Erie. - Area, 770 square miles; population in 1880,74,688.
Its Straight Lake Erie shoreline, 23 miles long, is only broken by
the hook-shaped peninsula in front of the city of Erie. The present
level of the lake is 573` A.T. A bluff of sand and clay faces the
shore, lower at the Ohio line, but increasing in height eastward,
often abruptly rising 80`, 100`, and even 120` above the lake. From
the brow of the bluff back (southward) the surface slopes up gently
to the foot of an escarpment, 400` to 450` above the lake, (1000`
A.T.) The escarpment itself then rises boldly to a summit line of
1300`, towards the west, and 1500`, towards the east, back of which
lies the upland of the middle and southern townships, at an elevation
ranging from 1400` at the west to 1700` at the corner of New York.
The eastern half of the upland drains, by the head branches of French
Creek, southward; the western half sheds its waters through the two
deep ravines of Elk and Conneaut Creeks into Lake Erie. The face of
the escarpment and the 1000` terrace beneath it cast their rainfall
directly into the lake by smaller streams like Raccoon, Crooked, Trout,
Walnut, 4-Mile, 6-Mile, Elliott’s, Scott’s, 12-Mile, and 16-Mile runs.
The level of Lake Erie stood once much higher than now; for in Harbor
Creek and North East townships four terraces may be counted at 1150`,
1070`, 875`, to 795`, and 765` to 740`, the top of the sand bluff
overhanging the lake (573`A.T.) The lowest terrace, a plain a mile
wide, is covered with a lake deposit of brick-clay; the second
terrace, a broad, sloping plain, exhibits a steep escarpment of lake
beach sand, 40` high, extending for a long distance parallel
to the present shore; and at 1070` are remnants of a terrace covered
with beach sand and shingle; but the 1150` plain, 3 miles back
from the lake, is destitute of such deposits. * Glacial drifts cover
the whole county, and deeply fills all its water channel beds. The
upland formations consist of (1) Pocono sandstone and shale
(X) along the Crawford County line, on isolated divides in Wayne and
Amity townships, and a long irregular ridge from Mill village to Franklin
corners; and (2) the Oil Sand group, which spreads around
and north of the Pocono areas to the brow of the great escarpment
looking down upon the lake. This is made by the outcrop of the lowest
or 3d Oil Sand, quarried in many places for building stone, and generally
more or less dripping petroleum, but affording no assurance of containing
paying quantities of the oil in any part of the county. The dip is
everywhere extremely gentle, a careful calculation making it 22 feet
to the mile, S. 45º
W. (See Report Q4, p. 54.) The (Lower?) Chemung
rocks (325`) cropping out along the upper steeps of the escarpment
and over the broad, flat valleys of French and LeBoeuf Creeks, and
covering the southwest corner of the county, are very fossiliferous.
The next underlying Girard shales (225`), destitute of fossils
except markings supposed to be sea weeds, are exposed in the ravines
descending towards the lake, and especially in that of Elk Creek,
the sides of which resemble vast banks of gray coal-ashes; the bottom
of this formation touches the lake level at Raccoon Creek near the
Ohio State line, and gradually rises to 475` above the lake at the
New York State line. The next underlying Portage formation
of alternate layers of gray shale and thin hard sandstone, non-fossiliferous
(except fucoids), occupies the lakeshore. Petroleum trickles from
some of the sand layers, which are never more than one or two feet
thick, and represent the Warren Oil Sand Group. Collections of condensed
gas exist, which produce little explosions at the building stone quarries.
The gas and oil wells which have lighted and heated the city of Erie
vary in depth from 450` to 1200`, the average being about 600`, which
should not be far from the Bradford Oil horizon. Building stone of
excellent and various character is the only mineral wealth of Erie
county, and quarries are numerous in the Shenango
(Sub-Olean) sandstone belt of the southern townships; in the three
coarse Oil Sands; and also in the finer sandstone layers of the Portage
series, east of Erie, along the lake. (See Report Q4.)
*This, of course, implies a continental submergence;
for the highest Erie R.R. grade (at Batavia) is only 895` A.T.D--X
From: A geological hand atlas of the sixty-seven
counties of Pennsylvania :embodying the results of the field work
of the survey, from 1874 to 1884. By J. P. Lesley. (Report of
progress (Geological Survey of Pennsylvania), v. X ) Harrisburg, PA
: Board of commissioners for the second geological survey, 1885.
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