Journal of Travels From St. Josephs to Oregon / With Observations of That Country, Together With Some Description of California, Its Agricultural Interests, and a Full Description of Its Gold Mines.

by Riley Root

At the base of the mountain, commences a tertiary deposit of about 20 miles in width, which, with an alluvial deposit of about 20 more in width, to the great rivers of the valley, hides from sight the remaining portion of tilted rocks, so that the entire width of the tilted strata can never exactly be ascertaind. But if a mountain range like the one under consideration, is formd by the furrowd and ridgd condition of the earth’s crust, by conforming to a diminishd molten nucleus within, from refrigeration of its heat, it may be expected that the whole declivity, from its axis or highest point to its lowest or mid valley, may be all of it tilted up in the same manner as that portion which is presented to sight. If this be fact, we are then apprizd that a portion of the earth’s crust must have had a thickness of full 100 miles, by measuring across the tilted rocks, from the central valley, to the top of the mountain, eastward,—a fact not hitherto believd by geologists, from experiments made upon the increase of downward heat, to where the crust must necessarily become molten.

As so many and various opinions of the tilted condition of primary stratified rocks have been advancd among the visitants of the gold district of California, a few conflicting opinions may serve in some degree to satisfy the mind of the curious.

It is the belief of some, that rocks cannot have become tilted without the expansive powr of volcanic agency. Hence, on viewing the country around, they imagine they see successions of craters, formd all over the western declivity of the Neveda mountains, and in some places, profusions of scoria bestrewing the ground. For my own part, I must confess that I have seen nothing in my ramblings to justify a belief that volcanic agency any where has existed so as to produce the present appearance of those rocks.

Those persons imagining volcanic agency in those parts, are not aware that intense heat destroys stratification, for in the middle of the craters of some of their imaginary volcanoes, the stratification is as perfect as in any other portion of the tilted district, and they are not apprizd that in such case a discrepancy must therefore exist.

After the tilting of those rocks had occurd, it would not be improbable, with such an enormous crust resting entirely upon a liquid, molten nucleus, that many undulations in it should occur, and in many instances the crust should become weakend and even sunderd apart by the severe strain. Into fissures so formd, granite, sandstone and conglomerated rocks, may have subsequently been intruded, presenting, therefore, to persons unacquainted with such rocks, the appearances of craters, scoria, &c. In some parts of New England, primary stratified rocks are tilted up confusedly, having no regular line of strike. In some cases, the dynamics employd may have been volcanic, or they may have been paroxysmal, acting from time to time, till those rocks were thrown into their present condition. But tilted rocks that have a regular line of strike, must have a regular agency to place them in such condition. Hence, then, considering the perfect parallelism of the tilted rocks of Golden California with the mountain axis, it seems to follow, that an exceedingly slow and regular movement of the tilting of those rocks must have occurd.

Another consideration of the western declivity of the Neveda mountains, is in relation to the formation of its rivers.

Almost invariably, the rivers of Oregon were formd by an expansive force from beneath, but the rivers of California were formd by undulations in the earth’s crust, which is well proven by the entire passage of unbroken strata across the beds of streams. Such condition of its rocks, is also another proof against volcanic agency in those parts.

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The inquiring mind may now be led to the subject of Quartz Rock, containd among the slate rock of the gold district.

The quartz rock of the gold region is mostly white, though some of it is of the carnelian order, whilst some is translucent, and other specimens are entirely transparent. The carnelian appearance of some of the quartz seems to have been nothing more than the circulation of water containing the red oxide of iron, through the cracks of the broken quartz, till the rock became tingd with it. The transparent variety is crystalizd, and is found only sparingly.