Bulletin - New York State Museum . le ContoTo? iiiteival 20 feet. DatiifTv is irve^vn, sea, ler^el. 2 Mies Glacialterraces. Frontalmoraine. ANCIENT WATER LEVELS OP CHAMPLAIN-HUDSON VALLEYS 113 the terrace building by gravel-bearing streams. This evidenceis stronger when it is noted that both rock terraces and glacialterraces are at this point in the river somewhat higher than atPeekskill. The elevation of the glacial terraces at Peekskill isfrom 100 to 120 feet; in the vicinity of West Point it is from160 to 180 feet. Unless there has been a differential postglacialuplift of the axis of the Hi
Bulletin - New York State Museum . le ContoTo? iiiteival 20 feet. DatiifTv is irve^vn, sea, ler^el. 2 Mies Glacialterraces. Frontalmoraine. ANCIENT WATER LEVELS OP CHAMPLAIN-HUDSON VALLEYS 113 the terrace building by gravel-bearing streams. This evidenceis stronger when it is noted that both rock terraces and glacialterraces are at this point in the river somewhat higher than atPeekskill. The elevation of the glacial terraces at Peekskill isfrom 100 to 120 feet; in the vicinity of West Point it is from160 to 180 feet. Unless there has been a differential postglacialuplift of the axis of the Highlands, this difference of level ofterraces at points about 9 miles apart, appears too great to beexplained by the normal tilting of the continent on the supposi-tion that the deposits were originally made at the same waterlevel. If made, however, in ice-confined waters, their differenceof level is expectable. In the view of the terraces at West Point and Cold Springhaving been laid down marginal to ice filling the channel in the. IFig-. 11 Cross-section of the Hudson valley at the West Point stage. A, West Point ter-race near cemetery; B, Constitution island; C, terrace south of Cold Spring-; D, CrowsNest mountain; P, ice at stage of the 400 foot morauie; G, ice at West Point terrace stage manner of glaciers in the fiords of Norway, the lack of drift onConstitution island above referred to is at once explained,since it must have been at the time covered with ice, the cross-section of the gorge then being that shown in the annexed figure. At Cold Spring on the south, facing Foundry cove, is a narrowterrace, rising about 40 feet above sea level. Partial summary of preceding chapters. The front of the icesheet retreating northward from the terminal moraine and upthe Hudson valley halted temporarily at Tappan. The extensionof the ice east and west of this locality is as yet imperfectlyknown. It certainly must have formed a broad sheet, rising onthe north, over Little and High Tor
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectscience, bookyear1887
