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one near Northfield, and one in Boston, the last capping the Cuyahoga Valley wall and giving rise to the picturesque scenery of the "Boston Ledges." Eight of them lie west of the Cuyahoga River in the southwestern part of the Cleveland quadrangle, but only one is of much size, and four of the eight are very small. Two occur in the Berea quadrangle. Taken together these form all that remains within the quadrangles of this sandstone platform, the original surface of the plateau. The topographic prominence that rightly belongs to them has in many places been greatly subdued by heavy banking of glacial drift against their fronts and in the lower lands between them. Some of them stand out as prominent hills, 100 feet or more above the level of the surrounding territory, flat topped and steep fronted or surrounded by low ledges. Upon many the soil is thin and poor, and they remain largely forested. Between these hills the sloping surface is gently rolling from an altitude of 1,100 or 1,200 feet down to about 900 or 1,000 feet, whence the slopes descend more steeply to the valleys of the Cuyahoga and Rocky Rivers.

This region does not suggest a plateau, but southeast of these quadrangles the plateau surface is distinct and more nearly continuous. The margin of the plateau in the Cleveland region has been dissected by stream erosion until it has been reduced to long promontories projecting northward from the main area of the plateau, and outlying patches have been wholly separated from it.

Portage escarpment.-The Portage escarpment is the irregular slope 2 to 4 miles wide that descends from an altitude of 1,200 or 1,240 feet on the northwestern edge of the Appalachian Plateaus to 700 or 800 feet at the southeastern margin of the Erie Plain. It is irregular and discontinuous because of the large valleys cut into the plateau, and it bends away from its southwesterly trend into the walls of these valleys. Its upper, southeastern limit has the intricate outline of the dissected margin of the plateau surface; its foot, bordering the plain, is much more continuous and regular. Northeast of Cleveland, in the Euclid quadrangle, the Erie Plain is abruptly terminated immediately southeast of Euclid Avenue by the foot of the Portage escarpment, at an altitude of 680 to 740 feet. In the northern third of the Cleveland quadrangle the foot of the escarpment bends southward into the east wall of the Cuyahoga Valley. West of the Cuyahoga River the southern margin of the Erie Plain or the foot of the escarpment, is not so sharply defined. Where the west wall of the valley bends westward into the escarpment, across Independence Township, it lies along Rockside Road, at an altitude of about 800 feet. Across Parma Township the margin may be regarded as bending southwestward at an altitude of either 800 or 880 feet, depending on whether the low Berea scarp (see p. 13) is included or not.

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In the south-central part of the Berea quadrangle the Portage escarpment assumes the southerly trend that carries it entirely across Ohio, Kentucky, and Tennessee. The northern and western threequarters of the quadrangle lie within the Erie Plain. The foot of the escarpment runs east of Berea, crosses the East Branch of the Rocky River near Strongsville, and runs east of the West Branch at the south line of the quadrangle. It is obscure in places but has an altitude between 800 and 900 feet.

The greater part of the Portage escarpment is made up of the long, gentle slopes of shale that descend from the Pottsville to the Berea terrace, or roughly that part of the Cleveland and Euclid quadrangles lying between 900 and 1,150 feet in altitude and of the Berea quadrangle between 800 and 1,150 feet. The general direction of the slope is northwest, but it is not sharply separated from the slopes. of the valleys crossing the escarpment. There is some dissection by narrow, shallow stream valleys, but otherwise the slope is fairly uniform, descending from 40 to 80 feet to the mile and mantled everywhere with glacial drift. Rock outcrops are found principally in the stream valleys, and by no means in all, as many streams flow for miles in channels that nowhere cut through the drift.

The outcrop of the Berea sandstone makes a minor escarpment 30 to 50 feet high, which may be called the Berea scarp and which extends across the Euclid and Cleveland quadrangles in a southwesterly direction as far as the Cuyahoga Valley, where it swings to the south as a well-defined bench along the valley wall. As such it continues to the south margin of the Cleveland quadrangle, with a steady decrease in altitude, which brings it down to the level of the river about 3 miles farther south. There is a companion terrace on the west side of the valley. West of the Cuyahoga the Berea scarp continues westward and southwestward to the Rocky River at Berea, but the Berea sandstone declines in altitude, and the scarp is an obscure gentle slope of about 50 feet in a mile. At Berea the Berea sandstone descends below the level of the Central Lowland or Erie Plain and exerts no influence on the topography of the plain from Berea 13 miles westward to Elyria, in the Oberlin quadrangle, where it is again effective.

East of the Cuyahoga River the Euclid sandstone is present 50 feet below the Berea and caps part of a well-defined slope and terrace, the first rise of the Portage escarpment above the Erie Plain. West of the Cuyahoga Valley the Euclid sandstone and its terraces are absent, except for a small elevated area between 780 and 800 feet in altitude on the southern edge of the plain, in Brooklyn Township.

East of the Cuyahoga River the Portage escarpment forms three distinct steps, the first from 100 to 150 feet above the Erie Plain, largely under the influence of the Euclid sandstone; the second 50

feet higher and half to three-quarters of a mile south, the Berea sandstone; the third about 300 feet higher, 3 miles farther south and obscurely defined at the position of the Sharon conglomerate, at the edge of the Appalachian Plateaus.

West of the Cuyahoga River the Portage escarpment is not so high as on the east and consists of a single rise steeper than that east of the river, with the obscure Berea platform at its base.

Glacial deposits so thoroughly mantle the surface and clog the old valleys of the plateau and the escarpment slope that the present topography is much less varied than that which would be disclosed by the removal of these deposits. The plateau was deeply trenched by many old valleys, and its topography was much more rugged than it is now. It was a topography of mature stream dissection, in strong contrast to the present immaturity.

Two low morainic ridges, the Cleveland and Euclid moraines, slightly diversify the smooth slopes of the plateau and plain. The most westerly place at which the Cleveland moraine is recognizable as a distinct topographic feature is near Linndale, whence it runs to Brooklyn, following a course not far south of the valley of the main trunk of Big Creek. It is 20 to 30 feet high and about three-quarters of a mile broad. It is interrupted by the Cuyahoga Valley, but it reappears at Newburg, where it shows a number of knolls of gravelly drift, and continues east to Randall, where it joins the Defiance moraine and thence continues to the edge of the Cleveland quadrangle and beyond. In this part of its course, however, it is so low and so broad that its topographic expression is very indistinct. It is not mapped between Newburg and Randall.

The Euclid moraine shows only its west end in the Euclid quadrangle, just east of Euclid, as a thin mantle of till in a gentle ridge lying along the terrace at the top of the lowest or Euclid scarp. The terrace is not capped by the Euclid sandstone at this place. The Euclid moraine is noteworthy here as marking the west end of a series of moraines that follow the lower slopes of the Portage escarpment to the east end of Lake Erie, have much to do with the present configuration of the escarpment, and exert a profound influence upon the drainage of northeastern Ohio.

Erie Plain.-A considerable part of the Erie Plain is submerged beneath the waters of Lake Erie. Out in the lake is a channel of moderate depth that is probably best regarded as cut below the level of the plain, but with this exception the entire lake is shallow, and the bottom belongs with the Erie Plain. East of the Cuyahoga that part of the plain above the lake is only 2 to 3 miles wide and reaches the foot of the escarpment at an altitude of 700 feet at Euclid and 740 feet at Cleveland. The surface has a lakeward slope of 50 to 60 feet to the mile but is very smooth, except for the abandoned lake

strands described below. The streams flow across it in shallow valleys that are deepest near the escarpment. The brook valleys are cut in the plain to depths of 10 to 40 feet, and the rivers run 40 to 100 feet below its level.

West of the Cuyahoga River the escarpment of the Euclid sandstone is absent and there is no sharp southern limit to the plain. Between the Cuyahoga and Rocky Rivers the plain may be regarded as from 4 to 5 miles broad and as rising from the lake cliffs to an altitude of about 800 feet. West of the Rocky River its breadth increases to 17 miles. Here also its slope to the lake is more gentle-approximately 20 feet to the mile. The surface is very even, except where varied by shallow brook valleys and low lake ridges.

The shore line of Lake Erie at most places is a steep or vertical wave-cut cliff from 30 to 50 feet high, broken only by the stream valleys that come down to the lake. Sand beaches are few and small. Much of the wave-cut shelf at the foot of the cliff is under water and impassable; where it is above water it is narrow. The shore line is fairly straight, and the storm waves sweep strongly against it. The cliff is composed of weak material, in places till or sand, in places shale, and the recession is moderately rapid, especially in the till or sand. In front of Cleveland, where the cliff consists of sand and lake clay, the recession was especially rapid until checked by driving piles and more recently by expensive breakwater construction. Deltas can not accumulate at the mouths of the streams. Bars form in front of the streams, but the bulk of the discharged material is carried. alongshore by the current and distributed as offshore sand bars.

On the broad expanse of the Erie Plain, west of the Rocky River, are three low ridges, locally known as North, Middle, and Butternut Ridges. These ridges are roughly parallel to one another and to the lake shore but diverge slightly westward. They are plainly shown on the topographic map of the Berea quadrangle. Their crests rise from 10 to 30 feet higher than the surface of the plain just north of them, and from the crest of each there is, in many places, a gentle back slope to the south, dropping from 3 to 5 feet. These features are beach ridges formed at higher stages of Lake Erie, as explained under "Geologic history" (pp. 98-99).

The crest of Butternut Ridge has an altitude of 760 to 780 feet across the Berea quadrangle, except where it is interrupted by the Rocky River Valley. East of Linndale it abuts against the north side of the Cleveland moraine. East of this point it is hard to trace and has no importance as a topographic feature.

Middle Ridge lies from 1 to 2 miles north of Butternut Ridge. Its crest is at about 730 feet, about 40 feet lower than that of Butternut Ridge. Its course is interrupted by the Rocky River Valley and by the great trench of the Cuyahoga Valley. It is present between the

Rocky and Cuyahoga Rivers, where Dennison Avenue follows its crest. In the eastern part of Cleveland it lies just in front of the base of the escarpment, with its summit at about 730 feet. In the Euclid quadrangle it disappears as a ridge because the base of the escarpment drops to 700 feet and the level of the ridge is therefore about 30 feet up on the steep slope of the escarpment, where a ridge could not be developed. Here, a closely related topographic feature is found in a distinct platform from 100 to 150 yards in width, cut into the face of the escarpment about 40 to 45 feet above its base, and just south of Euclid Avenue.

North Ridge is about 3 miles north of Middle Ridge at the west margin of the Berea quadrangle and only half a mile north of it at the east margin. It is the only one of the three ridges that is continuous and strong entirely across the Cleveland and Euclid quadrangles except as it is interrupted by the Rocky River and Cuyahoga Valleys. Through the western part of Cleveland Detroit Avenue follows it rather closely; on the east side Euclid Avenue continues with it to Fortieth Street. Thence to a point east of Doan Brook it lies north of Euclid Avenue. East of Doan Brook this shore line is not a ridge but a wavecut cliff, which forms the foot of the Portage escarpment and is followed very closely by Euclid Avenue to the east boundary of the Euclid quadrangle. The crest of this ridge or base of the cliff, as the case may be, is at about 680 feet-about 50 feet lower than Middle Ridge and cliff.

These beach ridges or cliffs, formed at higher stages of Lake Erie, are not the only ridges of the same type that occur within the quadrangle, but the others are too faint and too much interrupted to be notable topographic features.

Valleys. The valleys of the quadrangles are of varied topography according as they do or do not coincide in location with old preglacial valleys. There are three types of stream valleys-old valleys, new valleys, and those that are part old and part new. Of the lastmentioned type there are two subtypes-those in which the lower part of the valley is old and the upper part new, and those in which the lower part is new and the upper part old. Within these quadrangles the Cuyahoga is the only stream of the first type, but the river enters its old valley 10 miles south of this area, and all its upper course is new, so that its valley as a whole belongs to the first subtype of the third group. The Rocky River is an excellent example of the second subtype, and Tinkers Creek is another. Euclid Creek and Big Creek flow in wholly new valleys.

The Cuyahoga Valley was partly filled with sand and silt in ponded glacial waters. Some of this filling has been cleared away by the river, and to an observer looking across from the summit of either valley wall, a broad and fairly deep valley is open to view bordered on

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