ABSTRACT
Increasing recognition is being given to the significance of thresholds in geomorphic processes and landform evolution. While research frequently focuses on conditions across a threshold, examination of variability among thresholds may prove equally important. Map variability of the threshold-dependent process, land sliding, and its controlling landscape characteristic-the Franciscan melange-can be examined for expected covariance. Both the landslide, geologic, and landslide/geologic maps have the General Land Office grid showing sections of one-mile square areas. The spatial distribution of threshold events and related, or controlling, landscape characteristics may be important for understanding how a process is affecting evolving landforms. D.J. Varnes examined covariance among map units for engineering geology maps. Many of the analytical techniques used were graphical or tabular methods. The normal generated distribution offers a statistical technique for examining variability among map units. Threshold-dependent processes causing episodic erosion are important elements requiring study to refine our understanding of landform evolution.
