By Richard Chiverrell
Spring??? well allegedly, let’s call it March, and a chilly Saturday in March, Janet Hooke and Rich Chiverrell set off for the arctic wastes of the Howgill Fells to entertain the final year undergraduates on our ENVS372 Fluvial Environments module. 2.5 hours up the M6 to Tebay at a measured 62 miles per hour we eventually arrived at the foot of Carlingill. The aim was to examine sites along Carlingill valley that illustrate the two main themes of the day’s work:
1) The post-glacial landform sequence, and its relation to Late Pleistocene and Holocene variations in the sediment system.
2) The dynamics of the modern landform system and its relation to the modern sediment system.
The landscape we explored preserves a record of the geomorphic response to environmental change over the period since the Last Glacial Maximum, as we followed if the footsteps of Emiritus Professor of the University of Liverpool Adrian Harvey. The Howgills form a deeply dissected upland in folded Silurian mudrocks, with a relief range of 100-660m, within the headwaters of the River Lune. Evidence for the Late Pleistocene – Holocene sequence of landform evolution comes from (a) morpho-stratigraphic relationships between landforms and sediments, (b) soil chronosequences, (c) radiocarbon dates of several critical sites, especially of buried soils, and (d) the environmental context provided by the peat stratigraphy at Archer Moss from the summits of the Howgill Fells.
In the afternoon the fieldclass tested some of these relationships:
1. Using lichenometry, the growth rate of a lichen called Rhizocarpon geographicum, to assess the age of gravel bars on the floodplain/ How quickly and regularly does the river move?
2. Assessing the maturity of soils on different landforms that range in age from the end of the last ice age ~ 18,000 years ago to 100 years ago.
3. Assessing the impact of varying supply of sediment from the hillslopes (stream-coupled gullies) and the response of the channel to sediment load (you can’t beat a bit of braiding….).
The journey back was uneventful marred only by events taking place in Cardiff…..
Further reading on the geomorphology of the Howgill Fells
CHIVERRELL, R.C., HARVEY, A.M. and FOSTER, G.C., 2007. Hillslope gullying in the Solway Firth – Morecambe Bay region, Great Britain: Responses to human impact and/or climatic deterioration? Geomorphology, 84(3-4), pp. 317-343.
CHIVERRELL, R.C., HARVEY, A.M., HUNTER (NÉE MILLER), S.Y., MILLINGTON, J. and RICHARDSON, N.J., 2008. Late Holocene environmental change in the Howgill Fells, Northwest England. Geomorphology, 100(1-2), pp. 41-69.
HARVEY, A.M., 2012. The coupling status of alluvial fans and debris cones: A review and synthesis. Earth Surface Processes and Landforms, 37(1), pp. 64-76.