Washington Department of Natural Resources Geology and Earth Resources Division Information Circular 90 Flood Basalts and Glacier Floods: Roadside Geology of Parts of Walla Walla, Franklin, and Columbia Counties, Washington Robert J. Carson and Kevin R. Pogue

Cover

Front Cover: Palouse Falls (56 m high) in the canyon of the Palouse River.
Back Cover: Route of the field trip. Stop locations are indicated by the circled numbers.

General geology of southeastern Washington

Magnetic polarity
Geologic time
Columbia River Basalt Group
Tectonic features
Quaternary sedimentation

Road log

Further reading

Acknowledgments

Road Logs

Part 1 — Walla Walla to Palouse Falls (69.0 miles)
Part 2 — Palouse Falls to Lower Monumental Dam (27.0 miles)
Part 3 — Lower Monumental Dam to Ice Harbor Dam (38.7 miles)
Part 4 — Ice Harbor Dam to Wallula Gap (26.7 miles)
Part 5 — Wallula Gap to Walla Walla (42.0 miles)

References cited

Figure 1. Physiographic map of the Columbia Plateau

Figure 2. Map showing distribution of the Columbia River Basalt Group

Figure 3. Stratigraphic section for the central and southeastern Columbia Plateau

Figure 4. General cross section of the field trip area

Figure 5. Map showing late Pleistocene glaciers, lakes, and floods in the northwestern United States

Figure 6. Map showing the Channeled Scabland of Washington

Figure 7. Map showing the route of the field trip

Figure 8. Photograph of the Palouse Hills between Walla Walla and Starbuck

Figure 9. Photograph of loess north of Dixie

Figure 10. Photograph of stripcropping south of Waitsburg

Figure 11. Photograph of a quarry east of Waitsburg (Stop 1)

Figure 12. Diagrammatic cross section of Steptoe Butte

Figure 13. Photograph of the contact between the Grande Ronde and Wanapum Basalts (Stop 2)

Figure 14. Photograph of pillow lava north of Dayton (Stop 2)

Figure 15. Diagrammatic cross section of the upper Tucannon River valley

Figure 16. Photograph of terracettes on the side of the Tucannon River valley

Figure 17. Photograph of Touchet Beds in a roadcut just northwest of Starbuck (Stop 3)

Figure 18. Photograph of the contact between two rhythmites in the Touchet Beds

Figure 19. Sketch of some characteristics of the Touchet Beds

Figure 20. Photograph of the Snake River at the mouth of the Tucannon River

Figure 21. Part of the Starbuck 15-minute topographic map showing Missoula floods features

Figure 22. Photograph of the Snake River from southeast of Lyons Ferry

Figure 23. Photograph of the Snake River between the Tucannon and Palouse Rivers

Figure 24. Photograph of the lower Palouse River at the Marines Rockshelter

Figure 25. Photograph of scabland topography along the lower Palouse River

Figure 26. Photograph of streamlined loess hills southwest of Palouse Falls State Park

Figure 27. Photograph of the canyon of the Palouse River

Figure 28. Geologic cross section at Palouse Falls

Figure 29. Photograph of Palouse Falls (Stop 5)

Figure 30. Photograph of the Channeled Scabland at the head of HU or Davin Coulee

Figure 31. Photograph of a gravel bar on the floor of Washtucna Coulee

Figure 32. Photograph of Washtucna Coulee at an ancestral meander

Figure 33. Photograph of Devils Canyon

Figure 34. Diagrammatic cross section of intracanyon flows on the east side of Devils Canyon

Figure 35. Photograph of three intracanyon flows on the west side of Devils Canyon (Stop 6)

Figure 36. Geologic cross section near Lower Monumental Dam

Figure 37. Photograph of giant ripple marks at Lower Monumental Dam

Figure 38. Photograph of basalt flow overlying gravels south of Lower Monumental Dam (Stop 7)

Figure 39. Photograph across the Snake River at Scott gravel bar

Figure 40. Topographic map showing surficial geology at the leading edge of the Juniper Dunes

Figure 41. Photograph of the northern part of the Juniper Dunes

Figure 42. Photograph of transverse dunes, Juniper Dunes Wilderness

Figure 43. Photograph of parabolic dunes, Juniper Dunes Wilderness

Figure 44. Photograph of Ice Harbor Dam

Figure 45. Photograph of a view down the Snake River from Ice Harbor Dam

Figure 46. Diagrammatic cross sections of the basalts near Ice Harbor Dam

Figure 47. Photograph of Saddle Mountains Basalt east of Ice Harbor Dam (Stop 8A)

Figure 48. Photograph of an invasive flow east of Ice Harbor Dam (Stop 8B)

Figure 49. Photograph of a tuff cone west of Ice Harbor Dam (Stop 9A)

Figure 50. Photograph of tuff breccia west of Ice Harbor Dam (Stop 9A)

Figure 51. Photograph of flows and dike west of Ice Harbor Dam (Stop 9B)

Figure 52. Photograph of Wallula Gap and the delta of the Walla Walla River

Figure 53. Photograph of Wallula fault zone east of Wallula Gap

Figure 54. Photograph of fault at Wallula (Stop 10)

Figure 55. Close-up photograph of the fault at Wallula (Stop 10)

Figure 56. Photograph of Wallula Gap on the Columbia River

Figure 57. Photograph across the Columbia River at Two Sisters

Figure 58. Photograph of Two Sisters, Wallula Gap

Figure 59. Photograph of alluvial fan and talus at the Washington-Oregon state line (Stop 12)

Figure 60. Photograph of the west side of Wallula Gap near the Washington-Oregon border

Figure 61. Photograph of the Olympic-Wallowa lineament east of Wallula Gap

Figure 62. Cross section of the lower Walla Walla River valley

Figure 63. Diagram of north roadcut at Divide

Figure 64. Photograph of unconformities at Divide (Stop 13)

Figure 65. Photograph of Mount St. Helens set S tephra in Touchet Beds north of Touchet

Figure 66. Photograph of clastic dikes in Touchet Beds north of Touchet (Stop 14)

Figure 67. Photograph of Touchet Beds in the Little Grand Canyon south of Lowden

Figure 68. Photograph of a view northwest of Little Grand Canyon south of Lowden

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WASHINGTON DEPARTMENT OF NATURAL RESOURCES
Jennifer M. Belcher — Commissioner of Public Lands
Kaleen Cottingham — Supervisor

DIVISION OF GEOLOGY AND EARTH RESOURCES
Raymond Lasmanis — State Geologist
J. Eric Schuster — Assistant State Geologist
William S. Lingley, Jr. — Assistant State Geologist

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Washington Department of Natural Resources
Division of Geology and Earth Resources
P.O. Box 47007
Olympia, WA 98504-7007

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Flood Basalts and Glacier Floods: Field Trip Guide to the Geology of Parts of Walla Walla, Franklin, and Columbia Counties, Washington

Robert J. Carson and Kevin R. Pogue
Department of Geology
Whitman College
Walla Walla, WA 99352

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