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Frontispiece Midway Geyser Basin II
Plate 1. Geologic map of Yellowstone National Park 36
Figure 1. Geographic map of Yellowstone National Park 2
2. Index map showing photograph localities 3
3. Skyline of the Gallatin Range in northwestern Yellowstone
National Park 6
4. View north along the Yellowstone River and Hayden Valley toward
the Washburn Range 6
5. The rocks of Yellowstone National Park 8
6. The geologic time scale 10
7. View downstream along the Lamar River and closeup view of
Precambrian gneiss 12
8. Positions of seaways and landmasses during the middle part of
Permian time 14
9. Crowfoot Ridge in the southern Gallatin Range 15
10. Mount Everts 16
11. The faunal succession in sedimentary rocks 17
12. Beds of limestone along Pebble Creek and closeup views of
outcrop and fossils 18
13. Common kinds of geologic structures produced by deformation of
the earth’s crust 20
14. Geologic structures in Yellowstone National Park 22
15. Intrusive and extrusive igneous rock bodies 24
16. The Absaroka volcanoes and their rocks 25
17. Massive beds of volcanic breccia of the Absaroka volcanic
rocks and closeup view of outcrop 26
18. Massive layered breccias of the Absaroka volcanic rocks at
Barronette Peak 28
19. Giant petrified tree trunks in Yellowstone’s fossil forest 29
20. Closeup view of a specimen of intrusive igneous rock 30
21. Bunsen Peak, a body of intrusive igneous rock 31
22. Outline of the Yellowstone caldera 35
23. Various stages in the development of the Yellowstone caldera 40
24. Extent of the rhyolite welded tuffs that once covered
Yellowstone National Park 42
25. The Yellowstone Tuff at Golden Gate and closeup views of tuff
specimens 43
26. Cross section through the Mount Washburn-Canyon area, showing
relationships along north edge of the Yellowstone caldera 44
27. View southeast across Yellowstone Lake toward the Absaroka
Range 45
28. Radar image of lava flows in southwestern Yellowstone National
Park 46
29. Obsidian Cliff 47
30. Thick rhyolite lava flow along Firehole River and closeup view
of specimen 48
31. Brecciated lava flows 49
32. Outcrop and closeup view of glassy rhyolite lava 50
33. Basalt flows at Tower and closeup views of outcrop and
specimen 52
34. Giant glacial boulder of Precambrian gneiss at Inspiration
Point 54
35. Glacial terrain along the Northeast Entrance Road 56
36. Typical profiles of canyons cut by stream erosion and
glaciation 57
37. Aerial oblique view of Electric Peak 58
38. Extent of ice in Yellowstone National Park during the maximum
spreading of the Pinedale glaciers 60
39. Beds of sand, silt, and clay deposited in a glacially dammed
lake in Hayden Valley 61
40. Waterfalls in Yellowstone National Park 62
41. Grand Canyon and Lower Falls of the Yellowstone River 65
42. Various stages in the development of the Grand Canyon of the
Yellowstone 66
43. Common kinds of thermal features in Yellowstone National Park 70
44. Norris Geyser Basin, showing solid floor of hot spring
deposits 72
45. Diagram of a thermal system 72
46. Infrared image of a portion of Upper Geyser Basin 73
47. Mound of geyserite (sinter) at Castle Geyser 75
48. Terraces of travertine at Opal Springs and closeup of specimen 76
49. Algal-colored terraces lining the west bank of the Firehole
River 78
50. A geyser in action 80
51. Rock rubble surrounding Seismic Geyser in Upper Geyser Basin 83
52. Old Faithful in full eruption 84
53. Mud volcano near Pocket Basin in Lower Geyser Basin 86
54. Reactivation of a fault during the Hebgen Lake earthquake of
August 17, 1959 88