Geological Survey Bulletin 611 Guidebook of the Western United States: Part A

Beyond milepost 111, west of Oden (see sheet 21, p. 160), the valley between the Cabinet Range on the east and the Selkirk Range on the west is a broad plain. Down this great valley a glacier once forced its way from Canada past Bonners Ferry and extended many miles south along the route followed by the Northern Pacific to Spokane.

SHEET No. 21. (click on image for an enlargement in a new window)

On approaching Sandpoint the railroad skirts the extreme west end of Pend Oreille Lake, but in this part of the lake the shores are generally low, and the view is not so striking as that obtained from Hope. From Sandpoint the mountain slope on the opposite (south) side of the outlet of the lake, by reason of its gentleness and smoothness, is so different from those generally seen along Clark Fork, although composed of the same kind of rock, that it calls for an explanation. This long ridge does not rise abruptly from the water level at its north end, like the mountain slopes on the other side of the lake, but rises gradually to a height of 2,000 feet above the lake. The profile as seen from Sandpoint is represented in figure 32. The explanation of the gentle slope is that the great glacier which once came down the valley from the north and which probably had a depth of more than 1,000 feet, passed far up on the slope of this mountain and possibly completely overrode it. This mass of ice, with its embedded rocky fragments, ground off all irregularities of the mountain side, leaving it a gently inclined slope from bottom to top. The direction of the moving ice is indicated on the diagram by the arrow.

FIGURE 32.—Profile of mountain slope east of Sandpoint, Idaho. Ice moved in the direction indicated by the arrow and scoured the slope smooth.

At Sandpoint the Great Northern and the Spokane & International (Canadian Pacific) railways approach the Northern Pacific, but the Great Northern at its point of nearest approach is 2 miles from the lake and can not be seen from the train.

South of Sandpoint the railway crosses the lower end of Pend Oreille Lake on a steel and concrete viaduct 4,769 feet long. From this viaduct may be obtained, if the day is clear, a comprehensive view of the mountains east of Pend Oreille Lake. The significant feature of this mountain mass is not its height or its ruggedness, but the evenness of its summits, as if the region were a vast plateau. As this is the country through which the westbound traveler has just come, he appreciates that such is not the case, but the mountains are made up of ridges of nearly the same height, the tops of which, at a distance, blend so as to appear like a flat-topped mountain.

The even crests of such ridges and mountains are supposed to have been formed when the land was low lying and in fact nearly a plain (a peneplain).¹ At that time there were no mountains in this region and the surface was as flat as the prairies of North Dakota and probably much nearer sea level.

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¹The constant tendency of almost all natural processes going on at the surface of the earth is to wear away the high land and to reduce the continent toward sea level. As these processes are always at work wearing away the higher points of the land, it follows that in time the surface of the land would be reduced to a plain were there no counteracting forces at work. The forces that tend to interfere with the reduction of the surface of the earth are those that produce movement within the crust, for such movements are almost always accompanied by elevation at some point, and when this occurs the reduction process is of necessity begun anew and carried on all over again. If, however, crustal movements do not occur for a long time, the surface of the earth is reduced nearly to a plain that stands near but not at sea level. Such a surface has been named a peneplain (meaning "almost a plain"). In most regions the process of reduction in the past has been interrupted by the elevation of those particular parts of the crust before the surface was greatly reduced, but in certain places the process seems to have been carried nearly to its limit and a peneplain produced.

If after the formation of such a peneplain the land is uplifted evenly over a wide area, the peneplain, instead of being near sea level, will form an upland or plateau. As such an elevated tract is always vigorously attacked by streams, canyons will soon be cut back from the edge of the plateau or from the mouths of the streams, and, as time goes on, these canyons will reach farther and farther back into the upland and new canyons will be established, until finally all the even surface of the peneplain will be cut away and instead of a plain or peneplain it will be a hilly upland or a mountainous belt, its character depending on the amount of the uplift. Despite the fact that the region has lost its even surface, the hills or mountains will have, for a long time, about the same height, and their summits will be but little below the surface of the old peneplain. In other words, the country is a dissected plateau, but to an observer at a distance the even crest lines of the ridges still appear like the level top of the plateau.

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For some distance after crossing Pend Oreille Lake the railway skirts the base of the mountain on the left (east), and the cuts through the low spurs reveal the granite in many places. On some of these ledges, even from the moving train, glacial striae (scratches in the bedrock made by rock fragments embedded in the ice and forced along under enormous pressure) may be seen. The direction of these scratches is parallel with the railway and shows that the glacier moved up the valley toward Spokane.

The railway crosses the valley, cutting through many knolls of gravel and sand deposited by a stream which flowed from the end of the glacier during the retreat of the ice from its farthest southward extension. Near milepost 24 can be seen on the west a slope of massive granite that has been laid bare by the ice and has been smoothed and rounded by the same agent. Such bosses of rounded rock have been called by the French "roches moutounées" (sheep-back rocks), and this term has now come into common use in this country.

All the indications thus far observed point clearly to the occupation of this valley by the ice. The small lakes which abound in the district afford still further evidence of the presence of a glacier and the consequent rearrangement of all the drainage lines. Cocolalla Lake occupies a depression hemmed in by hills of gravel that was deposited by the ice or by water flowing directly from the front of the glacier. South of Cocolalla the valley is more or less swampy (another indication of a recently established drainage system), and the granite lies on the west. Farther south the granite can be seen on the east side of the track, hence it probably underlies most of the valley; but, if so, it is well concealed in places by glacial drift.

The village of Granite is appropriately named, for the granite is well exposed there. A short distance beyond the station the railway crosses a high bridge over what appears to be a deep, irregular channel scoured out by the ice, and the knobs of granite, scored and rounded, rise about it in all directions. After passing through a small tunnel in this rock, the train emerges into an open drift-covered plain strewn with bowlders of granite broken from the ledges near the tunnel and carried southward by the ice. Many of these bowlders are 20 feet in diameter, and they occur along the track for a distance of 7 miles from the village of Granite.

Although there are many lakes in this general region, they can not be seen from the train for the reason that they are near the margins of the hills, whereas the railway keeps the middle of the valley. From a point near Athol there appears to be an opening in the mountain wall which bounds the valley on the east. In this break lies the upper or south end of Pend Oreille Lake. The lake is easy of access from this direction and small steamboats will take one to almost any place along its shores. Spirit Lake lies on the west side of the valley, and a little farther south is Fish Lake. The largest lakes, Pend Oreille, Hayden, and Coeur d'Alene, are on the east and south sides of the valley. All these bodies of water have resulted apparently from the damming of the lateral valleys by sand and gravel brought down by the glacier.

The Spokane International Railway approaches the Northern Pacific line on the right near milepost 43, runs parallel with it for some distance, and finally goes under it between mileposts 46 and 47, beyond Athol, and disappears on the left. Originally this valley was covered with a growth of scrubby pine and it was not to supposed be suitable for agricultural or horticultural pursuits, but in recent years fruit trees have been successfully grown, and now apple orchards stretch along the railway for many miles. Although the valley is continuous, there is a constriction near Lone Mountain and a division of the drainage. The water north of this place finds its way into the Columbia by way of Clark Fork, whereas that to the south reaches the same trunk stream through Spokane River. Near milepost 51 Lone Mountain is a conspicuous object on the right (west). It rises to a height of about 1,000 feet above the plain. To judge from the bare rocks exposed about its base, the ice has abraded its foot, but whether or not the glacier passed over its summit is an open question.

At Ramsey, a station directly south of Lone Mountain, the railway is double tracked, the eastbound track diverging to the left, to unite again with the westbound track at Rathdrum, the next station to the west. In going westward the train gradually approaches the mountain mass on the right, and at Rathdrum it is only a few hundred feet from the foot of the hill. Here the rock is a schist,¹ but whether the schist is of Archean age and therefore older than the Belt series, or whether it is the Belt, or some younger formation greatly changed, is a question that has not been settled. At Rathdrum the Northern Pacific crosses over a new line—the Idaho & Washington Northern Railway. West of the crossing the railway runs near the hills on the north for a long distance, but on the left it overlooks the valley of Spokane River, which is spread out like a map before the eyes of the traveler. Most of the valley bottom is farming land, but some of it is too gravelly to be of much value for agriculture. The valley is particularly beautiful as seen from a point a little west of Hauser. From Hauser a branch line runs to Post Falls and Coeur d'Alene, at the foot of Coeur d'Alene Lake, and there is steamboat service on the lake and railway connection from its upper end to the Coeur d'Alene mining district,² described below by F. L. Ransome, and thence across the mountains to Missoula.

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¹Schist is a rock in which a parallel or foliated structure has been developed by shearing or by pressure, a process generally accompanied by more or less recrystallization of the material composing it in layers parallel to the cleavage. Schists may have been originally sedimentary or igneous rocks, but if the schistosity is well developed the original character of the rock is generally obliterated.

²The Coeur d'Alene district, whose mines yield about one-third of the lead produced in the United States, and supply, by value, about 85 per cent of Idaho's annual output of metals, lies high on the western slope of that northward prolongation of the Bitterroot Range which is sometimes called the Coeur d'Alene Mountains. It is to turn the flank of this lofty barrier that the main line of the Northern Pacific swings northwestward down the valley of Clark Fork and then westward by Pend Oreille Lake.

From the east the district is served by a branch of the Northern Pacific which leaves the main line at De Smet (change at Missoula) and, following the old Mullan wagon road, crosses the range by a high pass at the head of St. Regis River. From Spokane, on the west, the traveler may choose an all-rail route via the Oregon-Washington Railroad & Navigation Co.'s line around the south end of Coeur d'Alene Lake, or he may proceed by one of three railway lines to the town of Coeur d'Alene, at the north end of the lake, and there embark on a steamer which connects at Harrison with the trains of the Oregon-Washington Railroad & Navigation Co.'s line to Wallace, in the heart of the district.

Were it not for the mines, the Coeur d'Alene district would be nearly as complete a wilderness now as when Mullan constructed his road across the mountains 56 years ago. It contains almost no arable land, and the timber, while good enough for mining purposes, would probably not have been sufficient inducement to bring railways into the region. Mining is the one paramount industry of the district, and upon it all others depend. Approximately 5,000 men are employed in the mines and concentrating works, and the total population of the district is estimated at 12,000.

Wallace, the principal town and the seat of Shoshone County, contains 3,000 people and is situated at the confluence of Canyon and Ninemile creeks with the South Fork of Coeur d'Alene River. This situation and the fact that it is the terminus of the Oregon-Washington Railroad & Navigation Co.'s line from the west and the Coeur d'Alene branch of the Northern Pacific Railway from the east make it the chief distributing point of supplies for the district.

Although the Mullan road passed through what is now the most productive part of the district, 20 years elapsed before anyone realized that the steep, thickly forested hillsides visible from the road concealed great deposits of lead-silver ore. It was not until 1884 that attention was called to the mineral resources of the region by the exploitation of the gold-bearing gravel and quartz veins on Prichard Creek, in the northern part of the district. Discovery of the lead-silver veins on the South Fork of Coeur d'Alene River soon followed, and by 1888 these had overshadowed the gold deposits in productiveness and value. Since 1903 the district has produced considerable copper and of late years increasing quantities of zinc.

The production of Shoshone County (which is practically that of the Coeur d'Alene district) for 1913 was as follows: Gold, $81,749; silver, 9,337,109 fine ounces; copper, 5,097,894 pounds; lead, 296,740,946 pounds; and zinc, 21,415,565 pounds, valued in all at $20,767,410. The total value of all the metals produced in the district since mining began is approximately $262,608,000.

The mines that have been most productive of lead-silver ore during the past few years are the Bunker Hill and Sullivan, Morning, Hercules, Last Chance, Senator Stewart, Standard-Mammoth, and Hecla. The Tiger-Poorman, at Burke, once a large producer, has been worked out. The Standard-Mammoth is also nearly exhausted, but a continuation of the ore body has been found in the adjoining Greenhill-Cleveland mine. The one large copper mine of the district, the Snowstorm, has yielded ore of the gross value of about $11,000,000.

The rocks in which the Coeur d'Alene ores are found belong to the Belt series. These beds in the Coeur d'Alene district have been crumpled into folds and have been intruded by masses of molten material (magma) which, on cooling, solidified as a granitic rock known as quartz menzonite. During or after the solidification of the igneous rock the region was traversed by great cracks or fissures along some of which took place movements amounting to thousand's of feet, producing what the geologist terms faults. In other places, where the disturbance was less, hot solutions, probably connected with the intrusion of the granitic rock, deposited the ores, partly as fillings of open cracks but largely as replacements of the adjacent rock by chemical processes. After the intrusion of the granite and the formation of the deposits of ore, an uneven layer of rock, probably some thousand's of feet in thickness, was gradually removed by the action of weather and streams. This erosion exposed the once deeply buried granite and the ore.

The principal mineral of the lead-silver ores is galena (sulphide of lead) which in this district invariably contains some silver. Other common minerals of metallic luster associated with the galena are pyrite (sulphide of iron), pyrrhotite (magnetic sulphide of iron), chalcopyrite (sulphide of copper and iron), and spilalerite (sulphide of zinc). The characteristic waste mineral of nonmetallic luster associated with galena, that is, the gangue of the ore, is siderite (carbonate of iron).

The ores, as mined, carry, as a rule, from 5 to 50 per cent of lead and from 3 to 45 ounces of silver to the ton. All but the highest grades are concentrated in the district, by milling, to a product containing about 50 per cent of lead and from 15 to 55 ounces of silver to the ton.

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Between mileposts 66 and 67 the railway crosses the line between the States of Idaho and Washington, the exact point being indicated by a sign at the roadside.

The State of Washington has a land area of 66,836 square miles. It was admitted to the Union in 1889. In 1910 it had a population of 1,141,990. Owing to its position on the coast, the first settlement in what is now Washington was made at a comparatively early date. The places to be occupied first were the posts of the Hudson's Bay Co. Of these Fort Vancouver, on Columbia River, established in 1824, was the headquarters; and Forts Walla Walla and Nisqually were outlying posts to the east and north, respectively.

For a number of years the hunting and trapping of fur-bearing animals was the chief occupation, but gradually the forest was cleared away and farms established. From the necessity of getting rid of the heavy forest developed the lumber business, which from the earliest settlement down to the present time has been the leading industry of the State. In 1909 the value of the timber and lumber products was $89,000,000.

Agriculture at first flourished only along the Sound, west of the Cascade Mountains, where rain is abundant; and the eastern, semi-arid part of the State was utilized only for the grazing of cattle, horses, and sheep. Recently much of the land in the Yakima and Wenatchee valleys and along the Columbia has been reclaimed by the construction of irrigation works, and now it is renowned the world over for the quality of the apples produced. In many districts fruit raising has been carried to the extreme, and now there is a tendency to the greater cultivation of alfalfa and grains. One of the most interesting features of the agricultural development of Washington has been the transformation of the lava plateaus of the central and eastern parts of the State into great fields of wheat that stretch for miles without a break. The success of dry farming in this region made Washington one of the great wheat-raising States of the country. In 1909 its yield of wheat was worth $35,000,000, and its forage crops $17,000,000.

Washington produces yearly metals valued at $1,000,000, but the chief mining industry has been and still is the mining of coal. Coal was first mined in 1860 in Whatcom County, and a little later near Issaquah, in King County, but shipment to San Francisco did not begin until 1871. Since that time many mines in several fields have been developed, and the industry of mining grew rapidly until it reached its maximum in 1910. It declined then because Washington coal came into direct competition with the fuel oil of California. It is estimated that 1913 fuel oil replaced 5,000,000 tons of coal in the markets tributary to Puget Sound. The value of the coal mined in Washington in 1913 was $9,243,137.

The products of the State are valued about as follows: Manufactured products (1909), $220,000,000; agricultural products (1909), $103,000,000; mining products (1913), $17,000,000.

Beyond the State line the railway continues along the north side of the valley, but the valley is not so wide as it is farther east. Apple orchards are numerous and in places extend along the track for miles without a break.

Near milepost 76 the hills on the right (north), which are in plain view, take on a different aspect, and a close inspection shows that they are capped by a flat-lying mass of dark rock. This is the Yakima basalt, one of the principal lava sheets of the great Columbia River basalt which, together with that of nearly the same age in the Snake River valley of Idaho, constitutes one of the most extensive lava plains in the world. The lava flooded all of central and southern Washington and large areas in Oregon and Idaho, and the traveler will see little else in the way of hard rocks from Spokane to the east foot of the Cascade Mountains. It flowed against the mountains on the east, and fiery streams extended up the valleys heading in this range. Although some of the lava lies east of Coeur d'Alene Lake, it is uncertain how far it went in the Spokane Valley, for it has been covered by the glacial gravel. The exposure just noted is the first to be seen by a traveler coming from the east.

Between mileposts 77 and 78, west of Irvin, the railway crosses Spokane River, the water of which is so beautifully clear that every object on the bottom is plainly visible. Near this point the military road constructed by Lieut. Mullan crossed Spokane River. This road entered the main valley from the southwest, east of the present city of Spokane, and then extended up the valley to Coeur d'Alene Lake.

West of the railway bridge the surface of the country to the south is littered with large bowlders composed of many kinds of hard rock, which the ice brought down from the north. From their abundance it is supposed that these bowlders mark the point of greatest advance of the ice and are in the nature of a terminal moraine, although no distinct ridge or other characteristic topographic feature has been left in the valley, as is usual at the extremity of a glacier.

Although the basalt covers most of the country in this vicinity, it did not engulf all the hills, for the highest knob on the north, Little Baldy, composed of schist, stood above the molten flood that rolled into this region from the west. The low hills on the left are composed wholly of basalt, which also shows near the river in the outskirts of the city of Spokane. Here it can be seen at close range as the train passes though the deep cuts on its way to the station.¹

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¹Spokane River has been beset by many difficulties in carving its present channel. At the time the great flood of lava inundated the region, there was evidently a deep valley here which was flooded with the molten material. This inundation did not come as one great wave, but doubtless flood succeeded flood with fairly long intervals between until the lava was piled up to a great thickness, nearly obliterating the original channels.

When the outpourings of lava ceased, the water found an outlet in part along the old courses, but in most localities the eruptions changed the face of the entire country, so that the streams were compelled to carve for themselves new valleys in the hardened lava. This process was well along when the great glacier, laden with the rocky fragments it had plucked from the valley walls, swept down the valley. The materials carried by the glacier were distributed by the streams flowing from the ice front and scattered over the entire valley, filling it to the height seen to-day. Thus for the second time the stream was obstructed and its valley greatly modified, but with the disappearance of the ice it again set to work to carve a valley suitable for a stream of its size. Work was begun near its mouth, but gradually its gorge has been extended upstream until the fall, which marks the point where active cutting is in progress, has reached its present position in the city of Spokane. Here the river makes a series of plunges over precipitous slopes of basalt. Originally this formed a beautiful fall as the swirling waters broke against the dark rocks in their downward plunges, but now the stream has been obstructed for the third time by a dam, and the water has been diverted by man for the production of power. The beauty of the falls is gone forever, for in seasons of drought there is scarcely a trickle where once the river leaped and boiled in its mad rush over the jagged rock. To-day the water drives great turbines that generate 30,000 horsepower for municipal uses and for operating mines and mills in the Coeur d'Alene district.

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Spokane (spo-kan') is a division terminal of the Northern Pacific Railway, and is the center of an extensive agricultural and mining region that is frequently referred to as the "inland empire of the West." A settlement was early established at this place, and in 1881 it was incorporated as Spokane Falls, but later the second part of the name was dropped. The city is served by main lines or branches of all the transcontinental railroads crossing the States of Washington and Oregon, including the Canadian Pacific. Fort Wright, one of the more modern military posts of the Government, is attractively situated on the bluffs of the river just below the city limits, but is not visible from the train.

On leaving the station at Spokane (see sheet 22, p. 164) the train runs down the broad valley for some distance, but not within sight of the falls, and then turns to the left up the valley of Latah Creek. Here there are extensive hillside cuts on the left, exposing beds of dark sand and gravel, which were evidently derived largely from the basalt and were washed into this side ravine by floods that came down the main valley. This is evident from the way in which the gravel is bedded.¹

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¹Careful inspection shows that the sand and gravel is cross-bedded and that the cross-bedded layers dip to the south, up Latah Creek. Figure 33 represents the edges of the beds as they are exposed in the side of the cut. This sandy material was deposited as a delta—that is, the material was washed into the side valley, then occupied by a lake, and at first was laid down on the slope AB. The point A marks the surface of the water, above which the material could not be piled. Additional material was carried along the top of the bed A and laid down as a thin layer on the sloping surface AB. This action was continued until the basin of the side stream was filled to the line AC. The main stream was then deprived of this dumping ground, for that was filled to the same height as the river channel, so the gravel was dropped in the main valley, building it up to the height of D. At this new height the process was repeated until the side valley was filled to the line DF and eventually to the highest point the water reached.

FIGURE 33.—Cross-bedding in glacial gravel on Latah Creek 1 mile west of Spokane, Wash.

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The valley of Latah Creek, as well as that of Lake Creek, up which the railway goes, is marked by a number of well-developed terraces that were doubtless formed at the same time as or soon after the formation of the delta described above, and a correct interpretation of their meaning would throw much light on the conditions prevailing at that time, but unfortunately no one has studied them carefully enough to read their history in detail.

The bedrock on all sides is the basalt, which consists either of hard, dense rock that represents the interior of a lava flow or the more scoriaceous material of the upper part caused by the expansion of steam.¹

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¹Molten lava, as it issues from the earth, is always charged with steam. While the lava remains underground the steam can not escape, but when the lava reaches the surface the pressure is relieved and the steam expands and collects in bubbles, which rise to the surface and burst, giving off the clouds of vapor that always rise from a moving flow of lava. Many bubbles, however, can not escape, and they become, as it were, frozen in the upper part of the flow, giving it a vesicular or honeycombed appearance, as can be seen from the train in many places.

Columnar jointing, perpendicular to the cooling surfaces and therefore nearly vertical, is the most universal and striking structural feature of the basaltic flow. The columns vary greatly in size and regularity of form, their diameters ranging from a few inches to 6 feet. Cross sections of the most perfect prisms are as a rule pentagonal (five-sided) or hexagonal (six-sided), and polygons of four, seven, or eight sides are also common. Columns, such as those described above, may be seen in almost every good exposure of the hardened lava.

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FIGURE 34.—Island of gneiss or schist in the lava (Yakima basalt) near Marshall, Wash.

Although the flows of lava were very extensive, either the molten material did not completely engulf the hills composed of older rocks, or the lava that buried them has since been removed, uncovering the schist at the surface over small areas. Such an area can be seen on the left (east) just before reaching Marshall (see fig. 34), and there are other areas farther on. The schist is easily distinguishable by its light color. Such occurrences of old rocks in the midst of the flood of lava are found only near the margins of the lava plain, where the depth of the once molten material was never great or where the underlying surface was particularly hilly.