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Geological Survey Professional Paper 160
Geologic History of the Yosemite Valley |
CONTENTS
Geographic sketch of the Yosemite region and the Sierra Nevada
Location and character of the Yosemite Valley
Other yosemites
The Sierra Nevada
General character and dimensions
Relations to adjoining lowlands
Climatic conditions and life zones
The Yosemite region
General configuration
Hanging valleys
Stairlike steps in canyon floors
The High Sierra
General character
Merced Basin
Tenaya Basin
Tuolumne Basin
The Yosemite Valley in detail
Peculiar modeling of valley
Cliffs and rock monuments
Waterfalls
Comparison with waterfalls in other parts of the world
Summary
Early history of the Yosemite Valley
Antiquity of the Sierra Nevada and the Yosemite Valley
The Sierra block
General character and outlines
Internal structure
The rise of the Sierra Nevada
Sources of information
History of uplifts
Rearrangement of drainage system and origin of the Merced River
The cutting of the Merced Canyon
Stream-cut origin of the canyon
Evidences of three stages of cutting
The story of the cutting
Explanation of hanging valleys
Previous hypotheses
Hanging side valleys of the lower Merced Canyon
Correlation with hanging valleys of the Yosemite region
Significance of higher hanging valleys
Preservation of the Yosemite upland on massive granite
The half-yosemite at Wawona
A third set of hanging valleys
Preglacial profile of the Yosemite Valley
Interpretation of older profiles
Evolution of the Yosemite Valley in preglacial time
Landscape of broad-valley stage
Landscape of mountain-valley stage
Landscape of canyon stage
Glacial history of the Yosemite Valley
Glaciation of the Sierra Nevada
Nature of ice mantle
Distribution of ice on Sierra-Cascade chain
Origin and growth of ancient Sierra glaciers
Extent reached by ancient Sierra glaciers
Evidences of glacial action in the Yosemite region
Kinds of evidence studied
Moraines in the Yosemite Valley
Moraines in the Little Yosemite Valley
Moraines in the Tenaya Basin
Evidences of an earlier ice invasion
On the sides of the Little Yosemite Valley
In the vicinity of Glacier Point
Features at Glacier Point often mistaken for evidences of glaciation
On the south side of the Yosemite Valley
On the north side of the Yosemite Valley
In the lower Yosemite region
Difference in age between older and younger moraines
Testimony of younger glaciated rock surfaces
Testimony of older glaciated rock surfaces
Indications of a still earlier ice invasion
Ancient glaciers of the Yosemite region
Explanation of map of ancient glaciers
Glaciers of the Wisconsin stage
Yosemite Glacier
Merced Glacier
Tenaya Glacier
Snow Creek Glacier
Hoffmann Glacier
Glaciers of the Illilouette Basin
Glaciers of Bridalveil Basin
Lowest level of glacier generation
Glaciers of earlier stages
Great extent and thickness
Upper limit of glaciation in the High Sierra
Merced Glacier
Illilouette Ice Field
Bridalveil Ice Field
Tenaya Glacier
Hoffmann Glacier
Cascade Glacier
Yosemite Glacier
Transformation of the Yosemite Valley by the ice
Kernel of the Yosemite problem
Deepening effected by the Yosemite Glacier
Widening effected by the Yosemite Glacier
Muir's explanation
How do glaciers excavate?
Selective quarrying
The key to the secret of the Yosemite's origin
Configuration of the Yosemite Valley explained
Origin of glacial stairways
Application to the Yosemite Valley
Development of the Little Yosemite Valley
Development of Tenaya Canyon
Summary of changes produced by the glaciers
Postglacial history of the Yosemite region
Filling of the glacial lakes
Filling of Lake Yosemite
Filling of lake in the Little Yosemite Valley
Significance of Lost Lake
Survival of Emerald Pool
Filling of lakes in Tenaya Canyon
Production of rock waste in the Yosemite Valley
Unequal distribution of rock waste
Modes of production
Torrent fans and torrent channels
Evolution of cliff sculpture
Relation of form to structure
Influence of zones of fracturing
Forms carved in massive rock
Appendix.The granitic rocks of the Yosemite region, by F. C. Calkins
Introduction
General character of the rocks
Description of the rocks
El Capitan granite
Taft granite
Bridalveil granite
Leaning Tower quartz monzonite
Pohono granodiorite
Hornblende gabbro and hornblendic diorite
Granitic rocks of lower Yosemite region
Sentinel granodiorite
Half Dome quartz monzonite
Cathedral Peak granite
Johnson granite porphyry
Mount Clark granite
Porphyritic rocks of Clark Range
Aplite and pegmatite
Index (omitted from the online edition)
ILLUSTRATIONS
PLATE
1. Relief map of California2. Topographic map of Yosemite National Park (omitted from the online edition)
3. Yosemite Valley from Wawona Road
4. A, Little Yosemite Valley; B, Tehipite Valley
5. A, Kings River Canyon; B, Retch Hetchy Valley; C, East front of Sierra Nevada
6. A, Characteristic storm-bent tree at timber line; B, Giant sequoias in Mariposa grove
7. Topographic map of Yosemite Valley (omitted from the online edition)
8. A, Tenaya Canyon from Glacier Point; B, View across Yosemite Valley from Ribbon Fall
9. A, View northward over Yosemite upland from Horse Ridge; B, Hanging valley of Yosemite Creek and Yosemite Falls, from Glacier Point
10. The giant stairway from Glacier Point
11. A, The High Sierra from El Capitan; B, Little Yosemite and Clark Range from Half Dome
12. A, Cathedral Peak; B, Merced Lake
13. A, Tuolumne Meadows; B, Head of upper Merced Basin
14. Mount Lyell and Lyell Glacier
15. Bird's eye view of Yosemite Valley and the High Sierra
16. A, Lower end of Yosemite Valley and head of Merced Gorge; B, Head of Yosemite Valley from Columbia Rock
17. El Capitan from the east
18. Cathedral Rocks and Cathedral Spires
19. A, Sentinel Rock; B, The Three Brothers
20. A, North Dome from Merced River near Happy Isles; B, Silhouette profile of cliff at Glacier Point
21. A, Sentinel Dome; B, The Royal Arches and the Washington Column surmounted by North Dome
22. Yosemite Falls from the Merced River
23. A, Bridalveil Fall; B, The Cascades; C, Lower Yosemite Fall
24. Vernal Fall
25. Nevada Fall and Liberty Cap
26. A, View down lower Merced Canyon from El Capitan; B, Upturned beds of slate and schist in lower Merced Canyon; C, Contorted layers of chert exposed in bed of Merced River
27. A, Longitudinal profile of Yosemite Valley; B, Longitudinal profile of Merced Canyon and Yosemite Valley
28. A, Empty cirque on Kuna Crest; B, Dana Glacier
29. Map of glacial and postglacial deposits (omitted from the online edition)
30. A, Crest of morainal embankment on the side of Moraine Dome; B, One of the lateral moraines on north side of Little Yosemite Valley
31. A, View across Little Yosemite Valley from a point near Helen Lake; B, The great morainal embankment from top of Moraine Dome
32. A, Sandy flat in Illilouette Valley and Starr King group; B, Lateral moraines of Merced Glacier on south side of Little Yosemite Valley
33. A, Weather pit at Glacier Point; B, Typical perched boulder of an earlier glaciation; C, Weather pits in slab on North Dame
34. A, Old moraine near Wawona Road; B, Typical pothole of subglacial origin at lower end of Tuolumne Meadows
35. A, Glacial grooves on border of lake in Cathedral Pass; B, Glacier polish on floor of massive granite
36. Glaciated floor and side of upper Merced Canyon
37. A, Wall of aplite on Moraine Dome; B, Large erratic boulder on Moraine Dome
38. A, Glacial boulder perched on 5-foot pedestal; B, Erratic boulder at base of Sentinel Dome
39. Map of ancient glaciers of Yosemite region
40. A, Echo Peaks and the Cockscomb; B, The great ??? façade of Clouds Rest from Mount Watkins
41. A, Crest of Sierra Nevada and head of Tuolumne Basin; B, Well-jointed granite in the High Sierra
42. A, Moraine composed of angular blocks; B, Joint blocks loosened by frost
43. A, Turtleback Dome and Merced Gorge below Yosemite Valley; B, Glaciated rock mass under Glacier Point
44. A, Rear view of Liberty Cap and Mount Broderick; B, Front view of Liberty Cap and Mount Broderick
45. A, Cascade Cliffs, in Little Yosemite Valley; B, Sugar Loaf and Bunnell Point from Moraine Dome
46. A, Upper part of Tenaya Canyon from upper Quarter Dome; B, The rock facade of Clouds Rest from upper Quarter Dome
47. A, Mirror Lake; B, Agassiz Column
48. A, Arched exfoliation shell; B, Brink of precipice of upper Yosemite Fall; C, Exfoliating granite on lower Quarter Dome
49. Northeast side of Half Dome
50. A, Back of Half Dome; B, Front of Half Dome
51. Geologic map of Yosemite region
52. A, Half Dome quartz monzonite; B, Cathedral Peak granite, polished by the ancient glaciers
FIGURE
2. Idealized cross section of Sierra block (omitted from the online edition)
3. Block diagram illustrating parallel mountain ranges carved from strongly folded strata
4. Cross sections illustrating successive stages in the cutting of Merced Canyon
5. Longitudinal profile of Saxon Gulch
6. Longitudinal profile of hanging valley of Feliciana Creek
7. Longitudinal profiles of hanging valley of Fireplace Creek and of ravine on opposite side of Yosemite Valley (omitted from the online edition)
8. Longitudinal profile of hanging valley of Indian Creek
9. Longitudinal profile of hanging valley of Yosemite Creek
10. Longitudinal profile of hanging valley of Bridalveil Creek
11. Longitudinal profile of hanging valley of Chilnualna Creek
12. Longitudinal profiles of hanging gulch of Bridalveil Creek and of hanging upland valley of Ribbon Creek
13. Bird's-eye view of Yosemite Valley in broad-valley stage
14. Bird's-eye view of Yosemite Valley in mountain-valley stage
15. Bird's-eye view of Yosemite Valley in canyon stage
16. Bird's-eye view of Yosemite Valley immediately after the ice age
17. Idealized sketch of a glacier leaving successive moraine loops as it melts back
18. Section across moraine dam at El Capitan Bridge
19. Sketch showing in section lateral moraines on north side of Little Yosemite Valley
20. Section across lateral moraines on south side of Little Yosemite Valley
21. Section across parts of Moraine Dome
22. Longitudinal profiles of Yosemite and Merced Glaciers in the El Portal and Wisconsin stages of glaciation
23. Section across Tenaya Canyon and Little Yosemite showing highest levels reached by Tenaya and Merced Glaciers
24. Cross profile from Eagle Peak to Sentinel Rock
25. Cross profile from North Dome to Glacier Point
26. Cross profile below Bridalveil Meadow
27. Cross profile from El Capitan to the Cathedral Rocks
28. Cross profile at head of Merced Gorge
29. Cross profile at mouth of Little Yosemite Valley (omitted from the online edition)
30. Cross profile at middle of Little Yosemite Valley
31. Diagram illustrating the quarrying of joint blocks by a glacier
32. Longitudinal section of a canyon illustrating the development of a glacial stairway by the recession of successive cross cliffs
33. Longitudinal section of a typical roche moutonnee
34. Longitudinal section of a canyon illustrating the development of a glacial stairway by selective quarrying
35. Longitudinal section of Yosemite Valley
36. Section across Little Yosemite Valley
37. Section across Merced Gorge above Little Yosemite Valley
38. Diagram showing how by progressive exfoliation the angularities of a rock mass are replaced by smooth curves
UNITED STATES DEPARTMENT OF THE INTERIOR
RAY LYMAN WILBUR, Secretary
GEOLOGICAL SURVEY
George Otis Smith, Director
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Last Updated: 28-Nov-2006