DEar Rg experts on Landslides
Lithological contact as a controlling factor-------How much will be helpful the spatial relationship between landslides and lithological contact?
regards
Ijaz
To elaborate on Gareth Williams perfectly correct "depends"...
In a circumstance where there is a weak lithologic layer (e.g. a shale or clay) and the bedding planes/lithologic contacts are oriented downslope, sub-parallel to the topography, the the relationship will likely develop as nearly 1 to 1. Conversely, if the lithology is homogeneous in terms of strength and permeability, and the bedding planes/lithologic contacts are oriented orthogonal to the topography, then the relationship will likely be near zero.
That said, topography doesn't tend to develop independent of lithology, bedding, and fractures. Topography is the product of some combination of flowing water (sometimes flowing frozen water in the form of glaciers and ice sheets) and mass wasting (also known as landslides). Wind can play a role in some cases. Because of this, if there are weak layers, the topography will tend to reflect those layers because the topography will to some degree be the product of mass wasting.
The topography can also be fault controlled, but as Matthew Maybe pointed out the action of water will change the topography using the fault as a line of weakness and causing a preferential pathway.
That is an excellent point. I was focused on the sculpting of topography by mass wasting and erosion, but the uplift (and down-drop) of tectonic (and volcanic) forces creates the gradients upon which water erosion and mass wasting are dependent.
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