CHAPTER III. 
GEOLOGY OF THE WESTERN RANGE OF SIERRA NEVADA. 
Relations of western range of Sierra NEVAbA to mount sHasta and the siErRa Nevada of California.—General geological 
RELATIONS OF MOUNT SHASTA.— COASTLINE ONCE FORMED BY THE SIERRA NEVADA AND CA3CADE MOUNTAINS—SUCCESSIVE STAGES 
IN THE ELEVATION OF THE CONTINENT —“CONTINUITY OF THE COAST MOUNTAIN'S—TRANSVERSE CHAINS.—LlNES OF FRACTURE 
DIVERGENT FROM MOUNT PITT AND MOUNT SHASTA,—CARBONIFEROUS LIMESTONES OF MOUNT SHASTA, PERHAPS CONTINUOUS WITH THE 
METAMORPHIC LIMESTONES OF THE SIERRA NEVADA—LOCAL GEOLOGY.—TRAP PLATEAUS ABOUT FORT READING.-—CoAL NEAR MeCUM- 
ber’s flat..—Recent volcanic rock around the base of Lassen’s butte—Lassen’s butte a volcanic cone.—Lava plain on 
CANOE CREEK.—CHIMNEYS.—SUBTERRANEAN GALLERIES — TRAP PLATEAUS AT THE MOUTH OF CANOE CREEK. INFUSORIAL MARLS ON 
BANKS OF PIT RIVER.—Beds OF ROUNDED STONES UNDERLYING MARLS.—TRAP FORMING THE WALLS OF THE LOWER CANON OF PIT RIVER.— 
Mountain of metamorphic slate. 
From Fort Heading we passed southward of the limestone mountains mentioned in the last 
chapter, and following a course little north of east, crossed that portion of the Sierra Nevada 
which connects Lassen’s butte with Mount Shasta ; coming down on to Pit river, at the upper 
end of its long canon or series of canons, formed by its passage through this chain of mountains. 
Some differences of opinion have prevailed in reference to the relations which this range sustains 
to the Sierra Nevada on the one hand, and to Mount Shasta on the other ; hut it has been 
generally regarded as a spur of the Sierra Nevada running off at a considerable angle with the 
main trend of that chain to connect with Mount Shasta. It has also been supposed that east¬ 
ward of Mount Shasta the main range of the Sierra Nevada would he found extending northward 
and connecting directly with the Cascade mountains of Oregon. Mount Shasta has even been 
claimed as a portion of the coast mountains, and is so represented by Dr. Trask, ( Geol . Report , 
1853, p. 48.) 
Dr. Trask also suggests that the Sierra Nevada terminates at Lassen’s butte, and that the 
coast mountains, when continued northward, form the Cascades of Oregon and Washington 
Territories. 
Both these hypotheses seem to me untenable. So distinct a line of upheaval connects Mount 
Shasta with Lassen’s butte, and Lassen’s butte with the Sierra Nevada, that they all seem to 
form the inseparable parts of a single mountain system. 
As has before been stated, the geological data are still wanting for determining with precision 
the relative ages of the Sierra Nevada and coast mountains ; hut the evidence, as far as it goes, 
is altogether in favor of the greater antiquity of the Sierra Nevada, and of the connection of 
Mount Shasta with the older system. The most characteristic fossiliferous strata of the coast 
mountains have not yet been found in the Sierra Nevada. 
The physical structure of the country traversed by these mountains teaches the same lesson. 
The Sierra Nevada, including Lassen’s butte and Mount Shasta, form the wall which bounds 
the elevated plateau. The eastern bases of Jthese mountains are four thousand feet above the 
western, and it seems difficult to resist the conclusion that at one stage in the elevation of the 
continent the mountains I have mentioned, with the Cascades of Oregon, formed its western 
