Page:An Illustrated History of the State of Oregon.djvu/21

 Cascade range, where the ancient crust was broken by the upheaving forces that lifted the ranges out of their ancient levels. These deposits of sand and pebbles and water-worn rocks register an era when an older sea covered all westward of the Cascade range: certainly, if, indeed, where it is now that range, was not, in common with the Coast Range, deep beneath the waters. It is useless to endeavor to identify these changes chronologically, as creation in its being and in its mutations writes its historic days in millennials of age, and thus puts our conception of time, drawn as it is from human experience and human history entirely at fault.

The volcanic rocks on the western slope of the Cascade mountains, in the Willamette valley and in the Coast Range of mountains, appear only occassionally, and can scarcely be called characteristic. When they do appear they seem to be an overflow westward of 8 great lava output of the Cascade range, or the product of local volcanic upheavals which pushed up the isolated buttes of the upper portion of the valley at a time coeval with the formation of the mountain ranges. They exist mainly in scattered scoriaceous rocks, or in ledges and peaks of columnar basalt, superimposed on sandstone, trachyte, or resting on miocene strata.

Of course, in indicating the forces that formed thie now verdant valley, glacial action must not be forgotten. Far extending moraines and wide glaciated surfaces tell the story of the far-away eras when these mighty ice-plows furrowed and planed down the broken face of the earth’s crust, and smncothed it into its now beanteous vales. The story of their old movements is recorded very plainly on these surfaces, and the relics of their wider existence are yet living in the moving ice-fields of Mount Hood and the other mighty cones of the Cuscade range.

Enough has already been said to indicate to the careful reader that the Cascade mountains are of volcanic formation. The great snow peaks are all volcanoes. They are called extinct, though some of them, notably Mount Hood south of the Columbia and St. Helen’s north of it, are yet smoking, and on the south- ern slope of the former are great masses of heated rocks, and an ever steaming crater. The great summit intervals between these peaks are generally granitic rock, covered with a deep vegetable soil, intermixed with decayed granite. But from these peaks vast streams of molten lava have poured, flowing mainly eastward, and spreading over the entire country between the Cascade and Blue mountains, from a few inches to hundreds of feet in thickness. In fact, there were many successive overflows, as on the broken faces of the cliffs clearly defined lines of stratification are presented more numerous as we approach the great summits that were their fountain. The greatest outflow in Oregon was in the middle of the range, about half-way from the Columbia river to the Klamath plateau, and thence southward and eastward, including the great Modoc lava beds, forever made historic as the scene of the Modoc Indian war. Thence the [sic] iron sea rolled eastward and northward, overlying the whole country, drinking up the rivers, shearing off the forests, and seizing a nightly holocaust of animal life in its devouring maw. For ages, how long no one can know, this great lava plain, first red and hot and simmering, then black and cold, rending itself into deep chasms in its slow cooling, lay out under the stare without vegetable or animal life, almost without springlet or dewdrop, to cool or soften its black and rugged face. The fires of the volcanoes at length burned low. The mountain summits cooled. A few stray clouds floated over the Cascade range. A few drops of rain touched the iron surface of the earth with their imprisoned might. Showers followed. The springs that fountain rivers began to bubble from beneath the cloven lava beds, and search out an open way seaward through their broken chasms. And thus thé changes of the ages went on. The basalts were ground to pow- der in the mills of the streams. The old sur- faces over which the lava had once spread, were cut into valleys, hundreds of feet deep. Fecund Vegetation sprang forth