CHAPTER XXXI.
GEOLOGICAL FORMATION OF OREGON.
We owe to Rev. Thomas Condon, of Dalles City, all our real information upon the geology of Oregon, as well as many notes upon its mineralogy. That which we were able to observe for ourselves only corroborated his views. According to Mr. Condon, the Rocky Mountains once formed the western breakwater of the continent, as the Coast Mountains now do. They were forced up by the subsidence of the ocean-bottom, and the consequent upfolding of the earth's crust. The upheaval occurred near the shore-line, but left a narrow strip of the old sea-bed east of the Rocky Range; enough to prove that the upheaval occurred in the Cretaceous period. A large body of salt water was thus isolated, which gradually, by natural drainage, became brackish only, and finally quite fresh. This change is also proven by the nature of the deposits.
After a long interval of quiet, another upheaval took place, occasioned, like the first, by a subsidence of the ocean-bed. At this second folding of the earth's crust, the Cascades and Blue Mountains were forced up, and once more a large body of sea-water was divided off from the ocean, to form great salt lakes, which gradually became fresh. The Blue Mountains formed an island, separating the northern portion of these waters from the southern, which were drained respectively by the Columbia and the Colorado rivers; but not until by deposits of various character the bottoms of these basins became sufficiently elevated.
In like manner, the later upheaval of the Coast Range caused to be inclosed between these mountains and the Cascade Range another immense body of water, which became fresh in time like the older lakes, and with the gradual elevation of the sedimentary deposits was finally drained off like them. That the dates of the formation of these lakes were widely separated is evident from the fossils of each, which indicate the geologic period to which they belonged; the deposits of the Wallamet Valley being the most recent.
In the meantime, vegetable and animal life flourished along the shores of these inland seas, or lakes. There are canyons in Eastern Oregon, fifteen hundred feet in depth, whose walls present a complete and undisturbed record of the geologic periods. First of all in this record is the old ocean-bed of the Cretaceous period, teeming with myriads of marine shells, perfectly preserved in form, though frequently containing, as a mold, a filling of chalcedony or calcareous spar, making specimens of the highest beauty.
Next above the salt-water deposits, come those of the earlier Tertiary periods. In this division, we find the leaf impressions of those grand trees that flourished during ages of tropical warmth and moisture: palms, yew-trees, immense ferns. In some places an oak-leaf, or an acorn-cup, has left its print in the rocks.
Contemporaneous with the palms and ferns were two species of rhinoceros, and three or four species of Oreodon, an animal allied in some things to the camel, and in others to the tapir family. Another animal of a tapir-like appearance, but called by geologists Lophiodon, also lived during this period, and loft his bones—in the muddy lake-margins to become part of earth's history. Also, a peccary of large size, and an animal bearing some resemblance to the horse, called the Anchitherium—found also in France, and in the Mauvais Terres of Nebraska.
Following this age, was one of volcanic action and the outpouring of immense quantities of ashes and lava. By the lava-streams issuing from the Blue Mountains new barriers were raised, dividing the northern portion of the great lake of Eastern Oregon more completely from the southern, which, by reason of superior drainage, was the first to become dry land. The lake on the northern side of the Blue Mountains remaining longest a lake, continued to receive the drift of its shores for a longer period, and consequently offers a more perfect record of the changes which took place through all the Tertiary periods. Several of the strata formed in this lake are of pure volcanic ashes, still rough as pumice-stone to the touch.
Thus, this Middle Tertiary period was closed in violence. Volcanic fire, earthquake-shocks, and molten lava destroyed and blotted out all forms of vegetable and animal life. The ages roll on, and once more living forms of plant and animal haunt the shores of these shallowing lakes. The oak, the yew, the willow, have left their prints in the sedimentary rocks; and the bones of new creations of animal life, such as the camel and the horse, accompany them. But these, too, in turn suffer extinction by violence; the whole country being covered more than thirty feet deep in volcanic ashes. Indeed, deposits of volcanic ashes exist in Eastern Oregon which are one hundred feet in depth.
After a long night of geological darkness, during which there seems to have been a subsidence of earthquake and volcanic outflow, life once more appears upon this portion of the earth in the forms of elephant, ox, horse, and elk; accompanied by such vegetable forms as were suitable for their subsistence. But yet another period of death was to ensue before the frame-work of the present Oregon was perfected. And this time the desolation appears not to have come from fire, but from frost and flood. How long it continued, or what mighty seas of ice moved over the face of the earth, marking the hardest rock with glacial abrasion, none can tell. But to have so clearly written in the rocks of Oregon the geologic history of at least one continent, is most interesting to scientist and amateur alike. So far as can be seen, the Columbia River Valley must become the most desirable field for the student of the earth's history; and also of research into the record of pre-historic man. For here, somewhere hidden in these ancient pages of rock, must be the beginning of man's history preserved, like that of God's other creatures, in tablets of stone.
From the brief sketch of Oregon's geologic history which has been given, it will appear what the agency has been of those glistening white snow-peaks—Mt. Hood, St. Helen, Adams, Jefferson, and all the rest—in forming the Oregon and Washington of to-day. Time was when these mountains belched forth molten lava, and rained hot ashes over many miles of country on cither side. For some reason—perhaps the direction of the prevailing winds—the ashes were chiefly deposited on the eastern side of the range. The volcanoes themselves, in general, stand on the eastern side of the summit of the range. A covering of lava, in the form of basaltic rock, conceals from sight the record we have referred to, except where by the action of water the pages of the book have been cut through from cover to cover—from ocean-bed to overlying basalt.
For a distance of sixty miles east of Dalles this last overflow may be traced, growing thinner and thinner, until it becomes a mere capping on the hills. Underneath it all is sedimentary, except the interruptions, several in number, of the older outflows of lava. It is owing to the large extent to which volcanic ash enters into the composition of the earth and soil of this portion of Oregon and Washington that both earth and water are so often strongly alkaline. It forms a soil inexhaustible in fertility, and particularly adapted to the growth of cereals; but owing to its elevation, and to the depth of the streams below the surface, together with a dry climate, is difficult of adaptation to the uses of the grain-raiser.
Apropos of the geological formation of Eastern Oregon, Mr. J. Wassen writes in the Overland Monthly, for February, 1869, the following:
"Coming from the north-east, the Blue Range of Oregon, the Cascade Range from the north, and the Sierra from the south, blend into or form a vast steppe or table-land of lava and sage-fields, interspersed with a score of lakes, in size varying from five to forty miles in length, and proportionate width. This high separating belt of land and water commences at the Owyhee River, and extends westward to the mountains, running at right angles to the ocean—a length of three hundred miles, and an average breadth of one hundred and fifty. There are three distinct chains of lakes in this district: The eastern, known as the Warner, inclusive of the Harney and Malheur. The second chain of lakes may be called the Goose Lake, including its northern links—Albert, Silver, and other smaller lakes. Goose Lake nestles in the extreme north end of the Sierra, and is the source of Pitt River, the main branch of the Sacramento. This fact has been disputed, owing, perhaps, to the outlet being underground in the drier seasons. The third and last, and larger of the several chains, is the Klamath, embracing Wright and Rhett lakes, farther south. The Warner lakes string along more like a river; and the rapid current, setting north at all times, is suggestive that this line of water is really the outcropping of a long, subterranean stream. The amount of water is apparently more than the natural drain of the country adjacent; and the outline of a great river channel is distinctly traceable to the lakes of Harney and Malheur. The latter, however, are strongly tinctured with the alkaline soil surrounding.
"The variety and great quantity of fish for which the streams feeding these lakes are noted; the myriads of water-fowl of every conceivable species that make these lakes their summer resort, and the countless numbers of deer, antelope, and the larger game, contribute principally to make the district of the lakes, what it surely is, the happy hunting-grounds of the expiring race. They are hardly to blame for the tenacity displayed in its defense; this broad pass in the mountains furnishing the wily savage with a hundred avenues of escape, to the right or left, with his plunder and his life. The shelving shores of the lakes furnished him warm winter shelter, and the great depressions natural trails free from snow in the severest seasons. These trails are carefully flanked at favorable intervals with little bastions and semicircular breastworks of loose stones, mementoes of Indian skill and strategy. Aside from any known or prospective material resource, the district of the lakes, with its dense forests and weird deserts, picturesque mountains and delightful valleys, and silent waters inclosed by perpendicular walls of mysterious formation, must ever be a scene of enjoyment for the tourist and lover of all that is grand, beautiful, and peculiar in Nature."
Thus does the observing traveler confirm the views of the student of geological science. The southern half of Eastern Oregon retains yet some of the features of the undrained lake districts of Oregon and Washington.
That portion of Oregon and Washington which lies west of the Cascades is part of a great trough, extending from the Straits of Fuca to the Bay of San Francisco. It is not, like Eastern Oregon, elevated above the original sea-bed by immense deposits of volcanic matter; but its older rocks are buried from sight by deposits of the Tertiary and post-Tertiary periods.
There is a curious glimpse into the pre-historic record of man given by the fossils of the Wallamet Valley. For instance, the teeth and tusks of the elephant have been found in Linn, Polk, and Clackamas counties, at no great depth below the surface—as in three instances they were discovered by men engaged in digging mill-races, probably from eight to twelve feet in depth. Side by side with this fact, is the one that at a similar depth some rude stone carvings have been discovered, buried in the alluvial soil of the Lower Wallamet, about two miles above its junction with the Columbia, in Columbia County. Stranger still, there has been discovered at a place just at the northern end of Multnomah County, the remains of a camp-fire, with the half-burnt brands lying in position, as if the fire had but just gone out, and buried under twenty-seven feet of alluvial deposit. Equally curious is the fact that in the Nehalem Valley, eight miles back from the coast, and twenty-five feet below the surface, in a place where there is no suggestion even of a possible land-slide, was lately discovered a large knife of pure copper, with a stone handle. Here is a souvenir of the stone and copper age! Shall we ever be able to collect any facts concerning these ancient Oregonians? The paleontologists have here a splendid field to work in.
The work of the volcanoes is also very evident in Western Oregon. The valley of the Lower Columbia, in particular, reveals the immense overflows of lava in its many forms of basaltic rock. In many places, it occurs in solid masses of many feet in thickness; in others, it has assumed the columnar form; and in many more, it is broken into sharply angular fragments, mixed with earth. The fracture in the latter case is foliated—every fresh cleavage showing what appears like the impression of palm-leaves. The most interesting form of basalt occurs in some columns in the high river-banks just below the town of St. Helen. These columns have been brought to view by the gradual process of denudation; and now project only a dozen feet or so of their tops from the incline of the high bluffs. They consist of uniform blocks, of about ten inches in thickness, having six sides—laid one above another so as to appear like a solid pillar. But their great peculiarity is, that each individual block has a similar-sized chip off the lower side, on its north-west corner or angle. With this exception the blocks are flat. Occasionally one gets thrown off, and so the columns never appear at any great height above the earth; but their fragments strew the river-bank for a long distance.
This basaltic outflow evidently came from Mount St. Helen. On any of the sand-bars in the Lewis or the Cathlapootle River, which debouches into the Columbia on the opposite side, are to be found water-rolled fragments of pumice-stone in abundance; and there are seasons of high-water which bring down from Mt. St. Helen by some of its streams—the Cowlitz in particular—so much white volcanic ash as to render the water milky in its appearance. It is somewhat remarkable that while on the Oregon side the basalt covers every stratified rock or sedimentary deposit, on the Washington side the hills are immense deposits of coarse gravel or sand, and water-rolled stones.
About in the central portion of the Wallamet Valley are some gravel beds of no great thickness; while in Washington Territory, along the Columbia and in the Puget Sound region, the soil is gravelly to an extent which renders it almost unfit for cultivation. Did the facilities which the Sound offered for drainage prevent the deposit of soil-making matter during the period of its submergence?
There are evidences, in the elevated beaches of the Oregon and Washington coast, of great changes of water-level over that portion of these countries west of the Cascades. At Shoalwater Bay, for instance, where the action of the surf has undermined large portions of the bluff shore, breaking it off, there are, exposed to the eye of any observer, vertical sections of sedimentary deposit one hundred feet above the present sea-level. Mixed with this deposit, and sometimes occurring in beds, are vast numbers of sea-shells, of the kinds now common to our oceans. The presence of oyster, clam, and other shells, only found in shallow water; as also of trunks of trees, leaves, seeds, and cones—their forms preserved unbroken—proves these fossils to have been deposited quietly in water of no great depth, and to have remained undisturbed since. Granting this apparent fact, the waters in which they were deposited must have stood more than a hundred feet higher than the present level of the ocean; or enough higher than the highest of these deposits to have sufficiently covered them.
Mr. Condon's theory, which we have already adverted to, supposes what is now the Wallamet Valley to have been the basin of a large body of water, to which, in an article in the Overland Monthly, of November, 1871, he gives the name of the Wallamet Sound. The conclusion of that article has this interesting summing up:
"And now, with our amended theory in mind, as a measuring-rod, let us retrace our steps to the lower country—the Wallamet Sound of the olden time. Let the fall of the Columbia River, from this lake-shore east of the Cascade Mountains to the mouth of the Wallamet River, be stated at eighty feet. Our fossil remains on this lake-shore are 250 feet above the present level of its waters, making a total of 330 feet as the depth of those waters above the present surface at the mouth of the Wallamet River. How naturally one looks to the currents of such a vast body of water as the agency competent to the heaping up of that long, sandy ridge, one hundred feet high, through which the river has cut its way at Swan Island, north of Portland. But let us follow it still farther inland. Over where Portland now stands, these waters were 325 feet deep; over Salem, 165 feet; over Albany, 115 feet; over Tualatin Plains, 145 feet; over Lafayette, 170 feet. A narrow strait, over the present valley of the Tualatin River, ten or twelve miles in length, opened westward upon a broad, beautiful bay, extending over the present sites of Hillsboro and Forest Grove, to Gale's Peak, among the foot-hills of the Coast Range. The subsoil of the fine farms of that rich agricultural region, is itself the muddy sediment of that bay. Farther south, over the central portion of the present valley, and lying obliquely across the widest part of that Wallamet Sound, there arose above those waters an elevated island. It extended from a point south of Lafayette to one near Salem, and must have formed a fine central object in the scene. Three or four volcanic islands extended, in an irregular semicircle, where Linn County now is; and the islands of those waters are the Buttes of to-day—Knox's, Peterson's, and Ward's. One standing on the summit of either of these Buttes, with the suggestions of these pages before him, could so easily and vividly imagine those waters recalled, as to almost persuade himself he heard the murmuring of their ripples at his feet—so sea-like, the extended plain around him—so shore-like, that line of hills, from Mary's Peak, on the west, to Spencer's Butte, on the south, and only lost, on the east, among the intricate windings of extended slopes among the foot-hills of the Cascades. How natural would seem to him this restoration of one of geology's yesterdays!
"The shores of that fine old Wallamet Sound teemed with the life of the period. It is marvelous, that so few excavations in the Wallamet Valley have failed to uncover some of these relics of the past. Bones, teeth, and tusks, proving a wide range of animal life, are often found in ditches, mill-races, crumbling cliffs, and other exposures of the sediments of those waters, and often within a few feet of the surface. Did man, too, live there then? We need not point out the evidences of increasing interest the world feels in facts that tend to solve the doubts that cluster around this natural inquiry. A few more mill-races dug, a few more excavations of winter floods—more careful search where mountain streams wash their trophies to their burial under still waters—and this question may be set at rest, as regards that Wallamet Sound. Oregon does not answer it yet."
Oregon has no State Geologist; and so far has been subject to the investigations, chiefly, of one man, Mr. Condon, with the exception of such slight observations as have been made from time to time by the Government explorers for the Pacific Railroad. That it is a field well worthy of scientific research there can be no doubt, nor that it is one which will richly reward the necessary outlay of money.