Welcome to the wonderful world of geomorphology

Monday, October 31, 2011

Tectonics and climate: the great geomorphic battle

The twin controls of climate and tectonics are the major forces shaping the geomorphological landscape around us.  Much recent geomorphic work has gone into clarifying which is the most important, and how they interact.  Many recent studies focus in particular on the relationship between tectonic uplift and climatically-powered denudation in shaping mountains.  There are several good papers you can look at to find more about this topic, but I recommend as a starting point this paper by Egholm et al:

Glacial effects limiting mountain height.
Egholm DL, Nielsen SB, Pedersen VK, Lesemann JE.
Abstract
The height of mountain ranges reflects the balance between tectonic rock uplift, crustal strength and surface denudation. Tectonic deformation and surface denudation are interdependent, however, and feedback mechanisms-in particular, the potential link to climate-are subjects of intense debate. Spatial variations in fluvial denudation rate caused by precipitation gradients are known to provide first-order controls on mountain range width, crustal deformation rates and rock uplift. Moreover, limits to crustal strength are thought to constrain the maximum elevation of large continental plateaus, such as those in Tibet and the central Andes. There are indications that the general height of mountain ranges is also directly influenced by the extent of glaciation through an efficient denudation mechanism known as the glacial buzzsaw. Here we use a global analysis of topography and show that variations in maximum mountain height correlate closely with climate-controlled gradients in snowline altitude for many high mountain ranges across orogenic ages and tectonic styles. With the aid of a numerical model, we further demonstrate how a combination of erosional destruction of topography above the snowline by glacier-sliding and commensurate isostatic landscape uplift caused by erosional unloading can explain observations of maximum mountain height by driving elevations towards an altitude window just below the snowline. The model thereby self-consistently produces the hypsometric signature of the glacial buzzsaw, and suggests that differences in the height of mountain ranges mainly reflect variations in local climate rather than tectonic forces.
Nature. 2009 460:884-7.

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