Hong Meigui Zhongdian Draughting Holes 2006 was a 4-person, 24-day expedition to the mountains just west of the town of Zhongdian, Yunnan Province, China.
This expedition was part of an ongoing project whose aim is to find caves of world-class depth. Previous expeditions to the same area (Hong Meigui Yunnan 2001, 2002 [HMG02], 2003 [HMG03], Resurgences 2004, 2004 [HMG04], 2005 [HMG05]) had logged some 401 caves in the Zhongdian mountains, most at altitudes in excess of 4000m. The area drains to resurgences in the adjacent Yangtze valley, at 2000m ASL.
However, despite the number of cave features and the phenomenal depth potential, it was proving very difficult to find caves of depths in excess of 50m. The main reasons for this were the vastness of the area, and the fact that the majority of entrances choke within 10m.
Expeditions elsewhere in the world have found that a highly efficient way of locating entrances to caves of significant volume is often to visit the area of interest when it has light snow cover. The point here is that, in the winter, cave air is typically warmer than air on the surface and, in particular, tends to remain above freezing point; further, caves of significant volume often emit a draught. Because of these two factors, it is common to find gaps in the snow at significant cave entrances, where the warm draught has melted the snow cover. This means that it is sometimes far easier to identify caves of interest in the winter than in the summer, despite the increased difficulties of moving around the mountain.
The purpose of the 2006 expedition was therefore to visit the area when it was expected to have light snow cover, and to log the locations of ‘draughting holes’. We hoped that this would enable us to identify caves that deserved further attention, so that the efforts of future summer expeditions could be focussed in the most fruitful places.
In the event, however, the expedition’s plan was thwarted by the fact that when we arrived in Zhongdian, there was no snow on the mountaintops (for the first time in living memory, at this time of year!). We therefore changed plan, and carried out a recce of an area identified as interesting by the Yunnan 2004 expedition (north of the ‘Northern Camp’ visited in 2004). Towards the end of the expedition (and following snowfall), we returned to the Ye Kang area. Some new caves were found, but none of great significance. Findings and suggestions for future work are summarized below.
The expedition’s logistics were sufficiently similar to those of summer expeditions to the area that details are not duplicated here; for the details, see, e.g., the 2004 report [HMG04].Commentaires :