Description of the Snoqualmie Quadrangle

DESCRIPTION OF THE SNOQUALMIE QUADRANGLE By George Otis Smith and Frank Cathcart Calkins. INTRODUCTION. a proper introduction to the more detailed descrip a natural division line separating the eastern and streams have deeply incised their canyons. In tion of the geology of this quadrangle. western slopes as distinct topographic regions. A the highest parts of this plateau dissection has Location and area. The Snoqualmie quadrangle The oldest rocks known in the Northern Cas more obvious topographic subdivision of the area attained an extreme degree of maturity, while is bounded by meridians 121° and 121° 30' west cades are probably of Paleozoic age and repre is made by the broad .valley of Yakima River, other portions of the upland surface apparently longitude and parallels 47° and 47° 30' north lat sent volcanic products as well as sediments. Their which extends southeastward from Snoqualmie have to a large extent escaped attack. itude, and embraces 812.4 square miles. The quad characters indicate that the conditions of volcanism Pass to the eastern edge of the quadrangle, sepa In the southern half of the quadrangle the rangle is situated nearly in the center of the State and of sedimentation were remarkably similar to rating it into two elevated regions of nearly equal mountains are of a more subdued type. Steep of Washington and includes portions of Kittitas, those that prevailed during the same period in the area, which present marked differences in topo cliffs border some of the streams for short dis Yakima, Pierce, and King counties. Sierra Nevada and in British Columbia. No early graphic character. tances, but are exceptional east of the divide. Natural divisions of the State. The State of Mesozoic strata are known in this region, but during The highest peaks in this quadrangle are in the Even in their highest parts the ridges have broad Washington comprises five natural divisions, which late Mesozoic time sediments that formed sandstones extreme northern and southern parts. One of the level crests, which are taken advantage of by the are geologically as well as geographically distinct. and other rocks were laid down in portions of the "Needles" north of Glacier Lake has an altitude of principal trails. The southern part of the quad The first of these divisions is the Olympic Moun Northern Cascade area. The most important body 7512 feet, and 15 miles east of this point, at the rangle thus lacks the scenic beauty of the northern tains, which overlook the Pacific. These form of Cretaceous rocks lies near the international head of Camp Creek, an elevation of over 7000 part, and when viewed from a distance the south apparently the northern extension of the Coast boundary and represents an extension of the feet is reached on Hawkins Peak, the summit of ern ridges appear to unite in a broad, monotonous Range of Oregon, and are represented farther Cretaceous sea southward from the interior region which is a few hundred yards beyond the eastern plateau that slopes gently eastward and westward north, beyond Juan de Fuca Strait, by the heights of British Columbia. Toward the south the near edge of this quadrangle. The next highest ele from its central portion. of Vancouver Island. est known area of rocks of similar age is in the vations are near the southeast and southwest The valley of the upper Yakima, which has been East of the Olympic Mountains is the second John Day basin and the Blue Mountains of corners of the quadrangle, where the culmi taken as a division line between two topographic division, the Puget Sound basin, a notable depres Oregon. Thus central Washington may have nating points on two ridges are 6312 and 6325 provinces, is itself a conspicuous feature of the sion lying between parallel mountain ranges, and been in Cretaceous time a land area, with seas feet respectively. This distribution of the most relief. The Yakima is remarkable in that its extending beyond the boundaries of the State, both to the north and to the south. elevated points is noteworthy, since, with the low-grade valley extends well back to its head southward in the Willamette Valley of Oregon The deposition of the Cretaceous rocks seems to exception of the highest peak, they are not on waters, an easy railroad grade being maintained and northward in the sounds of British Columbia. have been followed by an epoch in which these the main divide and two of them are many to within 3 miles of Snoqualmie Pass. For a dis Its characteristic topography and geology are and older rocks were folded and uplifted. Thus miles east of that divide. The topographic map tance of 10 miles this valley approximately paral described in the Tacoma folio. was an early Cascade Range outlined, although it clearly shows that the most prominent mountain lels the main Cascade divide, which at Stampede The third division is the Cascade Range, a may be that the range had an even earlier origin. ridges in this region trend not north and south Pass is only about 1 mile distant from the edge of mountain mass trending north and south and The post-Cretaceous mountain growth was accom but more nearly east and west. The high coun the valley. The divide is here generally low and forming the most prominent topographic feature panied by intrusions of granitic and other igneous try in the northern portion of the quadrangle possesses little importance in the topography of the of the State. This line of uplift is a continuation rocks, which now constitute a large part of .the is deeply cut by tributaries of the Yakima, so region. of that of the Cascade Range of Oregon, but the mass of the Northern Cascades. During all the that, while the range continuity is not apparent, Yakima Valley is everywhere broad except for a Cascades of Washington deserve further subdivi time that any portion of this area was not covered yet the heights bordering these canyons exhibit few miles above Easton, and within this quadran sion. From Columbia River northward to the by water the rocks were exposed to the vigorous more or less uniformity in altitude. South of gle includes nearly 20 square miles of bottom land. vicinity of Mount Rainier the range resembles attacks of atmospheric agencies. Thus at the the valley of the Yakima the ridges are more A notable feature on the southwest side of the val the Oregon portion, both in topography and in beginning of the Tertiary the Northern Cascade continuous, especially the one between that val ley at Easton is a ridge rising 1600 feet above the geology, in that it consists of basaltic and andes- region appears to have been a comparatively ley and the Naches basin. The physiographic valley floor, behind which is a well-marked narrow itic lavas of Tertiary and later age. A typical rugged country, although not necessarily at a significance of this distribution of the heights valley, drained by branches of Big, Little, and portion of the eastern flanks of this part of the great elevation above sea level. will be discussed under the heading "Historical Cabin creeks, and by an unnamed creek that enters Cascade Range is described in the Ellensburg During the Eocene epoch an extensive estuary geology." Yakima River near Easton. folio. Farther north, however, older rocks appear or arm of the sea occupied the Puget Sound area The group of mountains in the northern part of The valleys of Clealum River and its several in the Cascade Mountains and the topography of and extended well over toward the present axis of the quadrangle forms a part of the important forks have wide, flat bottoms like Yakima Valley, the range becomes more varied. These geologic the range. Other large bodies of water, probably range which extends eastward across the Mount and Naches River is also bordered by broad and topographic distinctions are sufficiently impor fresh, existed in central Washington, and some of Stuart quadrangle and is known there as the meadows in portions of its course. Along the tant to deserve recognition, and on this account these may even have been connected with the Puget Wenatchee Mountains. This line of heights upper valleys in the northern part of the quad the range from the vicinity of Mount Rainier estuary. Thousands of feet of arkose sediments forms the divide between the Middle Fork and rangle, topographic features due to glaciation are northward to the forty-ninth parallel will be were deposited at this time, and in these Eocene the headwaters of the South Fork of Snoqualmie conspicuous. A noticeable example is seen in the termed the Northern Cascades. The application strata are included all the coal beds in the State River and also the divide between Yakima River character of the valley floor in the vicinity of Big of this term beyond that latitude is questionable, that a,re of economic importance. In this period and the West Fork of Clealum River. Here the Salmon Lasac, where numerous channels and basins since there is in this vicinity an abrupt change also began the volcanism that in later epochs became topography is of the boldest type, the divides have been carved in the rock, the county road fol from rugged peaks to more rounded and lower so characteristic of the province. The more exten being generally narrow, and in some places having lowing one of these side channels at some distance ridges such as occur north of the international sive basaltic eruptions, however, occurred in the knife-like crests. Extreme examples of relief of from the river. The valleys of tributary streams boundary.

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