2134/32360
John Hillier
John
Hillier
Ivar Benediktsson
Ivar
Benediktsson
Tom Dowling
Tom
Dowling
Anders Schomacker
Anders
Schomacker
Production and preservation of the smallest drumlins
Loughborough University
2018
Drumlin
Iceland
Mulajokull
Size-frequency distribution
Landform mapping
Subglacial bedform
Morphometry
Earth Sciences not elsewhere classified
Geology
2018-03-26 13:45:52
Journal contribution
https://repository.lboro.ac.uk/articles/journal_contribution/Production_and_preservation_of_the_smallest_drumlins/9482231
Few very small drumlins are typically mapped in previously glaciated landscapes, which might be an important signature of subglacial processes or an observational artefact. 143 newly emergent drumlins, recently sculpted by the Mulajokull glacier, have been mapped using high resolution LiDAR and aerial photographs in addition to field surveying. In this paper, these are
used as evidence that few small drumlins (e.g. height H ≲ 4 m, width W ≲ 40 m, length L ≲ 100 m) are produced; at least, few survive to pass outside the ice margin in this actively forming drumlin field. Specifically, the lack of a multitude of small features seen in other landforms (e.g. volcanoes) is argued not to be due to i) Digital Elevation Model (DEM) resolution or quality, ii) mapper ability in complex (i.e. anthropogenically cluttered or vegetated) landscapes, or iii) post-glacial degradation at this site. So, whilst detection ability must still be at least acknowledged in drumlin mapping, and ideally corrected for in quantitative analyses, this observation can now be firmly taken as a constraint upon drumlin formation models (i.e. statistical, conceptual, or numerical ice flow). Our preferred explanation for the scarcity of small drumlins, at least at sites similar to Mulajokull (i.e. ice lobes with near-margin drumlin genesis), is that they form stochastically during multiple surge cycles, evolving from wide and gentle pre-existing undulations by increasing rapidly in amplitude before significant streamlining occurs.