MOUNTAIN GEOMORPHOLOGY: THE DRIVERS OF CHANGE AT DIFFERENT SCALES

A new scale typology for mountain geomorphology is introduced. Here we propose a scale typology consisting of four distinct time and space scales to characterize mountain environments world-wide. The rationale is that tectonics and climate have been most important at the largest scale and in the longest evolving mountain systems (scales of >10⁸ yr and >10⁶ km²); glaciation superimposed its effects on tectonics, lithology and climate at scales of order 10⁶ yr and order 10⁴ km²; paraglaciation, defined as “non-glacial processes conditioned by glaciation”, has modified glaciated mountain systems at scales of order 10⁴ yr and 10² km²); and finally, at century and 1 km² scales, local relief, hydroclimate and human activity are presently acting on paraglacial forms. The time scales involved are respectively equivalent to the Tertiary Period, the Quaternary Period, the Holocene Epoch and the Anthropocene Epoch. All time and space scales are expressed as orders of magnitude. Although this typology admits many exceptions it provides valuable guidelines for reconciling seemingly contradictory conclusions from literature in which scale effects are commonly ignored.

In the case of mountain environments which have not been overridden by ice, a similar typology remains relevant with intense periglaciation replacing glaciation and paraglaciation defined as “non-glacial processes conditioned by periglaciation”.

The cumulative effect of all drivers (tectonics, climate, lithology, glaciation, paraglaciation, local relief, hydroclimate and human activity) has produced the polygenetic mountain landscape we see today. The text discusses each of the drivers and their interactions in turn.