6 NORTH AMERICAN FAUNA [No. 55 



west side of the Kiger Gorge tell a part of the story of the glacial 

 period. Summer snow banks or ice beds high up on the cold slopes 

 in the old cirques still feed many permanent streams which are cutting 

 sharp V-shaped courses down the valley bottoms to the arid plains 

 below (pi. 3, B). The top of the range is just an inclined section 

 of the desert pushed up to a height where plant life is still more de- 

 pauperate than at lower levels. The peaks are merely the jagged 

 edges of a much-eroded ridge ^with occasional notches cut clear 

 through by the erosive action of ice and water. 



Over the great arid plains both east and west of the Steens 

 Mountains are extensive fields of black and barren lavas, poured 

 out by numerous small and medium-sized craters. Although cold and 

 dead now, many of these craters appear so fresh and vivid as to sug- 

 gest comparatively recent activity. In many places the long streams 

 of wavy and twisted lavas tempt one to feel the rough surface to see 

 if it is still hot. To the student of geology or the tourist it is 

 unnecessary to go to the Hawaiian Islands or farther away than 

 eastern Oregon to study picturesque and fascinating lava fields and 

 craters, cinder cones, or lava caves. 



In many of the older lava flows where the surface had hardened 

 over a long gentle slope, the still molten interior of a fresh stream 

 broke out below, and the liquid interior escaping, left great tunnel- 

 like subways, some of them miles in length, below heavy roofs of 

 solid rock. The Malheur Caves, the Arnold Ice Caves, the Skeleton 

 Cave, the Horse Caves, and the Lava River Cave are well-known 

 examples (pi. 4), but there are many others without name or fame. 



Less attractive, but not less important, volcanic features of the 

 State are the vast deposits of pumice, volcanic ash, and volcanic 

 sand. In places these deposits cover the rocks to considerable depths 

 and form great plains, sandy valleys, or deep sections of canyon 

 walls. Notable among these are the great pumice plain between 

 Crater Lake and the Paulina Mountains, the black-sand valleys east 

 and south of the Paulinas and in various valleys farther east, and 

 the numerous smaller but deep deposits along both sides of the Cas- 

 cades. Such materials have a very practical bearing 1 on soil fertility 

 and secondarily on distribution of plant and animal life. 



Volcanic activity in the State has practically ceased. At present 

 Mount Hood is the only crater giving noticeable signs of remaining 

 activity. Slight fumaroles of gas and steam occur in the old cup 

 near the top of the peak, and at times the steam and sulphur fumes 

 sweep over the summit in stifling gusts. No recent eruptions, how- 

 ever, are known. 



NONVOLCANIC AREAS 



Nonyolcanic areas in Oregon are found in some of the peaks and 

 high ridges of the Wallowa and Elkhom (or Baker) Ranges, in the 

 Siskiyous, in most of the Coast Range country, and in the extensive 

 lacustrine deposits of the older valleys. 



The higher parts of the Wallowa Mountains, while surrounded by 

 the heavy base of lava of the Blue Mountain Plateau, are largely 

 composed of such materials as granite, quartzite, limestone, marble, 

 slate, and other nonvolcanic rocks. In general the topographic con- 

 figuration resembles the Rocky Mountains, and moreover a large 



