found when a shallow pond dries out. This site is also said to 

 contain fossilized Cambrian trilobites. 



Evidence of former glacial Lake Missoula extends to the upper 

 portions of the Clark Fork Basin. On the open, grassy hillsides 

 of Mount Sentinel and Mount Jumbo at Missoula, one can clearly see 

 the wave-cut shorelines of this former glacial lake. About 35 

 parallel benches encircling the hillsides indicate a water level 

 in the lake about 700 feet above the present valley floor. The 

 2,900-square-mile lake formed near what is now the Idaho border 

 when lobes of the vast Cordilleran ice sheet from British Columbia 

 dammed the Clark Fork. The dam apparently was breached several 

 times . 



67 



