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PRELIMINARY AGE CLASSIFICATION OF LANDSLIDES FOR INVENTORY MAPPING
Proceedings of the Annual Symposium on Engineering Geology and Soil Engineering (1984)
  • James P. McCalpin
Abstract
A preliminary age classification for landslides is proposed for inventory mapping, based on morphologic criteria visible on aerial photographs. Because landslide scars and deposits are generally disequilibrium landforms, they progress through observable morphologic stages as they age. Four age classes are distinguished: 1) active; 2) inactive-young; 3) inactive-mature; 4) inactive-old. Each age class reflects the age of latest movement only. The morphologic "freshness" of each part of the landslide must be evaluated, including: the head scarp, lateral scarps, marginal drainage, internal scarps and blocks, internal drainage pattern, vegetation type and density, and toe morphology. Morphologic parameters defined from air photos are similar to the morphologic relative-dating (RD) parameters used for glacial deposits, which are also bouldery disequilibrium landforms (Burke and Birkeland, 1979). In addition, cross-cutting relationships between the landslide and other landforms are used for age estimation. The proposed classification has limitations caused by both internal and external factors: 1) Aerial photographs have limited resolution in identifying such small features as tilted ("jackstrawed") trees; 2) Morphologic differences exist among landslide types, which can cause two slides of different type to appear similar, even if of different age; 3) Landslides on surfaces of different aspect or slope are modified at different rates by different dominant slope processes; and 4) It is commonly difficult to obtain absolute ages with which to "calibrate" the age classification.
Keywords
  • landslide,
  • mapping,
  • inventory
Publication Date
1984
Citation Information
James P. McCalpin. "PRELIMINARY AGE CLASSIFICATION OF LANDSLIDES FOR INVENTORY MAPPING" Proceedings of the Annual Symposium on Engineering Geology and Soil Engineering Vol. 21 (1984)
Available at: http://works.bepress.com/james_mccalpin/3/