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High resolution DEMs obtained from LiDAR topographic data have led to improved landform inventories (e.g. landslides and fault scarps) and understanding of geomorphic event frequency. Here we use airborne LiDAR mapping to investigate meltwater pathways associated with the Tweed Valley palaeo ice-stream (UK). In particular we focus on a gorge downstream of Palaeolake Milfield, previously mapped as a sub-glacial meltwater channel, where the identification of abandoned headcut channels, run-up bars, rock-cut terrace surfaces and eddy flow features attest to formation by a sub-aerial glacial lake outburst flood (GLOF) caused by breaching of a sediment dam, likely an esker ridge. Mapping of these landforms combined with analysis of the gorge rim elevations and cross-section variability revealed a two phase event with another breach site downstream following flow blockage by higher elevation drumlin topography. We estimate the magnitude of peak flow to be 1-3 × 10 3 m 3 /s, duration of the event to range from 16-155 days, and a specific sediment yield of 10 7 -10 9 m 3 /km 2 /yr. We identified other outburst pathways in the lower Tweed basin that help delineate an ice margin position of the retreating Tweed Valley ice stream. The results suggest that low magnitude outburst floods are under-represented in Quaternary geomorphological maps. We therefore recommend regional LiDAR mapping of meltwater pathways to identify other GLOFs in order to better quantify the pattern of freshwater and sediment fluxes from melting ice sheets to oceans. Despite the relatively low magnitude of the Till outburst event, it had a significant impact on the landscape development of the lower Tweed Valley through the creation of a new tributary pathway and triggering of rapid knickpoint retreat encouraging new regional models of post-glacial fluvial landscape response.

Part 2: Ethnographic Accounts of IS UseInternational audienceThis paper explores the utility of assemblage theory for intergenerational counter-mapping and, through this, for reconfigurations of indigeneity. Counter-mapping is theorised as a kind of assemblage that, through intergenerational learning, is fundamentally memetic (composed of evolving units of information) in nature. Assemblage is theorised as having three aspects (relations of exteriority, meshworks and memes) for reconfiguring indigeneity in line with spatio-temporal aspects of memes. Counter-mapping assemblages are explored with examples of First Nations’ (indigenous peoples residing in Canada) political and commemorative activity. Kaachewaapechuu, a long commemorative walk in the northern Quebec Cree village of Wemindji, acts as a case study for exploring how assemblages-as-memes can be used to theorise new kinds of counter-mapping that reconfigure indigenous commemoration precisely as political, and therefore as not separate from more media-driven aspects of Canadian politics, including those concerning its First Nations. Global positioning systems and Google Earth mapping platforms were used during the primary author’s participation in kaachewaapechuu, providing for the exploration of new media platforms upon which such a re-theorised politics might be envisioned

This commentary is a direct response to the Forum article ‘Environmentalist thinking and/in geography’ by Radcliffe et al. (2010) . Two main problems are addressed: the perpetuation of a false analogy between cultural and biological evolution, and a misunderstanding of memes. I review the literature and summarize the main issues in cultural and biological evolution and in the related field of memetics, noting ways in which the Forum’s authors’ arguments might be strengthened. In conclusion, some suggestions are made for how geographers might productively engage with innovative ideas from other closely related disciplines.

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