Petrified Forest
Map SatelliteOne of the finest known examples of an ancient forest is preserved at this site. During the late Pliocene this forest was felled, with the trunks running in almost the same direction, by a nearby volcanic eruption or by winds rushing down the slopes of an adjacent volcano. (The vulcanism has been attributed to nearby Mount Saint Helena which is, however, a fold mountain and not volcanic in origin.) The forest was overlaid by a layer of volcanic ash of the Sonoma Formation and, in time, silica from the groundwater replaced the wood structures. The petrified trunks of the redwoods, Sequoia, are, in places, so well preserved that the delicate wood structures can be traced in the stone. The largest tree excavated to date, and portions are still uncovered, is 38 meters (126 feet) long and 1.2 meters (4 feet) in diameter.
Seeds of four other conifers have been found in the sediment: fir, Abies, spruce, Picea, Douglas fir, Pseudotsuga, and hemlock, Tsuga; remnants of other plants include red alder, Alnus, chinquapin, Chrysolepis, tan oak, Lithocarpus, wax myrtle, Myrica, Rhododendron, bay, Umbellularia, and huckleberry, Vaccinium. This association is similar to the present-day redwood forest of the northern California coast and would indicate a Pliocene climate not unlike that of today. There are, however, some survivors of a warmer period found here: chestnut, Castanea, red bay, Persea, and elm, Ulmus, now found only in the eastern and southeastern United States, and the water chestnut, Trapa, now native only in China.
Integrity: Operated as a commercial enterprise, there are trails and buildings on the site. Excavations have not been completed.
Use: Educational, observational. An admission fee is charged.
Ref: Dorf, E. 1930. The Pliocene Floras of California: Sonoma Flora. Cam. Inst. of Wash. Pub. 412, pp. 37-48.
August 1975
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman