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CHAPTER II
GEOLOGY OF ERIE COUNTY
Volume 2 of the Geological Survey of Ohio describes Erie County as
follows:
The most interesting features in the geology of Erie County are the
splendid series of glacial markings inscribed on the corniferous limestone
in and about Sandusky City, the lake ridges which traverse the
county from east to Avest, and the remarkable petrifying fountains, knoAvn
as the Castalia Springs. In its topography, Erie County is Avithout any
strongly marked features. The surface, to the eye, seems nearly level;
while, in fact, it forms a gentle slope from the south line of the county,
where it has an elevation of 150 feet above the lake to the lake level.
This monotony of surface has been produced by the planing action of the
great glacier that excavated the basin of Lake Erie; not only that basin
Avhich IIOAV holds the water, but the greater one of which the'southern
boundary is the water shed betAveen the lake and the Ohio. Eric County,
therefore, lies near the bottom of this greater basin, and the great ice
mass filled it, moving from the northeast to the southwest, ground doAvn
the underlying rocks to a nearly uniform surface. The outines of the
lake shore have been apparently determined by the same great cause.
The general bearing of the south shore of Lake Erie is essentially the
same from near Buffalo to the mouth of the Huron River. There the coast
line forms a large angle AA'ith its former course, and stretches, with only
local variations, directly from Huron to the mouth of the Maumee. By a
glance at the map, liOAA'cver, it will be seen that the west end of Lake
Erie is blocked up with islands, and that a series of these islands stretches
northward from Sandusky and forms a barrier which must have offered
serious opposition to the westward movement of the glacier. The effect of
this ridge thrown across the lake basin and struck obliquely by the moving
mass of ice, was to deflect that slightly to the south; and to cause it
to cut the deep notch in the lake shore at the mouth of the Huron. The
excavation of this point was also facilitated by the comparative softness
of the Huron shale which underlies this portion of the county.
The drift deposits which overlie the glaciated surface in most parts
of the state have been removed from the greater part of the county. The
boAA'lder clay is, hoAvever, found covering the rock surface in the southern
part of the county. This is, as usual, a blue, or Avhere exposed and its
iron oxidized, reddish-yelloAV, unstratified clay, thickly set with angular
fragments of shale taken from the lake basin. "With these are more or
feAA'er, generally small, boAvlders, usuallv ground and striated, derived from
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