We often talk about landscape evolution (and
I have a little history on the subject). However, we usually forget that from 65Ky and 12Ky of years ago a lot of our Earth was covered by a glaciation. The image below, robbed from a Mr. Kurt Werth presentation at "At North of Trento and South of Bolzano"
(1,2,3) Meeting, illustrates the situation in the place where I live, the river Adige basin.
I do not know which is the precision of the map, but it illustrates clearly which was the geneal situation. Cause of this, many of the geomorphic features we see nowadays where created by the glacier retreat and by subsequent land-sculpting. Alluvial fans (some hundreds of them) were formed later. Big rock avalanches (according also to isotopic measurements) crumbled down among 10Ky and 3Ky ago.
Therefore it is time that alpine geomorphology (and modelling) put
Paraglacial situations inside its horizon. Actual landslides and sediment production is strongly affected by what the glaciers left.
Reference
Ballantyne, C.K. -
Paraglacial geomorphology, Quaternary Science Reviews 21 (2002) 1935–2017
The role of quaternary glacial processes on landscape evolution is an important aspect of geomorphic analysis in the Pacific Northwest region of the US. Present day alluvial processes continue to respond to conditions resulting from continental and subsequent alpine glaciations. The development of flood and channel migration hazard mitigation strategies by local agencies benefits from a thorough understanding of the dynamic nature of process rates associated with alluvial landscape formation and the nature of these changes over time.
ReplyDeleteBelow is a link to a interesting and useful investigation of Puget Sound Region river valley process domains and their relation to Pleistocene glaciation.
http://riverhistory.ess.washington.edu/pubs/Collins_Montgomery_2011.pdf
By Chase Barton