Rockfall  Fatality in the Ramsay

Rockfall is an increasing hazard in the Central Southern Alps due to glacial recession. Learn from the sad events of November 9, 2002, when a young climber died on the shores of the Ramsay Glacier terminal lake.

Area: Ramsay Glacier terminal lake, central Southern Alps, November 9, 2002

Activity: Mountaineering approach

Deceased: 26 year old male

Survived: 27 year old male

Summary:

After two nights camping in heavy rain on the Ramsay Glacier, two mountaineers abandoned camp and headed down glacier reaching the terminal face in the late afternoon.


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They traversed along the edge of the terminal lake at the foot of steep scree and boulder slopes. This area of obvious but unavoidable danger is the only exit route from the Ramsay Glacier in bad weather. The pair heard a loud bang like an explosion. The man in front yelled a warning as a shower of rock came down. He was knocked into the lake and sustained serious injuries which prevented him from swimming.

The survivor succeeded, on a second attempt, to swim out and float him back to shore. He set up a camp and tried to keep his friend warm and alive, but he died at about 7:30 pm. Having secured the body the survivor went to Reischek Hut to raise the alarm, but the radio did not work. He got a message out the next afternoon. In this interview he tells about his part in the incident, how it affected him and what he learned.

JM: What were your priorities when you saw the accident?

The rock-fall happened so fast that all I had time to do was drop and crouch under my pack and hope that nothing big would hit me. JM: What were your priorities during the rescue? My initial priority was to get him out of the lake as I knew he would not last long in the very cold water. Once out of the lake I knew he was in serious trouble and would need medical help, so I would need to leave him somewhere for at least a day. I had to get him off the scree slopes because I was worried about further rock fall. I planned to erect our tent on a beach on the lake edge so I could put him in a sleeping bag out of the wind and rain.

JM: How did you ensure your safety?

In getting him out of the lake we had drifted away from the area of the rock-fall, and the slopes above were less steep and looked relatively stable. However, the weather was still bad and there was no reason why further rockfall couldn’t happen. I put my helmet on. I was very cold from being in the lake but felt like I was running on adrenaline as I tried to drag him to the lake edge and relative safety.

JM: Did you panic, or did you go into “auto mode”?

I felt like I went straight into auto mode. There was a bit of panic when I first dived in the lake with the shock of the cold causing me to lose feeling. However, I was straight back in auto mode again as I dived back in the second time, knowing I had to get him out of the lake. Once I had him ashore, all I was thinking about was getting him into a tent beyond the scree slope so I could head out for help.

JM: Do you have any advice for others caught in a tragedy like this?

Trust your instincts. Everything happened so fast. It was obvious that I had to get him to safety and out of the cold. Running on auto was the only thing to do. JM: What have you learned? I have bought a personal locator beacon and take it on tramping and climbing trips. I’m wary about the sort of terrain I visit on tramping trips and would look to avoid routes which traverse under steep scree slopes around glacial lakes. I’d also think twice about heading into the mountains on a serious trip with only two people in a party. A four person party provides a better margin of safety but obviously it is not always practical to head away with a group of this size.

JM: What helped you cope afterwards?

The support of friends and family, and spending time with my friend’s parents. I visit them whenever I go south for tramping and climbing, and we’ve become good friends.

 

The Ramsay Glacier rock-fall

Mauri McSaveney, Tim Davies and Gordon Ashby examine the fatal rock-fall of 9 November 2002

As part of the GeoNet natural geological hazards monitoring contract between the Institute of Geological & Nuclear Sciences (now GNS Science) and the Earthquake Commission, a response team investigates incidents of land instability involving loss of life. We made this investigation under this contract.

We flew in by helicopter in fine weather on 18 November 2002 and spent about an hour at the site, inspecting the area from the air and from safe ground adjacent to the fatal rock-fall. Although no rocks fell on the scree during our visit, we judged it unstable and liable to further collapse without warning. We heard many rocks falling in nearby parts of the valley.

When the Ramsay Glacier was named more than 140 years ago it contributed water directly to the Rakaia River. However, glacial recession in the last 100 years has developed a short Ramsay branch of the Rakaia River and a lake between it and the Ramsay Glacier. The un-named lake is now about 700 metres longer than shown on Infomap J35.

The rock-fall hazard to the Ramsay Glacier route is a result of glacial recession since 1986, making necessary a traverse of the foot of a steep wall of moraine below Mt Ramsay. Further recession may expose a precipitous bedrock slope at the lake shore rendering the route impassable.

The moraine wall exposed by retreat of the ice is of weakly consolidated gravel standing at up to 50° to 60° in its upper and middle
slopes. Many of its boulders are more than a metre across, and some exceed ten metres. The lower part is mantled by coalescing screes formed by debris from many rock-falls in the absence of the glacier that previously supported the moraine. The screes lie at 25° to 35°, at the margin of stability for such materials, and form the lake shore.

At the southern end of the rock-fall screes is the former junction of Ramsay and St James Glaciers. Here the moraine wall merges with that of the St James Glacier and reaches a height of about 270 m above the lake. Its upper part stands at 40 to 45°. The rock-fall scree below it is surfaced mostly by huge to enormous boulders, the larger of which lie at its base and in the lake. The accident occurred at the southern foot of this scree.

The logical route to Ramsay Glacier traverses among the boulders at the foot of the slope. It is not a discernible path because the scree is too active to retain evidence of human passage for long.

The rock-fall site is about 5 km from the Main Divide, within the zone of spill-over of westerly rain. Rain and strong wind from a strong south-west airflow covering much of New Zealand affected the Rakaia valley for some days up to and including 9 November 2002, probably contributing to the instability of the slope by wetting and weakening the moraine.

Aerial view (to north) of Ramsay Glacier. Approximate extent of lake in November 2002 is shown by dotted line. Arrows mark the location of the fatal debris fall. Photo (1995): Trevor Chinn

We estimate the collapse to have been 5,000–10,000 cubic metres in volume. Only the biggest boulders (up to several metres across) and fragments from high velocity collisions reached the bottom of the slope, while finer material was trapped between boulders further up. Some debris went out of sight in the lake.

The fallen boulders are scratched, gouged and freshly fractured from high-energy impacts. Many skipped and jumped, spraying the slope and lake with “shrapnel.” Our calculation of ballistic trajectories indicates a minimum speed of 42m/s (150 km/hr).

The two mountaineers had already traversed the lake shore without incident an hour or so earlier, and had almost completed their return traverse before the tragedy struck. If one or two rocks had fallen they might have dodged them or taken shelter behind other boulders, but this was impossible in such a large collapse. When the pair saw rocks falling more than 200 metres above, they had only about ten seconds to get out of the way. With boulders reaching the base of the scree averaging about one cubic metre (2.7 tonnes), the victim was possibly hit by the equivalent of a small car travelling at 150 km/h.

Fatalities in falls of small numbers of rocks are not rare in the Southern Alps; but this one is unusual in that it occurred in such a large rock-fall. No previous rock-fall fatalities have occurred around the lake. Few people visit the area, and no significant rock-fall hazard existed until about 20 years ago. Now, however, the rock-fall danger is moderate to high along some 700 metres (increasing as the lake grows) of the route. The fatality occurred at the southern end of the danger zone, where the moraine wall is highest and least stable.

Any route on the opposite (east) side of the lake would also be dangerous. We heard several small rock-falls there during our visit.

Reference: McSaveney, M. J., Davies, T. R. & Ashby, G. L. 2003. The fatal Ramsay Glacier rockfall of 9 November 2002. Institute of Geological & Nuclear Sciences science report 2003/2.

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