[2.8] BIRDSOFOREGON 



Other than this basin drainage and the drainage from the Klamath Basin 

 southward into the Klamath River, all the innumerable streams rising in 

 the Blue Mountains are gathered up by the Columbia-Snake system. 



Geologically, the Siskiyou and Blue Mountains are the most ancient 

 areas in the State. Both are composed of sedimentary rocks of many kinds, 

 and geologists say that in some prehistoric time they stood as two islands 

 in a stormy sea. The Blue Mountains area is particularly rich in fossils, 

 the great John Day beds being part of this formation. 



The Coast Range is adjudged to be the next oldest land, probably 

 rising at one time to greater heights than at present and more or less 

 completely closing off from the open ocean a shallow inland sea. 



The Cascades are the youngest and greatest of the major ranges and are 

 largely volcanic in character. The great sage plains that stretch from 

 their eastern base to the Blue Mountains and on into southern Idaho and 

 northern Nevada were built up by a succession of vast flows of basaltic 

 lavas. These lavas surged up against the Blue Mountains, burying the 

 foothills under a lava cap that, superimposed on the older rocks, is now 

 plainly visible where the rivers have carved their canyons. Much of the 

 basic rock of the Cascades, particularly northward, is of this type. Later 

 came another volcanic period during which the lighter-colored lavas and 

 cinders that form the great series of cones along the backbone of the range 

 were thrust upward through this dark-colored lava. Beginning at the 

 north, those of major importance are Mount Hood, Olallie Butte, Mount 

 Jefferson (Plate 6, A), Three Fingered Jack, Mount Washington, Belknap 

 Crater, The Three Sisters (Plate 6, Z3), Broken Top, Bachelor Butte, 

 Diamond Peak, Mount Thielsen, old Mount Mazama the great caldera 

 that is Crater Lake and Mount McLoughlin (Mount Pitt). In addition, 

 there are innumerable cinder cones and lesser craters where dying volcanic 

 fires dissipated their last energies. 



Sometime later the basaltic lavas were broken by great earth convul- 

 sions into a series of north-and-south faults that extend for miles. Each 

 of these has a steep face, which is almost sheer precipice, and a gentler 

 slope, up which a car may be driven with ease (Plate 7, A). So far as 

 their effect on fauna and flora is concerned, the most important of the 

 faults are the Warner Mountains just east of Lakeview, the fault line of 

 which is most perfectly preserved as the Abert Lake rim; Hart Mountain 

 (Plate 7, B) to the east of Warner Valley in eastern Lake County; and 

 the Steens Mountains, which extend from just south of Malheur Lake 

 almost to the Nevada line. 



LIFE ZONES 



FIELD WORKERS in biology have long known that plants, birds, mammals, 

 and other living forms are to be found grouped in more or less character- 

 istic fashion into communities and associations. Some of these groups and 



