B. The Mountains.-- The grand features of the country on the Pacific side of the Rocky Mountain chain, arise to a considerable extent from a general parallelism in the ranges of heights intersecting the country, a fact apparent in the courses of the rivers were the elevations unmarked on a map.
There are three of these north-and-south ranges, the Coast Range, the Cascade Range, and the Blue Mountains. The first lies near the coast, the second, one hundred and thirty miles inland, and the third, three hundred and fifty miles from the sea.
The Cascade Range is much the most extensive of the three, and even rivals the Rocky Mountains in the height of some of its peaks. It may be traced far into California, and north beyond Puget's Sound, retaining throughout a direction nearly parallel with the coast. It constitutes a strong line of territorial demarcation in Western America, separating a coast section from the interior, and forming a barrier to commercial intercourse, excepting along the single great highway, the Columbia. The two sections, moreover, are widely different in character.
This range, though in general over a hundred miles from the sea, approaches the coast at the south near the Gulf of California, and north at Puget's Sound, and obviously because the waters of the ocean in both cases make deep inroads into the land, rather than from a change in the direction of the range. In the course of the six hundred miles from Puget's Sound to the Sacramento, latitudes 50? to 40?, the range contains seven or eight snowy peaks varying from ten to fifteen thousand feet in height, -- three north of the Columbia, and the others south. Commencing at the north, the are, Baker, Rainier, St. Helens, Hood, Jefferson or Vancouver, M'Laughlin or Pitt, and Shasty. To the southward other high peaks range along the Sierra Nevada, whose snowy tops are occasionally seen from Sutter's, sixty miles up the Sacramento. At the pass near the head of the American Fork, Captain Fremont found the height 9,338 feet, which exceeds by nearly two thousand feet the elevation of the South Pass in the Rocky Mountains; and points in the range near by were still higher by several thousand feet. The Sierra appears to extend into the Californian Peninsula.
The main body of the Cascade Range in Oregon, is seldom over five or six thousand feet in elevation. Its heights are therefore but hills in comparison with the lofty cones above enumerated, which rise out of the chain. These towering summits stand in solitary grandeur, wrapped about in perpetual snows.
Off the mouth of the Columbia, at sea, Mount St. Helens may be seen in the eastern horizon. The snows descend with unbroken surface halfway to its base. It is not less than fifteen thousand feet in height, and has been estimated at sixteen thousand. Mount Hood, thirty miles south of the Columbia, is scarcely as elevated, for the black rocks of its summit show through a ragged coat of snow. Yet it is not less majestic. It opens to view from the southern gateway of Vancouver, rising in lofty sublimity above the crouching hills at its base. Mount Rainier, to the east of Nisqually, and Mount Baker farther north, have the same bold features. Mount Shasty is another of these hoary summits. A heavy mist covered the region as we approached it. Gazing up intently for the peak, visible in the earlier part of the day, we barely discovered some lights and shades far above us, which produced, through the indefiniteness of the view, a vision of immensity such as pertains to the vast universe rather than to our own planet. The Cascade Range is, therefore, of interest, not only topographically, but also for the sublimity of its views; and we shall also find, as we proceed, that its economical and geological importance cannot be over-estimated. ...
Twenty-five miles to the southward of the Umpqua Range, we passed a region of hornblende rocks and syenite. Twelve miles farther south, as we approach the Shasty, the rock was granite, and the same was found on the south side. We here deviated from our southerly course, and for fifteen miles followed the banks of the river eastward, passing soon into a region of hornblende rocks, some of which were imperfect syenite. After making about twelve miles of easting, we again turned south, and twenty miles beyond reached a wide prairie. A few outcropping basaltic rocks were crossed as we entered it, and hills, apparently basaltic, were seen to the eastward; but in our course, after travelling ten or twelve miles, we reached a region of granitic hills. A short distance farther south, we crossed what we designated the Boundary Range; it consisted of basaltic sandstone or conglomerate, and waht appeared to be the Astoria tertiary sandstone containing fossils. Southward, the basalt and sandstone run side by side nearly to the Shasty Mountains. Fronting the Shasty Peak, the plain is covered with hillocks of a porphyritic lava, while the hills to the westward consist of sandstone, and then change to serpentine and syenite.
Mount St. Helens and Mount Rainier - eruptions:
... Many a frosted peak stands to attest the former activity of volcanic fires in Oregon. Baker, Rainier, St. Helen's, Hood, and others of the series, have been partially described. These isolated cones so resemble the lofty summits of Mexico, that we cannot doubt, although they have not been ascended, that they once formed a line of volcanoes through the whole extent of Oregon, and far into California. It is reported that St. Helen's and Rainier have shown evidences of action within the three or four years past, * and an account is on record of ashes falling fifty years since. But these centres have not been the sole or even the principal sources of eruption. There are craters in the Coast Range, and others over the interior section. Mount Swalalahos south-southeast of Astoria is one of the former; several summits beyond Fort Hall are among the latter; and many peaks may be added to the number when the country is fully explored. But besides these vents, there have been still wider eruptions from fissures over the country, near the peaks and subordinate to them as well in more distant regions, and from this source extensive beds of basalt or basaltic lava have flowed throughout the land. We have shown, in another place, that fissure eruptions are common in all volcanic regions, (at least in recent periods,) and the same fact is sustained by a survey of Oregon.
* Fremont mentions that on the 23d of November, 1842, ashes were ejected by St. Helen's. -- Rep. Exp. ii. 1842, '43, '44, p.193.
Mount Rainier, Mount St. Helens, and Mount Hood:
... The three peaks of the Cascade Range, Rainier, St. Helen's and Mount Hood, were so far examined by the surveying parties of the Expedition, as to determine that the rocks became more cellular and lava-like as the mountains were approached. Near Mount Rainier, Dr. Pickering found trachytes abundant; over the foot of St. Helen's, the rocks were cellular basaltic lavas; along the Cascades of the Columbia, and on the John Day's and Chutes rivers, which are properly at the foot of Mount Hood, there were similar cellular lavas, as ascertained by Mr. Drayton. It also appears that remains of a crater may be distinguished in the summit of Mount Rainier. These cones have similar features, as already described, and slope at an angle of about thirty degrees. Mount Saint Helen's is quite regularly conical.