Different types of trimlines exist, dependent on the length of time since the last glacial advance . In recently glaciated valleys, they are marked by a distinct change in vegetation. Above the trimline, dense vegetation exists with species characteristic of the region[2,3]. And below the trimline, valley sides are characteristic of bare, ice-scoured rock, or with early stages of vegetational development [2,3]. These are termed ‘Vegetational Trimlines‘, and are commonly associated with glacial activity since the Little Ice Age, within the historical era [2,3].
For older glaciations, occurring prior to the Little Ice Age, the vegetation change may be less distinctive as vegetation succession has occurred [2,4]. Therefore, these trimlines mark the boundary between the smooth, ice-scoured bedrock below the trimline, and the frost-shattered regolith from periglacial weathering above . These can be termed ‘Peri-glacial Trimlines’ [2,3,5].
What are Trimlines Used For?
Unlike other glacial landforms which show the lateral extent, or behaviour of a past glaciations, trimlines mark the maximum vertical extent of the ice surface [3,4]. This enables the production of 3-D model reconstructions of ice sheets and valley glaciers[4,6].
In currently occupied glacial regions, trimlines can be compared to the modern ice surface elevation to assess the role of ice surface thinning, and responses to climate change .
 McCarroll D. (2014) Trimline. In: Encyclopedia of Planetary Landforms. Springer, New York, NY. doi.org/10.1007/978-1-4614-9213-9_383-1
 Benn, D.I., and Evans, D.J.A., 2010. Glaciers and Glaciation. Hodder-Arnold, London
 Rootes, C.M., and Clark, C.D. (2020) Glacial trimlines to identify former ice margins and subglacial thermal boundaries: A review and classification scheme for trimline expression. Earth-Science Reviews. 210. 103355.
 McCarroll, D. (2016) Trimline Trauma: The wider implications of a paradigm shift in recognising and interpreting glacial limits. Scottish Geographical Journal. 132(2).
 Ballantyne, C. K. (1997). Periglacial Trimline in the Scottish Highlands. Quaternary
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 Ballantyne, C. K. (2010). Extent and Deglacial Chronology of the Last British‐Irish Ice Sheet: Implications of Exposure Dating Using Cosmogenic Isotopes. Journal of Quaternary Science, 25(4), 515–534.
 Kohler, J., James, T., Murray, T., Nuth, C., Brandt, O., Barrand, N., Aas, H. & Luckman, A.
(2007). Acceleration in Thinning Rate on Western Svalbard Glaciers. Geophysical Research