By Dorothy H. Radbruch-Hall, Roger B. Colton, William E. Davies, Ivo Lucchitta, Betty A. Skipp, and David J. Varnes
The landslide map indicates regions where slope-stability problems should be considered in large-scale national planning, for example in evaluating areas suitable for nuclear reactors, solid-waste disposal, large surface-mining operations, or major water-development projects. The map shows areas of landslides and areas susceptible to future landsliding in the conterminous United States. Because the map is highly generalized, however, it is not suitable for use in local planning or actual site selection. On this map, landslides are considered to be any downward and outward movement of earth materials on slopes (see Varnes, 1958). Talus deposits, formed by the falling or rolling of individual rocks downhill, are not considered landslides, unless the deposits themselves are thought to be moving. Other deposits of gravitational origin that are not considered include: Tertiary megabreccias (deposits resulting from ancient landslides not related to present slopes), large gravitational thrust sheets, solifluction deposits, snow avalanches, and debris deposited by flows that contribute to alluvial fans in arid regions. In preparing the landslide map, units shown on the Geologic Map of the United States (King and Beikman, 1974) were evaluated in two categories of susceptibility and three categories of approximate incidence (amount) of landslides. Susceptibility is not shown where it is comparable to incidence – for example, where areas of the highest category of incidence are assumed to have high susceptibility and where areas of the lowest category are assumed to have low susceptibility. Susceptibility to landsliding is defined as the probable response of the rocks and soils to natural or artificial cutting or loading of slopes or to anomalously high precipitation. The effect of earthquakes on slope stability is not evaluated. If susceptibility of a formation is known to be very high although incidence is low, as, for example, in the flat areas underlain by the Pierre Shale in the northern Great Plains (Upper Missouri Basin), the susceptibility may be two categories higher than the incidence. This situation is in contrast to that in the Coast Ranges in California where natural incidence is moderate to high, and, in general, susceptibility is not appreciably greater than indicated by the natural incidence.
The 8- or 10-inch precipitation isolines are shown on the map because landslides are generally few where precipitation is less than 8 or 10 inches per year. In some arid regions, landslides may be abundant where precipitation is less than 8 or 10 inches per year, but susceptibility to future natural landsliding is low, because much landsliding in now arid regions took place during Pleistocene time, when precipitation was heavier than at present.
Landsliding is related to the physiographic characteristics of an area inasmuch as the geological factors that influence slope stability also influence the form of the land surface. Therefore, certain physiographic regions in the United States – such as the Coast Ranges in California, the Colorado PIateau, The Southern Rocky Mountains, and the Appalachians (Eastern Highland Division) – are more slide prone than others.
Pronounced physical differences among the areas of high landslide incidence are not apparent on the map. In the Coast Ranges in California, landslides occur mainly in highly sheared rock of the Franciscan assemblage and in poorly consolidated younger (Tertiary) sedimentary rocks. Landslldes include both small but damaging debris flows that form at times of intense rainfall, as well as slumps and earth flows, some of which are more than 200 feet deep and cover many square miles. On the Colorado Plateau, large landslides are primarily slumps and block slides that occur where shales or other relatively soft rocks are interbedded with or overlain by more resistant rocks such as basalt, sandstone, or limestone. The Southern Rocky Mountains are complex in rock type and climate, so the landslides there are also complex. The landslides range from rock falls at one extreme to slumps and debris flows at the other. The slide-prone areas include ridgetop grabens associated with uphill-facing scarps (sackungen), both features of gravitational origin. Landslide susceptibility and incidence may appear more extensive for Colorado than for some other States, because large-scale maps of landslides in Colorado have been prepared from interpretation of aerial photography and other data (Cotton and others, 1976, Publication no. 28 below). The map below is a reproduction of the landslide map of Colorado.
In the Appalachians, many slide-prone areas are characterized by shallow landslides of large areal extent in weathered rock or colluvium. These deposits may cover many thousands of square feet but are generally less than 10 feet deep. The colluvium covers many types of bedrock, so the map designations of incidence and susceptibility cut across formational boundaries. Slow-moving earthflows and debris slides are abundant, but the greatest damage and loss of life result from debris flows and avalanches when persistent rainfall is followed by sudden heavy rainfall. The map compilation shows that, in general, fine-grained clastic rocks – those consisting predominantly of silt- and clay-sized particles – are most prone to landsliding, especially if they are poorly consolidated and/or are interbedded with or overlain by more resistant but fractured and permeable rocks such as limestone, sandstone, or basalt. Sliding is also extensive in highly sheared rocks. Loose slope accumulations of fine-grained surface debris anywhere are liable to slide, particularly at times of intense precipitation. Steep slopes facilitate landsliding, and thus many slide-prone areas in the United States are in mountainous regions, although slope alone is not indicative of susceptibility to landsliding; commonly, steep slopes in hard unfractured homogeneous rocks may be stable. If, however, slopes are currently being steepened or undercut – along active faults, wave-cut cliffs, and vigorously eroding streams, or in manmade cuts – they may be unstable, particularly in soft rock.
|Map of Alaska and Hawaii (Data not available)|
The following publications describing landslides of special interest are keyed to areas on the map.
1. Jones, F. O., Embody, D. R., and Peterson, W. L., 1961, Landslides along the Columbia River valley, northeastern Washington: U.S. Geological Survey Professional Paper 367, 98 p.2. Crandell, D. R., 1969, Surficial geology of Mount Rainier National Park, Washington: U.S. Geological Survey Bulletin 1288, 41 p.
3. North, W. B., and Byrne, J. V., 1965, Coastal landslides of northern Oregon: The Ore Bin, v. 27, no. 11, p. 217-241.
4. Robinson, Paul T., 1975, Reconnaissance geologic map of the John Day Formation in the southwestern part of the Blue Mountains and adjacent areas, north-central Oregon: U.S. Geological Survey Miscellaneous Investigations Map l-872.
5. Anderson, R. A., Jr., and Schuster, Robert L., 1970, Stability of slopes in clay shales interbedded with Columbia River Basalt, in Engineering Geology and Soils Engineering: Idaho Department of Highways, p. 273-280, lllus. (including sketch map).
6. Huffman, M. E., Scott, R. G., and Lorens, P. J” 1969, Geologic investigation of landslides along the Middle Fork Eel River, California (abs.): Geological Society of America, Abstracts with programs for 1969, pt. 7, p. 111-112.
7. Foster, D. F., 1933, Treacherous slides delay Cloverdale-Hopland realignment: Pacific Street and Road Builder, v. 32, no. 2, p. 13-15. Radbruch-Hall, Dorothy H., 1976, Maps showing areal slope stability in a part of the northern Coast Ranges, California: U.S. Geological Survey Miscellaneous Investigations Map 1-982, scale 1:62,500.
7a. Thompson, G. A., and White, D. E., 1964, Regional geology of the Steamboat Springs area, Washoe County, Nevada: U.S. Geological Survey Professional Paper 458-A, 52 p. Tabor, R. W., and Ellen, S., 1975, Washoe City folio, geologic map: Nevada Bureau of Mines and Geology Environmental Series, Washoe Lake area.
8. Krauskopf, K. B., Feitler, S., and Griggs, A. B., 1939, Structural features of a landslide near Gilroy, California: Journal of Geology, v. 47, no. 6, p. 630-648.
9. Burchfiel, B. C., 1966, The Tin Mountain landslide and the origin of megabreccia: Geological Society of America Bulletin, v. 77, p. 95-100.
10. Campbell, R. H., 1975, Soil slips, debris flows, and rainstorms in the Santa Monica Mountains and vicinity, southern California: U.S. Geological Survey Professional Paper 851, 51 p.
11. Sharp, R. D., and Nobles, L. H., 1953, Mudflow of 1941 at Wright wood, Southern California: Geological Society of America Bulletin, v. 64, p. 547-560.
12. Shreve, R. L., 1968, The Blackhawk Landslide: Geological Society of America Special Paper 108, 47 p.
13. Easton, W. H., 1973, Earthquakes, rain, and tides at Portuguese Bend Landslide, California: Bulletin, Association of Engineering Geologist v. 10, no. 3, p 1 73-194.
Merriam, R. H., 1960, Portuguese Bend Landslide, Palos Verdes Hills, California: Journal of Geology, v. 68, no. 2, p. 140-153.
14. Blanc, R. P., and Cleveland, G. B., 1968, Natural slope stability as related to geology, San Clemente area, Orange and San Diego Counties, California: California Division of Mines and Geology, Special Report 98, 19 p.
15. Mudge, M. R., 1965, Rockfall-avalanche and rockslide-avalanche deposits at Sawtooth Ridge, Montana: Geological Society of America Bulletin, v. 76, p. 1003-1014.
16, 17. Fleming, R. W., Spencer, G. S., and Banks, D. C., 1970, Empirical study of behavior of clay shale slopes: U.S. Army Engineer Nuclear Cratering Group, Technical Report 15, 2 v.
18. Waldrop, H. A., and Hyden, H. J., 1963, Landslides near Gardiner, Montana, in Geological Survey research 1962: U.S. Geological Survey Professional Paper 450-E, p. E11-E14.
19. Hadley, J. B., 1964, Landslides and related phenomena accompanying the Hebgen Lake earthquake of August 17, 1959: U.S. Geological Survey Professional Paper 435, p. 107-138.
20. Dupree, H. K., and Taucher, G. J., 1974, Bighorn Reservoir landslides, south-central Montana, in Voight, Barry, ed., Rock mechanics: the American Northwest: Pennsylvania State University, p. 59-63.
21. Pierce, William G., 1968, The Carter Mountain landslide area, northwest Wyoming, in Geological Survey research 1968: U.S. Geological Survey Professional Paper 600-D, p. D235-D241.
34. Strahler, A. N., 1940, Landslides of the Vermillio n and Echo Cliffs, northern Arizona: Journal of Geomorphology, v. 3, no. 4, p. 285-301.
35. Harrison, T. S., 1927, Colorado-Utah salt domes: American Association of Petroleum Geologists Bulletin, v. 11, p. 111-133.
Lewis, R. Q., and Campbell, R. H., 1965, Geology and uranium deposits at Elk Ridge and vicinity, San Juan County, Utah: U.S. Geological Survey Professional Paper 474-B, p. B1-869. Colton, R. B., Williams, P., and Hansen, W. R., 1975, written communication.
36a, b, Varnes, H. D., 1949, Landslide problems of southwestern Colorado: U.S. Geological Survey Circular 31, 13 p.
37. Crandell, D. R., and Varnes, D. J., 1961, Movement of the Slumgullion earthflow near Lake City, Colorado, in Geological Survey research 1961: U.S. Geological Survey Professional Paper 424-8, p. B136-8139.
Howe, Ernest, 1909, Landslides in San Juan Mountains, Colorado: U.S. Geological Survey Professional Paper 67, 58 p.
38. . Reiche, Parry, 1937, The Toreva-block, a distinctive landslide type: Journal of Geology, v. 45, no. 5, p. 538-548.
39. Watson, R. A., and Wright, H. E., Jr., 1963, Landslides on the east flank of the Chuska Mountains, northwestern New Mexico: American Journal of Science, v. 261, p. 525-548.
40. Lemke, R. W., 1960, Geology of the Souris River area, North Dakota: U.S. Geological Survey Professional. Paper 325, 138 p.
41, 42. Fleming, R. W., Spencer, G. S., and Banks, D. C., 1970, Empirical study of behavior of clay shale slopes: U.S. Army Engineer Nuclear Cratering Group Technical Report 15, 2 v.
43. Robinson, C. S., Mapel, W. J., and Bergendahl, M. H., 1964, Stratigraphy and structure of the northern and western flanks of the Black Hills uplift, Wyoming, Montana, and South Dakota: U.S. Geological Survey Professional Paper 404, 134 p.44. Cattermole, J. M., 1972, Geologic map of the Rapid City East Quadrangle, Pennington County, South Dakota: U.S. Geological Survey Geologic Quadrangle Map GQ-986.
45. Crandell, D. R., 1952, Landslides and rapid-flowing phenomena near Pierre, South Dakota: Economic Geology, v. 47, no. 5, p. 548-568.
46. Scully, John, 1973, Landslides in the Pierre Shale in central South Dakota: South Dakota Department of Transportation, State Study 635(67), 707 p.
47. Erskine, C. F., 1973, Landslides in the vicinity of the Fort Randall Reservoir, South Dakota: U.S. Geological Survey Professional Paper 675, 64 p.
48. Lohnes, R. A., and Handy, R. L., 1968, Slope angles in friable loess: Journal of Geology, v. 76, no. 3, p. 247-258.49. Whitney, C. S., 1936, Stabilizing a Lake Michigan bluff: Civil Engineering, v. 6, no. 5, p. 309-313.
50. Miller, R. D., 1964, Geology of the Omaha-Council Bluffs area, Nebraska-lowa: U.S. Geological Survey Professional Paper 472, 70 p.
51. Brown, C. E., and Whitlow, J. W., 1960, Geology of the Dubuque South quadrangle, lowa-lllinois: U.S. Geological Survey Bulletin 11 23-A, 93 p.52. DuMontelle, P. B., and others, 1971, Landslides along the Illinois River Valley south and west of LaSalle and Peru, lllinois: lllinois State Geological Survey, Environmental Geology Notes no. 48, 16 p.
53. Goodfield, A. G., 1970, Rockfalls and landslides along State Highway 79 at Clarksville, Missouri: Annual Highway Geology Symposium, 21st, 1970, Proceedings, p. 19-28.
54. Anonymous, 1972, The bluff collapse on the Gasconade: Missouri Mineral News, v. 12, no. 6, p. 104-105.
55. Hayes, C. J., 1971, Landslides and related phenomena pertaining to highway construction in Oklahoma, in Rose, W. D., ed., Environmental aspects of geology and engineering in Oklahoma: Oklahoma Academy of Science Annals., Publication 2, p. 47-57.
56. Fuller, M. L., 1912, The New Madrid earthquake: U.S. Geological Survey Bulletin 494, 119 p.
57. Turnbull, W. J., Krinitzsky, E. L., and Weaver, F. J., 1966, Bank erosion in soils of the Lower Mississippi Valley: American Society of Civil Engineers Proceedings, v. 92, SM1, p. 121-136.
58. Vestal, F. E., 1942, Adams County mineral resources: Mississippi State Geological Survey Bulletin 47, p. 42.
59. Wright, S. G., and Duncan, J. M., 1972, Analyses of Waco Dam slide: American Society of Civil Engineers Proceedings, v. 98, no SM9, p. 869-877.
60. Brunsden, Denys, and Kesel, R. H., 1973, Slope development on a Mississippi River bluff in historic time: Journal of Geology, v. 81, p. 576-597.
61. Stanley, D. J., and others, 1966, Mississippi River bank failure, Fort Jackson, Louisiana: Geological Society of America Bulletin, v. 77, p. 859-866.
62. Flaccus, Edward, 1958, White Mountain landslides: Appalachia, v. 32, no. 127, p. 1 75-191.
63. Morse, Edward S., 1868, On the landsliding in the vicinity of Portland Maine: Proceedings, Boston Society of Natural History, v. 12, p. 235-244.
64. Electrical World, 1956, Major rock slide buries Scholellkopf power station: v. 145, June 19, p. 8-9.65. Newland, David H., 1916, Landslides in unconsolidated sediments: with a description of some occurrences in the Hudson Valley: New York State Museum Bulletin 187, p. 79-105.
66. Briggs, Reinald P., Pomeroy, John S., and Davies, William E., 1975, Landsliding in Allegheny County, Pennsylvania: U.S. Geological Survey Circular 728, 18 p.
67. Davies, William E., 1975, Personal observation, McMechen, West Virginia. On March 8, 1975, a prehistoric landslide of large dimension was reactivated with no apparent cause, on a long valley wall scarp on the east side of McMechen. The present earthflow is 454 m across the face of the slope and 304 m long downslope. The valley wall, which is typical of those that border much of the Ohio River, has a slope of 20’-30’ and 122 to 153 m of relief. The earthflow is in silty, clayey colluvium 3 m or less in thickness overlying shale and sandstone of the upper Monongahela Group (Pennsylvanian). The slide is very shallow, averaging 1.2 m to 2.4 m thick, and has caused severe damage to 50 houses by shearing across the upper part of the foundations. Movement is approximately 1 m downslope per year.
68. Von Schilichten, Otto C., 1935, Landslide in the vicinity of Cincinnati: The Compass, v.15, no.3, p. 151-154; and Davies, William E., personal observation.
69. Stringfield, V. T., and Smith, R. C.,1956, Relation of geology to drainage, floods, and landslides in the Petersburg area, West Virginia: West Virginia Geological and Economic Survey, Report of Investigation 13, 19 p.; and Davies, William E., personal observation.
70. Herbold, Keith D., 1972, Cut slope failure in residual soil: Annual Highway Geology Symposium, 23d, Hampton, Virginia, 1972, Proceedings, p. 33-49.
71. Froelich, Albert J., 1970, Geologic setting of landslides along Pine Mountain, Kentucky: Highway Research Record, no. 323, p. 1-5.
72. Leith, C. J., and others, 1965, An investigation of the stability highway cut slopes and embankments in North Carolina: Highway Research Programs, Engineering Research Department, North Carolina State University, Project ERD-110-U, Final Report, p. 22-23.
73. Jordan, Richard H., 1949, A Florida landslide: Journal of Geology, v. 57, no. 4, p. 418-419.
Colton, R. B., Lemke, R. W., and Lindvall, R. M., 1961, Glacial map of Montana east of the Rocky Mountains: U.S. Geological Survey Miscellaneous Geologic Investigation Map 1-327. Scale 1:500,000.
Crandell, D. R., 1965, The glacial history of western Washington and Oregon, in Wright, H. B., Jr., and Frey, D. G., The Quaternary of the United States: Princeton University Press, p. 341-353.
King, P. B., and Beikman, H. M., 1974, Geologic map of the United States: (exclusive of Alaska and Hawaii) U.S. Geological Survey, scale 1:2,500,000; also in The National Atlas of the United States, scale 1:7,500,000.
National Oceanic and Atmospheric Administration, 1974, Climates of the States: Port Washington, N. Y., Water Information Center, Inc., 2 v.
National Research Council, 1945, Glacial map of North America: New York, N.Y., Geological Society of America, scale 1:4,55S,000.
Varnes, D. J., 1958, Landslide types and processes, in
Eckel, E. B., ed., Landslides and engineering practice: Highway Research Board,
Special Report 29, NAS-NRC Publication 544, p. 20-47.
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