1 Snow-avalanche impact craters in southern Norway: their morphology and 2 dynamics compared with small terrestrial meteorite craters. 3 4 5 John A. Matthews1*, Geraint Owen1, Lindsey J. McEwen2, Richard A. Shakesby1, 6 Jennifer L. Hill2, Amber E. Vater1 and Anna C. Ratcliffe1 7 8 1 Department of Geography, College of Science, Swansea University, Singleton Park, 9 Swansea SA2 8PP, Wales, UK 10 11 2 Department of Geography and Environmental Management, University of the West 12 of England, Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK 13 14 15 * Corresponding author:
[email protected] 16 17 18 ABSTRACT 19 20 This regional inventory and study of a globally uncommon landform type reveals 21 similarities in form and process between craters produced by snow-avalanche and 22 meteorite impacts. Fifty-two snow-avalanche impact craters (mean diameter 85 m, 23 range 10–185 m) were investigated through field research, aerial photographic 24 interpretation and analysis of topographic maps. The craters are sited on valley 25 bottoms or lake margins at the foot of steep avalanche paths (α = 28–59°), generally 26 with an easterly aspect, where the slope of the final 200 m of the avalanche path (β) 27 typically exceeds ~15°. Crater diameter correlates with the area of the avalanche start 28 zone, which points to snow-avalanche volume as the main control on crater size. 29 Proximal erosional scars (‘blast zones’) up to 40 m high indicate up-range ejection of 30 material from the crater, assisted by air-launch of the avalanches and impulse waves 31 generated by their impact into water-filled craters.