The most recent (2013) edition of Climbing Anchors, by Long and Gaines, makes some interesting statements in the preface about catastrophic failures of anchors. Long first says that: when belay anchors fail, it's usually in cases where the gear was placed in a horizontal crack, and the anchor was subjected to a shock load sideways to the intended direction of pull. He attributes this to anecdotal reports. He also says the following, which I find very surprising.

Because statistically, the majority of climbing accidents occur from leader falls, we'd expect catastrophic anchor failure to result from a leader taking the dreaded Factor 2 ripper right onto the anchor. Not so. Most of these failures involved a leader belaying a second up on a toprope.

So from this information, it sounds like these failures often happen the first time the anchor is ever loaded, i.e., it was such a poor anchor that it wouldn't hold even a top-rope fall.

Is it possible to find systematic statistics anywhere on the types of anchor failures (top-roping, leading, ...) and how survivable they were? In the case of the leader belaying the follower, it seems like the failure might actually be survivable in many cases, since there might still be a lot of gear down below that hadn't yet been cleaned. (But the belayer had better maintain a serious death-grip on the rope!) Even if, as Long says, few failures are from factor-2 falls, those are probably the ones that would not be survivable at all, since there is no other gear present.

I'm also having a hard time reconciling the statements that:

  1. "anchor failures are usually from a load "sideways to the intended direction of pull,"
  2. they usually happen while the leader is belaying the follower.

When the leader is building the anchor, his rope is trailing right back toward his last piece of pro, so it should be dead obvious what the direction of pull is going to be when he catches a fall by the follower. The exception would be, I guess, when there is a traverse from the last piece to the belay station, and the follower takes a fall after cleaning that final piece (and in this case, the anchor failure is probably not going to be survivable).

I would also be interested in statistics about how many accidents are caused by anchor failures while climbing, as opposed to rappelling. The latter seems more common, which probably isn't so surprising, since people usually try to make their belay anchors really bombproof.

  • As I read it he's saying that the majority of accidents are from incorrectly set up belays. So the leader has lead the climb, set up a belay for his second to follow. At some point the leaders belay has been loaded (second falls maybe) the gear isn't high enough so is loaded horizontally and pops out. Leader falls. I'm not 100% clear what your question is though. Can you clarify?
    – user2766
    Oct 20, 2014 at 12:21
  • Do you have a link to the original article?
    – user2766
    Oct 20, 2014 at 12:52
  • I'd suggest emailing John Long to ask; IIRC anchor failures are quite rare, although the 2012 ANAM intro suggests anchor failure accounts for 26% of rappel accidents. (It's also possible the DAV has good numbers on this, if any Germans are reading...)
    – requiem
    Oct 20, 2014 at 15:28
  • It's very unlikely that a belay failure would be survivable, once the rope has held an initial fall it takes time to become elastic again. Any load after that is essentially static and climbing gear is simply not manufactured to deal with the forces generated by a static rope when falling, google zipper effect. Mar 18, 2015 at 16:07
  • @FredtheMagicWonderDog: I do not find anything by googling about zipper effect, can you refer my to a source. That would be the first time I hear about it while it has pretty serious implications.
    – imsodin
    Mar 24, 2015 at 21:25

2 Answers 2


Personally, I can easily see how this unintended loading can happen.

Second gets to a tricky part, asks leader for beta, leader moves over to get a better view of second.

This question is an example of one of the really hard problems in climbing. It's almost impossible to get feedback about how well you are building your anchors. You just don't get many chances to be wrong.

99% of the time any protection you place simply won't be tested in any way. Most of the time it simply doesn't matter if you build a crap anchor or a bomber one. If nobody falls or the belayer has a good enough position to hold the fall with body weight, the anchor never gets stressed. It's next to impossible to know if you are good or just lucky.

You can develop or follow really bad practices for a very long time and not suffer any consquences. The America Death Triangle is a classic example. In the 70's when I was learning to climb, that was standard practice in the USA. Everybody I climbed with used it, so I used it too.

Ideally, you'd like to spend time building anchors and throwing dummies off cliffs, but that's expensive in ropes and time.

One way you can get better at building anchors is aid climbing, but that pretty old school these days.

  • Every belay is different, some, you know (think?) you have bomb proof anchors, others, you know(think?) are 'less than ideal' but its the best you can do. I wonder what the correlation between what the belayer thought, and reality, has been studied (although the probable outcome of a belay failure precludes a rigorous study) .
    – user5330
    Mar 18, 2015 at 20:22
  • 3
    All the psychology in this situation is bad. Humans have a bias to attribute to skill any positive outcome, regardless of how much random factors determine the outcome. Mar 20, 2015 at 14:45
  • You can test your gear placement practice on bolted routes. Of course it doesn’t tell you if your placement is perfect, but at least you can test some longer lead climbing falls on equipment without any danger.
    – Michael
    Feb 17, 2020 at 11:59

There are no statistics because no-one really keeps statistics about anchor types in accidents. Possibly also because anchor failures are extremely rare.

However, individual case studies on specific anchor failures do exist. For example, http://publications.americanalpineclub.org/articles/13201215224/Rappel-Anchor-Failure-inadequate-Anchor-and-Backup

It is also largely impossible to examine, objectively, the "bombproofness" of an anchor which is highly subjective. The best we can do (objectively)

  1. Examine placements
  2. Sanity Check rigging (no force multipliers)
  3. Check for objective hazards (loose rock, avalanche, etc)

The rest is a matter of personal preference/belief and to a large degree - luck. We limit our exposure and rarely do we maximally load our anchors.

We have good objective knowledge on which anchors do not work, but there is much less clear information on how generally applicable anchors can survive extremes, and much debate can be had about the best anchor to use and which specific corner case allows it to shine, but in the end the only answer is

It Depends, but KISS

Rarely do we build "universal anchors" and as an example most climbers will rappel off of something much less "bombproof" than they would belay from (application specific subjectivitiy). If you anticipate side-loads then you must build to withstand side-loads, but agonizing over side-loads in every situation is somewhat counterproductive.

However, Statistics do dictate that minimizing exposure increases your odds of survival the most and simplicity reduces chance of error so most effective use of your time is to develop reliable systems that you can build fast and in the most situations and can do fatigued and on 72 hours with no sleep

The best we can get are accident publications. In the US and Canada this is "Accidents in North American Mountaineering/Climbing" published by the American Alpine Club.

The best conclusion to draw from the published statistics here is that the vast majority of accidents involve a leader fall with inadequate protection and generally as often as not involve no belay at all. Rappel errors account for some amount of accidents, but this category includes rappel errors of all kinds.

What we can say is that pulled gear, or gear failure (the rarest of events) is only a contributory cause in approximately 400 out of 8000 accidents in North America between 1951 and 2017

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