THE SPOKANE GLACIATIOX 581 



SPOKAXE RIVER AXD PALOUSE RIVER DRAIXAGE 



TiciniUj of Spolmne. — The city of Spokane is built in a valley eroded 

 in the basalt, not more than 10 or 15 miles from the margin of the pla- 

 teau. To the east rise the mountains of Idaho — an older, higher land 

 surface whose embayed and spurred flanks make an irregular contact 

 between mountains and plateau. Moran Peak, about 8 miles southeast 

 of Spokane, is one of many isolated peaks of the older mountains, stand- 

 ing out in the plateau. Eemnants of the plateau extend perhaps 20 

 miles north of Spokane, separa ted by the valleys of the Spokane and its 

 tributaries and terminated on the east and north by higher hills of crys- 

 talline rock. These remnants constitute mesas, such as Pleasant Prairie 

 and Five-Mile Prairie, about 2,400 feet above tide and about 400 feet 

 above the surface of the "Wisconsin valley trains in the intervening val- 

 leys. The summits of these flat-topped hills apparently mark essentially 

 the original surface of the Columbia lava flows. West and south of 

 Spokane the Columbia plateau extends for many miles, interrupted only 

 here and there, near the margins, by island-like hills or mountains of 

 older rock."^ 



Boulders of various crystalline rocks, igneous and metamt^rphic, with 

 characteristic glacially planed, beveled, and striated surfaces, lie scat- 

 tered on the surface of the Columbia plateau about Spokane, extending 

 as far south as the base of Moran Peak and the village of Spangle, close 

 to the base of the Palouse Hills. They have not been found, however, 

 in this maturely dissected countr}^, nor at altitudes much above 2,500 

 feet above tide on the northern slopes of Moran Peak and Mica Peak, 

 east to the Idaho line. 



Outwash gravel deposits* at similar elevations and close to the driftless 

 Palouse Hills are known at Pantops, along the Inland Empire Highway, 

 and elsewhere. The deposit at Pantops is at least 30 feet deep and pos- 

 sesses current bedding with southward dip. It lies on the basalt plateau 

 not more than a mile west of the base of Moran Peak, at an altitud"fe close 

 to 2,400 feet above tide. The gravel in the deposit is not stained or 

 cemented; it looks as fresh as Wisconsin gravel in the Great Lakes re- 

 a'ion. Scattered throuoJi it are hundreds of srranite boulders averao-injr 

 3 feet in diameter, many of them exceeding 10 feet. The gravel is not 

 coarse, there are no cobble phases in it, and the boulders are wholly out 

 of accord with the gravel as a stream deposit. Furthermore, tlie boulders 

 are subangular and shoAv considerable decomposition of the granite on 

 their less-rubbed surfaces. They doubtless are a local contril)ution, de- 



■* Named "steptoes"' by Russell. 



