1918] ROBBINS—BOULDER PARK 495 
South Boulder Canyon and Mammoth Gulch. The two bodies 
of ice no doubt met at the upper end of the Park and filled it to a 
depth of 400-550 ft., as is evidenced by the elevation of perched 
boulders on both slopes bordering the Park. Below Tolland is an 
area of hummocky topography typically morainal. The hum- 
mocks and the depressions between are strewn with rounded 
boulders, so much weathered that all traces of glacial scratches are 
obliterated. Post-glacial stream action has washed away great 
quantities of this terminal moraine. Lateral moraines join with 
the terminal and extend up the valley on the sides of the ridges. 
There is also a very wide and deep morainal deposit at the mouth 
of Mammoth Gulch. A comparatively small amount of it has been 
carried away. At the entrance of South Boulder Canyon, however, 
Ory grassland 
adow- scrub 
ket 
Me 
thie 
o!l2s 
° So 100 (cena 
— 
Meters Meters 
Horizontal Vertical 
_ Scale Sca/e 
Fic. 2.—Profile of Boulder Park along line extending from A to B in fig. 1 
but small remnants of moraine remain. This is undoubtedly due 
to the fact that South Boulder is a much larger stream than Mam- 
moth, and since the retreat of the glacier it has carried away almost 
all of its moraine. 
It has just been indicated that there are two large distinct 
deposits of morainal material in the Park: one below Tolland, the 
other at the mouth of Mammoth Gulch. They probably represent 
the terminals of two distinct glacial bodies of ice belonging to differ- 
ent periods of glaciation. In all instances where investigations 
(1, 4, 7, 8, 9, 23, 26) of the epochs of glaciation have been made 
in the western mountains, there have been two distinct epochs, 
and furthermore, in each case the earlier glacier extended farther 
than the later. 
ORIGIN OF TERRACES.—The foregoing has been given in order 
to make clear the origin of the ponds and terraces which are such 
prominent features of the Park’s topography. Figs. 1 and 2 show . 
