136 C. W. Hayes — Expedition through the Yukon District. 



though the floodplain is bordered by gravel bluffs about a mile 

 apart and from 200 to 400 feet high. 



The course of Copper river from the mouth of the Chittenah to 

 the coast is nearly due south. The river has cut through the Coast 

 range a valley which closely resembles that of the lower Taku. 

 Its walls- are high and rugged, and the stream meanders from 

 side to side over a floodplain of coarse gravel. 



Miles glacier, which is the largest of several ice streams tribu- 

 tary to Copper river along its loAver course, has pushed across 

 the valley, forming slack water several miles up the river. The 

 glacier is now retreating, but its northern lateral moraine remains 

 as a dam, over which the river tumbles in a series of rapids. The 

 lake formed by this dam is almost entirely filled with gravel in 

 its upper portion and with fine sand and mud below, so that the 

 water is for the most part only a few inches in depth. 



A short distance below Miles glacier is the head of the delta, 

 which reaches thirty miles southward to the line of bars or keys 

 at the edge of deep water. Excepting a few sand dunes, the delta 

 consists of broad, level meadows and still more extensive mud 

 flats exposed at low tide. Deposition is going on at a rapid 

 rate over this considerable area, and it is interesting to note 

 that subsidence also is taking place. - There are no trees grow- 

 ing upon the delta now, but the remains of many large spruce 

 trees were observed standing several feet below tide-water. 



Vegetation. 



The vegetation of the Yukon basin presents a marked contrast 

 to that of the coast, the luxuriance of which is too well known to 

 require description. This contrast consists more in the amount 

 of vegetation than in the difi'erence of species. Cut off by high 

 mountains from the abundant supplies of moisture which the 

 coast enjoys, the interior supports a comparatively scanty growth, 

 especially of arboreal vegetation, while some of the moisture- 

 loving species of the coast are absent. Excepting surfaces 

 covered by snow or ice throughout the year and the steepest 

 rocky cliffs and screes, practically the whole Yukon basin, as 

 well as the Alaskan coast strip, is covered by a more or less 

 luxuriant growth of moss. Meadows of coarse grass were seen 

 in a few of the interior valleys and some of the gravel terraces 

 along Teslin and Lewes rivers are covered with sage brush, but 



