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Frontispiece. Half Dome at sunset

Plate	1. Geologic map of Yosemite National Park and vicinity	II
	2. Geologic map of the Yosemite Valley area	66

Figure	1. Yosemite National Park area	1
	2. The Sierra Nevada, an asymmetric mountain range	2
	3. Summit of Mount Hoffmann, with Charles F. Hoffmann at the transit	3
	4. Views from Mount Hoffmann	4
	5. Panorama from Mount Hoffmann	6
	6. Physiographic diagram of Yosemite National Park	7
	7. Geologic time scale	9
	8. Hornblende and biotite crystals	10
	9. Plutonic-rock classification	12
	10. El Capitan Granite	13
	11. Varieties of granodiorite	14
	12. Diorite	14
	13. Dike of aplite crosscutting granodiorite	15
	14. Porphyritic texture in the Cathedral Peak Granodiorite	15
	15. Aligned dark inclusions in granodiorite	16
	16. Schlieren, layered concentrations of dark minerals	16
	17. Features that determine the relative ages of plutonic rocks	17
	18. Bird’s-eye view of Yosemite Valley	18
	19. Diorite dikes on the face of El Capitan	19
	20. Evolution of the Tuolumne Intrusive Suite	20
	21. Johnson Granite Porphyry	21
	22. Final stages in the evolution of the Tuolumne Intrusive Suite	21
	23. Contorted chert beds along the Merced River	22
	24. Metamorphic rocks with relict sedimentary bedding	23
	25. Interior of the Earth	24
	26. Major plates of the world today	25
	27. Three principle kinds of plate motion	25
	28. Oceanic plate subducted beneath continental plate	27
	29. Uplift and tilt of the Sierran block	28
	30. Ancient channel of the Tuolumne River	29
	31. Volcanic mudflow deposit	29
	32. Columnar joints in basalt at the “Little Devils Postpile”	29
	33. Regional joints shown on aerial photograph	30
	34. Inclined joints determine the slope of Three Brothers	31
	35. Staircase Falls follow inclined joints	31
	36. Rectangular blocks formed in the El Capitan Granite	32
	37. The Rockslides and El Capitan	32
	38. Bold exposure of the Half Dome Grandiorite beneath Glacier Point	33
	39. Progressive rounding of massive granite by exfoliation	34
	40. Sheet joints follow topographic surfaces	34
	41. Undulating surface below Clouds Rest	35
	42. Royal Arches, a gigantic expression of sheet jointing	35
	43. Weathering of joint blocks and formation of corestones	36
	44. Spheroidal weathering around corestones	36
	45. Weather pans formed on the summit of North Dome	37
	46. Resistant potassium feldspar phenocrysts	37
	47. Knobs of resistant diorite protrude from weathered rock surface	38
	48. Natural bridge formed from resistant aplite	38
	49. Rockfall that blocked the El Portal Road	38
	50. Deeply incised canyon of the Merced River	39
	51. Uplift and stream incision over time	39
	52. Maclure Glacier, showing annual layers of ice accumulation	40
	53. Valley glacier, showing accumulation and wastage areas	40
	54. Roche moutonnee, showing the influence of jointing on its development	41
	55. Imprints on the rock left by passing debris-laden ice	41
	56. Mountain crest, showing glacial sculpture	42
	57. Jagged unglaciated spires of Unicorn Peak	43
	58. Valley modification by glacial erosion	42
	59. Bridalveil Fall, issuing from a hanging valley	43
	60. Glacial till, an unsorted mixture of debris	44
	61. Glacial erratic left behind as the ice melted	44
	62. Moraines formed by valley glacier	45
	63. Moraines in Lee Vining Canyon	45
	64. Tioga moraine with sharp crest and abundant boulders	46
	65. Tahoe moraine with subdued crest and scattered boulders	46
	66. Perched erratic from pre-Tahoe glaciation	47
	67. Tioga icefield and valley glaciers	47
	68. U-shaped glaciated valley	48
	69. Glacial polish high on Fairview Dome	49
	70. Pothole Dome, a large roche moutonnee	49
	71. Potholes angling up the side of Pothole Dome	49
	72. Subglacial water polish on Pothole Dome	49
	73. Kettles, small lake-filled depressions	50
	74. Glacial moraines in Yosemite Valley	51
	75. Glaciers come and go in the Yosemite Valley area	51
	76. Pre-Tahoe glaciation, its extent in the Yosemite Valley area	52
	77. Dana Plateau, unglaciated remnant of an ancient land surface	53
	78. Boulder-strewn upland surface on Dana Plateau	53
	79. West shoulder of Mount Hoffmann	54
	80. Lyell and Maclure Glaciers, 1972	55
	81. Lyell and Maclure Glaciers, 1883	55
	82. Dana Glacier, 1975	56
	83. Dana Glacier, 1908	56
	84. Avalanche chutes and talus cones in Lee Vining Canyon	57
	85. The Slide on Slide Mountain	57