La physiographie forestière; la physiographie des États-Unis et les principes des sols en relation avec la foresterie . est illustrée à la Fig. 284, et prouve que les vallées étaient des autoroutes de mouvement moréactif de la glace. Les faits les plus importants qui pointent vers la complexité de l'origine concernent les vallées suspendues tributaires des lacs Finger. Sur les pentes abruptes des côtés de la vallée principale, une série de gorges enterrées a été trouvée. • Williams, Tarr Et Kindle, Watkins Glen-Catatonk Folio U. S. Geol. Surv. N° 169,Field éd., 1909, p. 124. 7 o PHYSIOGRAPHIE FORESTIÈRE Les gorges sont occupées par des dépôts de dérive du dernier

• Contributeur: The Reading Room / Alamy Banque D'Images
• ID de l’image: 2AXA87E
• Taille du fichier: 7,1 MB (473,3 KB Téléchargement compressé)
• Autorisations: Modèle - non | Propriété - non
• Dimensions: 2158 x 1158 px | 36,5 x 19,6 cm | 14,4 x 7,7 inches | 150dpi

Informations supplémentaires

Cette image appartient au domaine public, ce qui signifie que le droit d’auteur a expiré ou que le titulaire du droit d’auteur a renoncé à ses droits. Les frais facturés par Alamy couvrent l’accès à la copie haute résolution de l’image.

Cette image peut avoir des imperfections car il s’agit d’une image historique ou de reportage.

Forest physiography; physiography of the United States and principles of soils in relation to forestry . is clearlyshown in Fig. 284, and proves that the valleys were highways of moreactive glacial motion. The most important facts pointing to complexity of origin relate tothe hanging valleys tributary to the Finger Lakes. On the steepenedslopes of the main valley sides a series of buried gorges has been found. • Williams, Tarr, and Kindle, Watkins Glen-Catatonk Folio U. S. Geol. Surv. No. 169, field ed., 1909, p. 124. 7IO FOREST PHYSIOGRAPHY The gorges are occupied by drift deposits of the last (Wisconsin) ice inva-sion, which indicates that they were formed before that invasion.^ From the known facts it is concluded that before the glacial periodthere was a system of mature drainage with main valleys along the axesof Cayuga and Seneca lakes and with tributaries entering them atgrade. With the overspreading of the region by glacial ice there wasbegun a process of exceptional deepening in the main valleys because theyserved as lines of most rapid glacial flow. At the end of the first ice. UD EZ] B ^ [3 MB ORDOVICIAN SILURIAN DEVONIAN MISSISSIPPIAN Fig. 285. — Map of portion of New York, i, Ordovician; 2-5, Silurian; 6-13, Devonian; 14, Mississipian. invasion the valleys had been broadened and deepened, the amount ofthe deepening being about 500 feet. Lakes may have formed in theseoverdeepened valleys after the ice had been melted away. At any ratethe discordance of level between tributary and master valleys was pro-nounced and the tributaries began to cut down their valleys to the levelof the main valleys, making gorges of notable breadth and depth beforethe second glacial invasion filled them with drift, reexcavated anddeepened the main valleys, increased the discordance between tributariesand master streams, and so altered the topography in detail that thepostglacial streams do not flow everywhere in the interglacial courses.Wherever a postglacial stream enters

Recherche dans la banque de photos par tags

• bookcentury1900
• bookdecade1910
• booksubjectforestsandforestry