Page images
PDF
EPUB

FIGURE

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

PAGE

95

95

96

97

97 98

99

[merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small]

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

[ocr errors]

112

[merged small][merged small][ocr errors][merged small][merged small]

Section across the Northern Limestone Alps (E. Fraas)

113

47. Section across the Diablerets (Renevier)

113

48. Section across Dent de Morcles (Renevier)

114

Wallenstadt (E. Fraas, after A. Heim)

49. Inversion and Overthrust in the Mountains South of the Lake of

50. Symmetrical Flexures of the Jura Mountains

[ocr errors][merged small][ocr errors][merged small]

51.

Section across Western part of the Jura Mountains (P. Choffat)

116

[merged small][ocr errors]

53. Section across part of the Middle Carpathians (Vacek)

Section across part of the Sandstone-zone of the Middle Carpathians
(Vacek)

116

117

54. Section across the Appalachian Ridges of Pennsylvania (H. D. Rogers)

[merged small][ocr errors][ocr errors]

55. Unsymmetrical Folds, giving rise to Escarpments and Ridges
56. Structure of the Ardennes (after Cornet and Briart).
57. Diagrammatic Section across a Plateau of Erosion

[merged small][merged small][ocr errors][merged small]

58. Section across portion of Southern Uplands, showing Old Red Sandstone resting upon Plain of Erosion

[merged small][ocr errors]

59. Section from Glen Lyon to Carn Chois (Geol. Survey)

60. Section of Normal Fault.

146

153

61.

62.

Normal Fault, with High Ground on Downthrow Side
Normal Fault, with High Ground on Upcast Side

155

156

63. Faults in Queantoweep Valley, Grand Cañon District (Dutton)
64. Ranges of the Great Basin (Hinman, after Gilbert: length of section,
120 miles).

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)

[blocks in formation]

FIGURE

67. Section of Coal-measures near Cambusnethan, Lanarkshire, on a true scale.

68. Section on a true scale across "Tynedale Fault," Newcastle Coal-field 69. Section across Great Fault bounding the Highlands near Birnam, Perthshire.

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.

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)

75.

76. Section of Highly Denuded Volcano, Minto Hill, Roxburgshire
77. Diagrammatic Section across the Valley of the Tay, near Dundee
78. View of Mesa Verde and the Sierra el Late, Colorado (Hayden's Re-
port for 1875)

[ocr errors]

PAGE

166

168

169

170

170

[ocr errors][merged small]

176

177

188

189

190

[ocr errors][merged small]

79.

Wind Erosion: Table-Mountains, etc., of the Sahara (Mission de
Chadamés).

254

80.

Wind Erosion: Harder Beds amongst inclined Cretaceous Strata,
Libyan Desert (J. Walther).

254

81.

Wind Erosion: Stages in the Erosion and Reduction of a Table-
mountain (J. Walther)

[ocr errors][ocr errors][merged small]

82. Manganese Concretions weathered out of Sandstone, Arabah Mountains, Sinai Peninsula (J. Walther).

[ocr errors][merged small][merged small][merged small][merged small][merged small]

85. Longitudinal Sections of Lake-basins on a true scale

86. Sea-cliff cut in Horizontal Strata

87. Sea-cliff cut in Strata dipping Inland

[ocr errors]

259

[ocr errors]
[ocr errors]

259

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors]

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.

WHEN 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 sur face. 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.

« PreviousContinue »