ABSTRACTS 107 



are nearly as strong as those of the Warren waters in the Genesee 

 region. This beach is specially interesting as being entirely new and 

 unexpected, and indicating a long pause of the waters at an altitude 

 between the Warren and the Iroquois plane, while the correlating out- 

 let is unknown. The body of the paper is a detailed description, for 

 record, of the phenomena of these two beaches. 



Principal Features of the Geology of Southeastern Washingto)i. By 

 Israel C. Russell. 



A brief statement of the results of a six weeks' reconnoissance in 

 the southeastern portion of the state of Washington, made for the 

 United States Geological Survey. 



Practically all of that portion of Washington which lies south of 

 the Big Bend of the Columbia is occupied by a succession of basaltic 

 lava flows. This is a portion of a vast lava-covered region embracing 

 northern California, central and eastern Oregon, central and south- 

 eastern Washington, and southern Idaho. The great fissure eruptions 

 which supplied the Columbia lava, as the basalt is termed, occurred in 

 the Miocene. The Columbia lava in Washington to the west of the 

 Columbia, south of the Big Bend, as ascertained during a previous 

 reconnoissance, is broken by extensive faults and the blocks thus 

 formed variously tilted. In the region here treated, however, the 

 basalt is horizontal over extensive areas, and deeply dissected by 

 Snake River and its tributaries. Many lava sheets, one resting on 

 another, were seen. Between some of the flows there are widely 

 extended sheets of lacustral clay, sand, gravel, volcanic dust, and lapilli. 

 In some instances leaves, and the silicified stumps and trunks of trees 

 occur in these layers. The Columbia lava flowed about the bases of 

 the mountains of eastern Washington and the adjacent portion of 

 Idaho, in a series of inundations which covered the low country to the 

 south. The level basaltic plateau meets the mountains of metamor- 

 phic rock in much the same manner that the sea joins a rugged and 

 deeply indented coast. The lava entered the valleys and gave them 

 level floors of basalt; the deeply sculptured ridges between the valleys 

 were transformed into capes and headlands; outstanding mountain 

 peaks became islands in the sea of molten rock. After the last of the 

 lava sheets was spread out, the rivers flowing from the mountains 

 began the excavation of channels across the basaltic plateau and have 

 deeply dissected it. The most important of these channels is the one 



