xii FIGURE LIST OF ILLUSTRATIONS 31. Reversed Fault 32. Single Thrust-plane 33. Section across Coal-basin of Mons (M. Bertrand) 34. Section from Quinaig to Head of Glenbeg (Geol. Survey) 35. Synclinal Double-fold 36. Anticlinal Double-fold 37. Diagram of Mountain Flexures 39. Synclinal Valley shifting toward Anticlinal Axis PAGE 95 95 96 97 97 98 99 106 42. Section across the Schortenkopf, Bavarian Alps (E. Fraas) Section across the Kaisergebirge, Eastern Alps (E. Fraas) Section across the Val d'Uina (Gümbel) III 112 . 112 46. Section across the Northern Limestone Alps (E. Fraas) 113 47. Section across the Diablerets (Renevier). 113 114 53. 48. Section across Dent de Morcles (Renevier) 49. Inversion and Overthrust in the Mountains South of the Lake of Wallenstadt (E. Fraas, after A. Heim) 50. Symmetrical Flexures of the Jura Mountains 51. Section across Western part of the Jura Mountains (P. Choffat) 52. Section across part of the Sandstone-zone of the Middle Carpathians Section across part of the Middle Carpathians (Vacek) 54. Section across the Appalachian Ridges of Pennsylvania (H. D. Rogers) 55. Unsymmetrical Folds, giving rise to Escarpments and Ridges 58. Section across portion of Southern Uplands, showing Old Red Sandstone resting upon Plain of Erosion 136 59. Section from Glen Lyon to Carn Chois (Geol. Survey) 60. Section of Normal Fault. 61. Normal Fault, with High Ground on Downthrow Side 65. Section from the Mediterranean across the Mountains of Palestine to the Mountains of Moab (after M. Blanckenhorn). 66. Section across the Vosges and the Black Forest (after Penck) FIGURE 67. Section of Coal-measures near Cambusnethan, Lanarkshire, on a true scale PAGE 166 68. Section on a true scale across 64 Tynedale Fault," Newcastle Coal-field 168 69. Section across Great Fault bounding the Highlands near Birnam, 70. Section across Great Fault bounding the Southern Uplands 71. Diagram Section across Horstgebirge 72. 73. Mountain of Granite Plain of Granite overlooked by Mountains of Schists, etc. . 177 188. . 189 74. Diagrammatic Section of a Laccolith showing Dome-shaped Elevation of Surface above the Intrusive Rock (after G. K. Gilbert) View of Necks-Cores of old Volcanoes (Powell) 76. Section of Highly Denuded Volcano, Minto Hill, Roxburgshire Wind Erosion: Table-Mountains, etc., of the Sahara (Mission de Wind Erosion: Harder Beds amongst inclined Cretaceous Strata, Wind Erosion: Stages in the Erosion and Reduction of a Table- 82. Manganese Concretions weathered out of Sandstone, Arabah Mountains, Sinai Peninsula (J. Walther). 83. Formation of Sand-dunes 85. Longitudinal Sections of Lake-basins on a true scale 87. Sea-cliff cut in Strata dipping Inland 88. Sea-cliff cut in Strata dipping Seaward 89. Sea-cliff cut in Beds dipping Seaward 256 259 259 293 319 320 320 323 FULL-PAGE PLATES Plate I. Joints in Granite, Glen Eunach, Cairngorm (from a photograph by W. E. Carnegie Dickson) Plate II. Weathering of Joints in Granite, Cairngorm Mountains (from a photograph by W. E. Carnegie Dickson) to face 200 to face 202 EARTH SCULPTURE CHAPTER I INTRODUCTORY EARLY VIEWS AS TO ORIGIN OF SURFACE-FEATURES-ROCKS AND ROCK-STRUCTURES-ARCHITECTURE OF THE EARTH'S CRUST -GENERAL EVIDENCE OF ROCK-REMOVAL. HEN geologists began to inquire into the origin of surface-features, they were at first led to believe that the more striking and prominent of these had come into existence under the operation of forces which had long ago ceased to affect the earth's crust to any marked extent. It is not, hard to understand how this conception arose. The earlier observers could not fail to be impressed by the evidence of former crustal disturbances which almost everywhere. stared them in the face. Here they saw mountains built up of strangely fractured, contorted, and jumbled rock-masses; there, again, they encountered the relics of vast volcanic eruptions in regions now practically free from earth-throes of any kind. In one place. ancient land-surfaces were seen intercalated at inter vals among great successions of marine strata; in other places, limestones, evidently of oceanic origin, were found entering into the framework of lofty mountains far removed from any sea. It was these and similar striking contrasts between the present and the past which doubtless induced the belief that the earth's crust, after having passed through many revolutions more or less catastrophic in character, had at last become approximately stable-the occasional earthquakes and volcanic disturbances of recent times being looked upon as only the final manifestations of those forces which in earlier ages had been mainly instrumental in producing the varied configuration of the land. Mountains and valleys belonged to earth's Sturm und Drang period. That wild time had passed away, and now old age, with its lethargy and repose, had supervened. The tumultuous accumulations of stony clay, blocks and boulders, gravel and sand that overspread extensive areas in temperate latitudes were believed to be the relics of the last great catastrophe which had affected the earth's surface. Some notable disturbance of the crust, it was thought, had caused the waters of northern seas to rush in devastating waves across the land. When these diluvial waters finally retired, then the modern era began an era characterised by the more equable operation of nature's forces. But with increased knowledge these views gradually became modified. Eventually, it was recognised that no hard-and-fast line separates past and present. |