topography ana lUiie X^ones of Oregon 



TOPOGRAPHY 



OREGON has a varied topography, rich in plants, animals, and birds. In 

 its approximately 96,000 square miles of land and water area it offers 

 many fascinating problems to the biologist or geologist, no matter what 

 particular group or specialty of behavior or distribution may absorb his 

 attention. In order to present something of the picture of the State and 

 give a basis for an understanding of the distribution of its bird life it will 

 be necessary to discuss, in a general way, geological formation, present 

 topography, and plant and animal distribution, as all of these factors 

 play an important part in the distribution and abundance of the bird 

 population. 



The State is roughly a rectangle, approximately 350 miles east and west 

 and 300 miles north and south. If the mountain peaks and ranges were 

 graded down to fill the canyons and valleys, it would be found that 

 generally the eastern edge would be tilted upward with the western rim 

 at sea level on the shores of the Pacific. Topographically, Oregon is cut 

 into sections by various mountain ranges, chief among which is the 

 Cascade. Paralleling the coast, about 100 miles inland, from the Colum- 

 bia River to the California line, this great range is the dominant physical 

 feature of the State. In fact, it might with propriety be called the back- 

 bone of Oregon. It has the highest general elevation of all the mountains 

 of the State, and its crest is dominated by a series of huge volcanic cones 

 that rise along its summit in solitary cloud-piercing grandeur. This has 

 a profound effect on climate and rainfall, a feature that will be discussed 

 later. 



The Coast Range (Plate i, A), as the name implies, is never far from 

 the Pacific Coast and in places even jut into the ocean itself in great head- 

 lands that have been beaten away by the ceaseless pounding of the waves 

 to form groups of pinnacles and arched rocks. These are now the homes 

 of myriads of sea birds that find secure nest sites on inaccessible spots 

 (Plate i, 5). The general elevation of the summits is low, the highest 

 point, Mt. Bolivar, southeast corner of Coos County, having an altitude 

 of 4,2.97 feet. The formation, more ancient than that of the Cascades, is 

 weathered down to rounded knobs and ridges that are now all clothed 

 with dense vegetation. On the western slope are numerous small rivers 

 and streams that empty either into small bays or directly into the Pacific. 

 South of the Columbia River the range is cut only by the Umpqua and 



