Ice-avalanche impact landforms: The event in 2003 at the glacier n?rdliches bockkarkees, hohe tauern range, Austria

摘要

The hanging glacier N?rdliches Bockkarkees (47°07′21″N; 12°44′00″E) represents the only Austrian glacier that formed large and hazardous ice avalanches over the last decades. Only one major ice avalanche was released between August 1993 and July 2011 underlying the rareness of such large ice avalanches in the Austrian Alps. The ice avalanche happened on 26 June 2003 and was very unusual for two reasons: First, the ice avalanche occurred suddenly without major signs of glacier instabilities even a few days before the event. Second, the ice avalanche was released very early in the season. Ice and debris with a volume of 300000m ~3 avalanched over a vertical distance of 1200m. The main deposits with a volume of 250000m ~3 and a debris content of 10% formed a flat avalanche cone in the K?fer Valley covering 82000m ~2. This paper focuses on geomorphic and glaciological field measurements and observations at and below the ice avalanche deposit and its vicinity after the event. Studies were made (a) at the deposited material itself, (b) at the reshaped land surface below the deposit after ice melt, (c) at the front and margin of the deposit, and (d) outside the deposit. Our study reveals different types of ice-avalanche impact landforms comparable to landforms caused by snow avalanches. It is shown that ice avalanches charged with debris at the N?rdliches Bockkarkees are important in forming and reshaping erosional and depositional landforms along the track. However, the conservation potential of these landforms is low.