
Death on the Gabbro. Deep red colors are characteristic of gabbro soils found in Southern California. This little critter chose this place to rest...for good, on the gabbro.
Chaparral ecologist Jon E. Keeley points out the interesting vegetation patterns on Mt. Diablo in the San Francisco Bay area. An edaphic (soil type) influence appears to have a significant impact on what type of plant community dominates certain areas on the mountain.
Magnesium rich serpentine soils (note greenish patches in the mountians) give rise to unique plant communities composed of rare plant species endemic to such environments. Serpentine chaparral is one such plant community.
A close-up of serpentine soil. Notice the green chunks of serpentine, a metamorphic rock found in the coast ranges of northern California. Serpentine is the official State Rock of California.
Ione chaparral is a special type of chaparral found exclusively in the aluminum rich soils near Ione, California.
Some interesting papers on the impact of soils on chaparral plant communities: