Page:Popular Science Monthly Volume 48.djvu/174

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162
THE POPULAR SCIENCE MONTHLY.

of gravel in the old rock gorge is connected with the Glacial period is clearly shown by the fact that these lower terraces can be followed up the banks of every stream which comes out of the glaciated region to the old ice border, where they emerge into the moraines which were deposited directly by the ice. This is shown in our map, on which a small portion of the glaciated area appears with Big Beaver and Little Beaver Creeks flowing out from it. The gravel terraces at Brilliant and Steubenville are shown

PSM V48 D174 Map of middle ohio river region.jpg

Fig. 4.—Map of Middle Ohio River Region.
Glaciated area, shaded. Terraces shown by dots.

on this, together with other remnants of this terrace farther up the river.

Only those streams which rise in the glaciated area have such terraces. The contrast between the Monongahela and the Alleghany in this respect is very marked. The Alleghany River throughout its course was gorged with this glacial gravel, but the Monongahela River neither had the gravel within reach nor the floods of water coming from the melting ice to distribute it if it had been within reach, therefore the gravel terraces are absent.