Dec., 1908.] 
Rock Terraces. 
401 
A magnificent rock terrace on the east side nearly one and 
one-half miles long lies between the Columbus Fishing Club pond 
on the north, and Fishinger’s Bridge on the south. It narrows 
toward the north, but attains a width of a fourth mile in its 
central and southern parts. The terrace top averages about 
70 feet above the river and has relief of 20-30 feet. The highest 
part is central, and the rock surface descends eastward as well as 
westward, northward as well as southward. South of the central 
higher part a depressed contour surrounds ten acres, and beyond 4 
the depression near the private road occurs a true sink hole. A 
little washed gravel is found on the terrace top, notably at the 
south, but in no abundance. Soil on the terrace top is otherwise 
thin, chertv alluvium. The terrace front is a continuous rock 
bluff, sometimes precipitous. The bluff behind this terrace is all 
of drift; and the rock below the drift is lower than in the terrace 
top, as is revealed by well records and by the absence of rock in 
the ravine east and southeast of the terrace. One well east of 
terrace goes almost 40 feet below the terrace before reaching 
rock. A large alluvial pan of modified drift built upon the 
terrace argues for its age. 
By way of interpretation, it is suggested that before the last 
ice sheet overspread.this region there was a valley lying eastward 
at this point from the present Scioto which had attained a depth 
within 30 feet as great as the present valley; that this valley 
became drift filled, and then the glacial drainage, and subse¬ 
quently the present Scioto, took their course across the drift 
plain. After cutting down for some time and sweeping off the 
drift, the stream found itself on the rock of the terrace, a portion 
of the western side and bottom of the filled valley. Instead of 
sliding eastward into the old valley, the Scioto began down 
cutting in the rock on the western side of its valley, and thus 
carved the present gorge 70 feet deep below the terrace top. It 
has not been determined whether the sink hole mentioned, 
belongs with the post-glacial drainage system or not, but it is 
believed that it was formed before the last ice advance. 
The largest terrace of all lies on the east side of the Scioto, 
begins about three-fourths mile down stream from the large 
storage dam and continues down stream 2\4 miles or practically 
to the big bend in the river, where it turns eastward around 
Marble Cliff to receive the Olentangy. This terrace varies in 
width from a few yards to about 300 yards. At its upper end. 
it rises 25-30 feet above the river, but descends gently southward 
to less than 20 feet above. Some of the terrace top slopes 
toward the river, but north of Fifth Avenue a considerable area 
is quite level and coincides with the rock structure, the bedding 
planes, quite closely, and hence here might be called a structural 
plain. In some places, the terrace top is well mantled with 
