48 
SANTA MARTA OIL DISTRICT, CALIFORNIA. 
METAMORPHISM OF THE SHALE BY COMBUSTION. 
At many different places in the Santa Maria district and elsewhere 
the oil-bearing shale has been burnt to a pink or deep brick-red color, 
or turned into a hard vesicular rock like scoriaceous lava, as shown 
in PL V, B, p. 36. This metamorphism is due to the combustion of 
the hydrocarbon content. Though the combustion is usually local 
in its effects, the number and wide distribution of the occurrences of 
burnt shale lend importance to the phenomenon. Such altered shale 
is of some value as indicating where the rock has been bituminous 
and where the conditions have favored the occurrence of seepages. 
LOCALITIES WHERE THE SHALE IS AT PRESENT BURNING. 
A number of localities have been observed at which combustion 
is at present or has been in recent years in progress within the Mon¬ 
terey shale. One of these is on the north side of Graciosa Ridge, 
south of the Santa Maria Valley, near the Rice ranch oil well No. 1. 
When this locality was visited by the writers early in the autumn 
of 1906, a fire was burning underground in the shale, causing a smoke 
of disagreeable odor to issue from the surface and making the ground 
hot over an area of many square yards. Oil was oozing up at various 
points near by, and the ground was heated in the neighborhood of 
all these seepages. . The holes from which vapor issued were coated 
with delicate crystals of sulphur. At the point where the burning 
was actually going on and all about in the vicinity, for a distance 
of several hundred feet in some directions, the shale was altered to 
a bright-red color, or baked almost to the hardness of compact igneous 
rock, or rendered vesicular like lava. 
There can be no doubt that this fire was supported by the bitu¬ 
minous material in the shale, and it was probably started by brush 
fires, though these had occurred a good many months before, as 
shown by the new growth of the bushes. It was said that there 
was a brush fire about January 1, 1906, which started the fire in the 
shale, and that futile attempts to put it out by dumping dirt to 
smother it had been made ever since that time. It seems likefy, 
however, that this same fire has been in progress for several years. 
This likelihood is borne out by other accounts. It is stated that 
sometimes during the course of brush fires on the hills sudden darts 
of flames may be seen at night from a considerable distance—the 
result of the setting on fire of gas escaping from the rocks. 
Other cases of burning in the shale have been observed in recent 
years at the San Marcos ranch in the Santa Ynez Valley, and at the 
mouth of Rincon Creek, on the coast near Santa Barbara, as de¬ 
scribed by H. C. Ford. a The phenomena exhibited resemble those 
a Bull. Santa Barbara Soc. Nat. Hist., vol. 1, No. 2, October, 1890. 
