Niagara Gorge and Saint Davids Channel
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BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA V o l. 9, pp. 101-110 J a n u a r y 25, 1898 NIAGARA GORGE AND SAINT DAVIDS CHANNEL BY WARREN UPHAM (Read, before the Society December 80, 1897) CONTENTS Page Introduction ................................ ........................... ....................................................... 101 Niagara gorge............................................. ...................................................................... 102 Physical features in general................................................................................... 102 From Lewiston to the Whirlpool........................................................................... 103 The Whirlpool.................................. ................... .................................................... 104 The Whirlpool rapids............................................................................................... 104 From the rapids to the fells................................................................................. 104 Saint Davids channel..................................................................................................... 104 From Saint Davids to the Whirlpool................................................................. 104 Probable preglacial extent above the Whirlpool............................................... 105 Effect on the recession of the falls....................................................................... 106 Effect of the Laurentian glacial lakes on the Niagara Gorge erosion.................. 107 Glacial lakes above Niagara river......................................................................... 107 Glacial lakes below Niagara river......................................................................... 108 Epeirogenic uplifting contemporaneous with the glacial lakes....................;.... 108 Epeirogenic movement continued to the present tim e............................................ 109 Duration of Niagara falls and the Postglacial period............................................. 109 I ntroduction Having recently again examined the Niagara falls and gorge with especial reference to the Older channel of Saint Davids, I believe that a most important element in the history of the gorge erosion has been over looked by some observers, and that by others its evidences have been misunderstood. This paper shows that the small preglacial stream which eroded the Saint Davids and Whirlpool channel, having a great depth beneath the river in the Whirlpool, must have flowed for a considerable distance, before reaching'that depth, in a gradually widening and deepen ing ravine, coinciding with the present gorge along the Whirlpool rapids. Because the Niagara river found there a drift-filled narrow ravine, which it cut to the preserit size of the gorge, its erosion took place in that part by rapids and cascades. Southward from the head of the old ravine the river has eroded its gorge by a great vertical cataract, under which the XV—B ull. Geol. Soc. Am., Vol. 9, 1897 (101) Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/9/1/101/3429678/BUL9-0101.pdf by guest on 02 October 2021 102 W. UPHAM— NIAGARA GORGE AND SAINT DAVIDS CHANNEL. masses of the Niagara limestone, rolled about by the power of the water fall, have worn the river bed to a maximum depth of nearly 200 feet be neath the water surface. The narrowness of the gorge along the Whirlpool rapids is therefore attributed to the conditions of the river erosion here indicated, rather than to decrease of the volume of the river (which several geologists have thought probable or certain) by diversion of the water of the upper lakes to flow from lake Huron eastward. Studies of the glacial lake Agassiz and of the Laurentian glacial lakes convince me that the progress of the epeirogenic uplift of the northern United States and Canada from the Champlain depression was too rapid to accord with the hypothesis of any outflow from lake Huron toward the east during the long time that would be required for the Niagara river, while thus diminished, to erode the gorge along the Whirlpool rapids. The explanations here given to account for the variation in the width of the Niagara gorge, and for its partly very rapid and partly very deep and gently flowing river, with the relation of this gorge to the Saint Davids channel and the upper continuation of that channel by a ra vine, accord mainly with Dr Julius Pohlman’s discussion of the Niagara history; but his conclusion that the age of the river and of Postglacial time has been only about 3,000 years is here regarded as probably less acceptable than a higher estimate. The present writer thinks that the Niagara gorge implies for the Postglacial period, in harmony with Pro fessor N. H. Winchell’s discussion of the recession of the falls of Saint Anthony, a duration between 5,000 and 10,000 years. Niagara Gorge p h y s i c a l f e a t u r e s i n g e n e r a l A gorge about 6 i miles long, extending southward from the Niagara limestone escarpment at Lewiston and Queenstown to the apex of the Horseshoe falls, has been eroded by the river since the withdrawal of the border of the continental ice-sheet from this district. The width of the gorge at its top varies mainly from 1,000 to 1,500 feet, but is only 650 to 800 feet for three-fourths of a mile along the upper part of the Whirl pool rapids and at the railway bridges. The depth from the brink of the gorge to the river is mainly about 300 feet, but is decreased above the rapids to about 225 feet. To this depth, however, must be added that of the river itself, making the whole depth of the gorge to the bottom of the water somewhat more than 400 feet at its northern end, at the Whirl pool, and between the railway bridges and the falls. The sides of the gorge through all their length, excepting at the Foster Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/9/1/101/3429678/BUL9-0101.pdf by guest on 02 October 2021 PHYSICAL FEATURES. 1 0 3 flats and on the north side of the Whirlpool, are nearly or quite vertical in the upper part, -which consists of the Niagara limestone, and are very steep below, where a talus is formed by the fallen debris of the limestone and of the underlying shales and the inclosed beds of limestone and sandstone. These strata are nearly horizontal, but have a slight dip southward, which, according to Spencer, amounts to about 75 feet in the whole extent of the gorge, being least (only 10 feet) in the distance of three miles between the Whirlpool and the falls. No appreciable difference in the amount of subaerial decay and change, or weathering, of the rock walls is found when we compare the older northern part of the gorge and the newer southern part. In a very long geologic period the precipitous walls would be reduced to gentle slopes and would become indented by wide tributary ravines ; but scarcely any perceptible progress toward this result has been made during the geolog ically very short period since the gorge began to be eroded. FROM LEWISTON TO THE WHIRLPOOL In this older part of the gorge, measuring 3J miles, the river descends about 31 feet, from 280 to 249 feet above the sea; and in its further course of 7 miles, to lake Ontario, it descends, at the ordinary stage of water, about 2 feet. After its narrow egress from the Whirlpool the river flows some 50 rods with its surface ruffled by the force of its current; next it is smooth for about half a m ile; thence, adjoining the broken and irreg ular northwestern side of the gorge (called Foster flats), the stream is narrowed (having a minimum width of about 300 feet) and runs a mile in foam-crested rapids; through the next mile it has a very strong cur rent, but little or no foam and broken water; and along the remaining distance of about a mile to the Niagara escarpment and Lewiston the current is less and can be stemmed by the river steamers. Owing to the formerly much lower level of the western part of lake Ontario and its gradual rise to its present height, to be explained in later pages in treating of the Laurentian glacial lakes and the Champlain and Recent epeirogenic uplift of the region, the river eroded a channel at Lewiston and northward far below its present surface, its depth of water at the mouth of the gorge being 96 feet., Its depth in the heaviest part of the rapids adjoining the Foster flats is computed by Gilbert, from the velocity and volume, to be about 35 feet, and he estimates the depth to be about 100 feet for half a mile next above these rapids to the other very short rapids at the shallower and narrowed egress from the Whirlpool. The selection of this route by the Niagara river when it was first brought into existence by the melting away of the ice-sheet here and the reduc tion of the glacial lake Warren to its successors, lakes Algonquin and Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/9/1/101/3429678/BUL9-0101.pdf by guest on 02 October 2021 104 W. UPHAM— NIAGARA GORGE AND SAINT DAVIDS CHANNEL. Iroquois, and the probable conditions of the erosion of this part of the gorge, will be considered further on in their relation to the Saint Davids channel. THE WHIRLPOOL In the huge caldron of the Whirlpool the waters of the river, coming in from the southeast, sweep around continually to the left, bearing many logs and other floating objects, while a part of the surface water on the right of the entering rapids, with a deep undertow, pours forth to the northeast, making a right angle with the course of entrance. The mini mum and maximum diameters of the pool are about 1,100 and 1,800 feet, and its depth is estimated by Gilbert to be about 150 feet. THE WHIRLPOOL RAPIDS Along a distance of one mile, from the railway bridges to the Whirl pool, the river rushes madly in most majestic rapids, having a descent of 70 feet, from 350 to 280 feet above the sea. Its width is reduced for three- fourths of a mile to about 400 feet, and its depth, according to Gilbert’s computations, is about 35 feet.