48 ONC Ale Jal, JaldlceSwale, JC 
Within several miles of its head, the South Fork of the Salmon 
River has carved a pretty postglacial gorge or tiny canyon in 
the solid rock of the old valley floor. This is twenty to thirty 
feet in depth, has precipitous walls, and is no wider than the 
small stream flowing in it. It abounds in rapids and low 
cascades. 
The Union Creek glacier.—This occupied the next main series 
of high valleys to the east of the Salmon River glacier. There 
was a main trunk five miles in length, and two branches each 
several miles in length. The width was one quarter to one half 
mile, and the thickness of all approximated 1000 feet. They 
headed at about 6500 feet (present altitude), and the main 
trunk descendeds to) 5000) feet of saliitiudes NeamaitsmenGesin 
‘was much contracted, and but little modified the original 
V shape of the valley. Its extent is clearly defined by its very 
bowldery lateral moraines. One of these partly obstructs the 
mouth of a tributary valley, that of Pin Creek, which was not 
glaciated, altho equally as elevated as glacier occupied valleys 
on either side of it. This was because it opened too directly 
toward the sun. 
When recession had proceeded to the extent of dissevering 
the branches of the glacier in the East and West Union Valleys, 
that of the East Union was the most vigorous, and formed a 
beautiful half-looped terminal moraine at the junction. The 
West Union Creek flows swiftly in a shallow ditch cut into the 
very bowldery deposit just outside of the crest of the moraine, 
but transverse to the general slope of the surface. This shows 
that this creek occupied its present course as early as the 
time when the moraine limited the East Union glacier. The 
extremely small amount of erosion accomplished on this steep 
declivity tells of the recency of the glacial epoch in these 
mountains. 
The three Unions have the usual meadows, and are well 
supplied with glacial lakelets. 
The Swift Creek glacier—The characteristic features of this 
member of the glacial series were its length, its descent to a low 
