Permafrost

within the tested area. The inventory was not an exhaustive list of all the slope instabilities in
the area, but an inventory of all areas showing any kind of signal on ERS-SAR interferograms,
that can be interpreted as a possible slope movement.
The resulting inventory of ERS-InSAR-detected instabilities can be seen as a preliminary
tool compiled at regional scale which can be useful for further investigations to be carried out
(if required) at local scale. It appears to be an attractive perspective both for early natural hazard
management and process understanding of slope movement in permafrost areas.
Keywords: SAR interferometry, permafrost, slope instabilities, rock glacier
106
Active Lag Block Streams in the Chinese Tian Shan
Stuart A. Harris, Guodong Cheng, Cui Zhijiu
(1.Department of Geography, University of Calgary, T2N 1E4, Canada;
2.Cold and Arid Regions Environmental and Engineering Research Institute, Lahnzou, China,
730000; 3. Department of Geography, Peking University, Beijing, China.)
Abstract: Active lag block streams are forming today in the mountains of the Chinese Tian
Shan above treeline near cold-based glaciers. Mean annual air temperatures are below –5.4°C
while the mean annual precipitation exceeds 420mm. This paper describes the three main
types of situation in which they occur (drainage from a hanging valley, gullies on a steeply
sloping valley wall, and in front of an end moraine), together with their characteristics.
Conditions favoring their formation include continuous permafrost, sediments with abundant
large blocks, incipient sorted patterned ground, a discontinuous vegetation cover, steep slopes,
high precipitation and a fairly thick winter snow cover. Once started, washing out of the finer
interstitial material leaving behind the blocks will occur with every spring snow melt and heavy
precipitation event. These results are important since they appear to provide the first
description of active lag block streams being formed. Lag block streams are rather common in
many parts of the world, but their conditions of formation have been the subject of considerable
debate in the absence of any known modern analogues.
Key words: Active lag block streams, Tian Shan, continuous permafrost, sorted patterned
ground, end moraines, permafrost hydrology.
Exposed glacial and debris-covered ice in the Hindu Kush, Afghanistan.
Umesh Haritashya, John Shroder, Michael Bishop, Henry Bulley, Jeffrey Olsenholler
GLIMS (Global Land Ice Measurements from Space) Regional Center for Southwest Asia (Afghanistan and
Pakistan), Department of Geography and Geology, University of Nebraska at Omaha, Omaha, NE 68182
USA
Abstract:Snow, glacier ice, and debris-covered glacial and ground ice in Afghanistan are