I shall not say much about the historical geology of Washington
Territory, because it contains some problems which have never been
adequately studied, and which I had no opportunity to investigate. It is
to be hoped that the regular work of the Government Survey may soon be
extended to this important region. Hitherto it has been neglected. A few
able geologists such as Joseph Le Conte, Pumpelly, Newberry, Bailey
Willis, and some others, have made visits to the country on special
errands; but except the treatise of Bailey Willis in Vol. XV. of the
Census Reports, and some brief allusions to the country in systematic
works on general geology, I had nothing to guide me as to the structure
of the country, or the age of its deposits. For all practical purposes,
however, I had no difficulty in understanding the work I had to do.
[Sidenote: The Western Coast regions younger than the Rocky Mountains
and Appalachians.]
[Sidenote: An outlying Continent.]
[Sidenote: The rise of the West Coast.]
All agree that the country west of the Rocky Mountains proper, and
including nearly all of California, Oregon, and Washington Territory,
is geologically younger than the main range, and younger than the
Appalachian country. At the close of the carboniferous period proper,
the Rocky Mountain range constituted a separate continent, with a sea
covering what is now the main Mississippi Valley, including the wide
plains immediately east of the Rocky Mountains, and connecting,
probably, with the polar sea, whilst the Pacific Ocean washed the
western edge of this Rocky Mountain continent; so that until after that
period there were no Wahsatch and Uintah mountains, no Sierra Nevada and
Cascade Range, no Coast Range, and, of course, none of the intervening
country. It is quite possible, however, that there was a third continent
lying west of the present continent in what is now ocean, from whose
waste the sediments were derived which were afterwards elevated and
became the land now included in the three States bordering the Pacific,
whilst the mother continent, which furnished the sediments, sank beneath
the ocean. If there were such an outlying continent, additional force is
given to the views of Dr. George F. Becker, endorsed by Dr. C. A. White,
and to some extent anticipated by Prof. J. D. Whitney, which render it
probable on other grounds that the two great lines of mountains, viz.,
the Sierra Nevada and Cascade Range and the Coast Range, began their
upward movement simultaneously during the early ages of the Juro-Trias.
The rise of these mountain lines was gradual and marked by reverse
movements, whereby, after appearing above the surface, they sank and
rose alternately, receiving fresh sediments, which, especially in the
Washington Territory region and part of Oregon and California, when
above water, became clothed with an enormous vegetation which was packed
into coal-beds, layer after layer. In the lapse of time these all came
above the surface. The mountains grew higher and higher, attended by
intense heat in the axes of the ranges, and at different periods, down
almost to the present, exhibiting volcanic action on an enormous scale.
At other periods, a large portion of the region was visited by
ice-floods, succeeded by water-floods, which top-dressed great areas
with a mingled deposit of gravel, sand and mud, and carried away vast
blocks of the rocky substance of the country, and cut deep channels in
all the highlands.
As Washington Territory is now presented to us, it exhibits a scene of
mountains, lowlands, and elevated plateaus, which are full of interest
and variety. Some general account of its topography has already been
given.
[Illustration: LOWER SNOQUALMIE FALLS, 268 FEET HIGH, ON LINE OF
SEATTLE, LAKE SHORE AND EASTERN RAILWAY.]
[Sidenote: The rocks and minerals of the Cascade Mountains.]
The core of these high ranges is chiefly rock originally stratified,
which has been metamorphosed by heat, and perhaps inside of all, with
branches bursting out at various places, are plutonic rocks which have
never been stratified. This is the state of things on the top of the
Cascade Range, near Snoqualmie Pass, as well as on some subordinate
peaks and ranges. On Mount Logan, the Denny Mountain, etc., are large
bodies of syenitic granite whose age I have no means of determining.
Associated with this are quartzites of fine grain, and extremely hard,
porphyries, and serpentinoid and chloritic rocks of different sorts, in
which are imbedded the magnetic iron ores; and also large beds of
crystalline limestone, both fine and coarse grained. Crossing these, at
various angles, are veins containing the precious and base metals.
[Sidenote: The metamorphic rocks of doubtful origin.]
Whether these rocks are Palæozoic or Archæan in their origin, or whether
they are simply the metamorphosed strata of the upper Juro-Trias, or the
lower Cretaceous, is a question for future study. These plutonic and
metamorphic rocks are believed to extend through the mountainous region
lying north of the Columbia River; and they are reported also in the
Coeur d'Alene Mountains. It is quite certain that on both flanks of
the Cascade Mountains we find in their natural state Cretaceous
conglomerates, sandstones, and shales bearing coal, at least in their
upper beds. The deposits on the east side of the mountain have been much
grooved and denuded, until we find only small areas of the Cretaceous
strata on the Yakima and the Wenatchie rivers, and the Peshastan ridge
between, with a patch of the coal-bearing rocks on the Yakima, and
another on the Wenatchie. On the west side of the mountain range, the
Cretaceous and coal-bearing areas are much larger.
[Sidenote: The coal beds.]
The coal deposits of all the Cretaceous regions of the West are regarded
as belonging to the Laramie period which closed the Cretaceous age, and
constitutes a transition period between the Cretaceous and Tertiary. But
I do not regard this question as settled. The inferior lignites of the
Rocky Mountains, and the semi-lignites which constitute the upper beds
of the Washington Cretaceous coal properly belong to the Laramie period;
but to include the underlying bituminous coals in the same group may be
a matter of question. More will be said in reference to these coal beds
under the next head. The Western coal-bearing rocks begin on outlying
mountains, standing at the west foot of the main Cascade Range. These
outlyers are irregular in size, height and direction; but many of them
are 1,000 to 1,500 feet in height, and they are found in groups,
separated by denuded spaces, from the Cascade Mountains to the Pacific
Ocean, and from the Canada line nearly to the Columbia River. The
largest and most important field, however, lies south of the Snoqualmie
River and between Puget Sound and the Cascade Mountains. Some of the
coals found in the most southern part of the field, and on the Coast
Range, are referred to the Tertiary period.
A smaller and wholly undeveloped field lies on the Skagit River, and
another on, and west of Bellingham Bay. Similar beds are found on
Vancouver's Island. Coal-bearing strata are found also on the Chehalis,
Des Chutes, Nisqually and Cowlitz rivers. Whilst some of these southern
and western strata are referred to the Tertiary period, there has been
no systematic study of their geologic relations.
[Sidenote: The volcanic mountains and their great activity.]
It seems to be settled, however, that the lofty volcanic mountains which
form conspicuous features in the scenery of the Cascade Range, were
active in the Tertiary period, and not only built their own crests 9,000
to 15,000 feet high, but inundated much of the surrounding country with
lava to an amazing breadth and depth. In this region, Mount Baker, Mount
Ranier (also called Mount Tacoma), Mount St. Helens and Mount Adams in
Washington Territory, and Mount Hood in Oregon, were the centres of the
grandest operations; and so continued for ages.
[Sidenote: The wonderful cañon of the Columbia River.]
We see gigantic results of this activity in the cañon 1,000 to over
3,000 feet deep, which the Columbia River has cut through this volcanic
matter in its passage through the Cascade Mountains. This volcanic
deposit consists of brown basalt, which in cooling crystallized into
vertical, polygonal prisms, or columns, which have been sculptured by
the weather into endlessly varied forms, beautiful, fantastic, and
grand; altogether presenting a scene, or succession of scenes, for
twenty-five miles, such as can nowhere else be equaled on the American
continent, unless it be near by, on a tributary of the Columbia, the Des
Chutes River of Oregon.
[Sidenote: The great sheets of basalt.]
This great pile of basalt was built up by a succession of overflows of
lava, the joints of which are plainly visible. The basaltic area, though
perhaps thickest here, continues with a thickness of 1,000 to 1,500 feet
up the Columbia for hundreds of miles; indeed the whole plateau, or
prairie country of East Washington, which is a quadrilateral of some 200
miles in diameter, is but a continuation of the great lava-sheet seen at
the Cascades and the Dalles. Through it the Columbia and Snake rivers
have cut deep channels; and other, though shallower channels, have been
cut across the surface of the plateau by departed streams.
[Sidenote: Origin of the rich soil of East Washington.]
Whether the extremely fertile soil which overlies the basalt in East
Washington is a top-dressing of volcanic ashes, or is decomposed basalt,
cannot readily be determined. It cannot be referred to the Glacial
period, as I observed no appearance of drift anywhere except in the
valley of Spokane River. Such a wide spread of lava is not unexampled in
view of somewhat similar overflows now occurring at intervals in the
Sandwich Islands, where lava runs and spreads itself like water. These
Hawaiian flows are mentioned by Captain C. F. Dutton in his report of
the Zuni Plateau.
A ledge of sandstone belonging to the Meiocene Tertiary is visible under
the basalt at the lower cascade in the Columbia River; and a stratum of
iron ore and vegetable matter is found on the Willamette at Oswego,
lying horizontally between great masses of basalt, showing a long
interval between overflows.
[Sidenote: The volcanoes not wholly extinct.]
These eruptions probably continued with diminishing force until near the
present time. It is reported that Mount Hood has sent out smoke or steam
since the settlement of Oregon. The crater of Mount Ranier was visited
by two gentlemen within a few years, and a night spent in its bottom by
the side of a jet of steam. Such, at least, is the account given by one
of them, Mr. Stevens.
[Sidenote: Glacial drift.]
The Quaternary or Drift Period has left abundant, though by no means
universal, traces of its presence. As before intimated, I saw no relics
of it in East Washington, except a deposit of rather small, generally
very small, and well-rounded quartz gravel, thickly strewing, and really
forming, the flats bordering Spokane River. This gravel macadamizes the
streets of the City of Spokane Falls, and the neighboring roads, so as
to make them firm at all seasons. These gravelly bottoms are not
tillable except in a few spots.
The undulating country north and east of Puget Sound is in many places
deeply covered with drift material which shows the effect of both ice
and water. Blocks of partially rounded granite several feet in diameter
are found on the hills around Seattle. This gravel deposit is not often
found on high points, but there is a ridge in the Cascade Mountains,
near Salal Prairie, which is thickly bestrewed at an elevation of 1,000
feet. This, however, was quite exceptional, and may be the lateral
moraine of a local glacier. The deposit around Seattle is not only easy
to cultivate (its soil being a light blue loam), but seems fertile. The
bottom lands are free from gravel.
So much for the general geology.