Friday, November 30, 2012

Glacier Caves

The day we made it to Gokyo, we spent the afternoon climbing up the lateral moraine to get our first glimpse of the glacier. It was awe-inspiring. The Ngozumpa is a debris-covered glacier. It is fed in its accumulation zone by avalanches, so the snow contains a lot of rocks/boulders of all sizes. When the upper layers of the ice and rock mixture melt, the rocks (debris) is left over and covers the surface of the glacier.

View north onto the Ngozumpa from the lateral moraine at Gokyo.

Lakes of melt water form on the glacier, exposing ice faces. The drainage of those supra-glacial lakes into lower basins on the glacier is the primary cause for the formation of caves in the ice. (Water streaming across the bedrock under the glacier being another, but those were not caves we were expecting to find on this trip due to the depth of the glacier.) After such a drainage event, cave entrances are often visible in the ice faces of drained lake basins, and this is what we were after. (Entering crevasses or moulins in the hopes of finding caves on debris-covered glaciers does not seem to be a good idea, since inevitable, you will be showered in debris when attempting to do so.) Luckily, we were able to identify several potential cave entrances during this first recon trip, and even a convenient way onto the glacier down the steep moraine -- a few years ago, the trail that leads to Dragnag and the Cho La on the other side of the glacier had moved north about two kilometers and now allowed (relatively) easy access to the glacier directly from our lodge in Gokyo.

During our two weeks in Gokyo, we found a total of four caves that we explored, and investigated a number of other entrances that either didn't go anywhere or appeared to dangerous for us wanting to spend time in them:

Jason explaining the basics of glacier cave relevance for GlacierWorks footage.

Cave #1 had a huge keyhole entrance and was maybe 500-600 meters long. It turned out that Jason had already surveyed this cave in 2009. The cave had experienced several modifications since then, including a new branch of passage that led to another entrance in a different (dry) lake basin. We started a re-survey, and Vickie and I learned the particularities of surveying ice caves: setting survey stations with an ice screw and marking them with paper flags, and being particularly accurate with LRUDs (left-right-up-down measurements from the station). In the meantime, Jason and Pati started measuring the scallops on the cave walls that indicate the direction and flow rate of the water through the cave during the drainage event that created the cave. They soon realized that this cave had experienced too many such events to be useful for the model that Jason was looking to create, and we abandoned the survey.

Cave #2 was a small, nicely decorated room in the dry lake basin that could be reached by a trip through Cave #1. Caves #3 and #4 were found toward the end of our stay. #3 started out as a fairly large room with a low ceiling, and a canyon carved through the ice on one side of the room. Below that canyon, more cave passage could be made out, but not reached. At least not with the limited amount of vertical gear that we had made the porters drag up the mountains. (We hadn't bothered, because previous expeditions had not found much in terms of vertically developed caves on the glaciers in the Solukhumbu region.) Cave #4 was a few hundred meters long and fairly well decorated with ice formations. By the time we found it, we had run out of time for a proper survey, though.

Pati admiring drapery.

On our last caving day, we returned to cave #1 to help David Breashears of GlacierWorks, who we had run into a few days earlier, make the cave virtually accessible for education purposes. Mainly by Jason pointing out and explaining relevant features of the cave to support still and video photography taken by GlacierWorks.

To sum it all up: We had a good time, got to go play in some beautiful caves, help an education project, and learn some new things about the Ngozumpa Glacier. And since this was a self-financed trip, we also took the liberty to "tourist" around and spend afternoons climbing Gokyo Ri and hiking out to the Fifth Lake for a view of the intersection between the Gyazumba and Ngozumpa Glaciers. A truly beautiful place.

View from Gokyo Ri at sunset: Everest & Co; southern part of the Ngozumpa; Gokyo; and parts of the Third Lake.

p.s.: Don't try this at home. ;-) While some of the dangers of glacier caving are quite obvious (rocks hitting you while you run in or out of the debris-covered entrance), others (such as, false floors, and cracks in the ice that indicate the potential for a collapse) aren't. Jason spent several hours teaching us what to watch out for...


  1. Nice photos! Thanks for the explanation on why the glacier is covered in rocks :-)

  2. Talk about coincidence... I'm sat here trying to design a website for some friends who have been exploring the moulins in the Gorner Glacier in Switzerland, and this pops into my inbox via LinkedIn!

    Once the website is on line I'll ping you again and perhaps link to your article if that is ok? I think my friends are interested in gathering expertise from around the world with regard to exploring moulins and the internal working of glaciers, on the basis that they give clues to climate change.