Belays on snow are usually fairly low down the list of preferences but on occasions they may be the only ones available. The problem with snow anchors is that it can be difficult to assess their strength, which is dependent on the nature of the snow cover, and they can only be as secure as the snow in which they are placed. If the slope is unsafe then any number of snow anchors will still not make you secure. In hard snow they may be nearly as good as rock anchors but at other times they may be no more than psychological security.
Sometimes snow belays may be no more than psychological security
The actual anchor used will depend on conditions and the equipment you are carrying but all will be better when the snow is hard and consolidated. When placing them, the more information you have about the snow-cover the better. Do this by digging a quick pit to show the various layers in the snow and so help you decide which anchor will be most suitable and perhaps the best depth at which to place it. Even pushing your axe shaft down into the slope can reveal the different resistances of the layers in the snow.
Snow anchors are strongest when they are loaded directly down the fall line and they should be placed so any force pulls them into the slope rather than out from it. Consider the stance as an integral part of the whole belay system too. Since there is usually some element of doubt about a snow anchor it is important to have a stance which is shaped so that if there is a force on the belayer, he or she will be able to take some of the load on their body and so reduce the force going on to the anchor. This is a sitting position. Cut the stance horizontally across the fall line and cut it so that both the steps and the seat angle back into the slope.
In this case the belayer will be pulled down into the stance and not off it. A stance like this can be further improved by extending it into a saddle shape behind which the belayer can brace himself. If you use a standing stance, the ledge should again angle back into the slope. Any stance should be far enough below the anchor to ensure that the pull comes down, and not out.
There are several types of snow anchor, each of which have their own advantages and disadvantages.
This spade-shaped metal plate gives the best anchor in the widest range of snow conditions although, like all snow anchors, it is strongest in hard snow conditions. You must place a deadman correctly - and the softer the snow the more important this becomes. Place the plate at an angle of 40 to the slope. To find this angle, use the right angle on the plate to put your axe at 90° to the snow surface. Take the plate and bisect this angle on the uphill side and push it back another 5°.
This is best done by looking directly along the plate so that the angle can be judged more accurately. With the plate pushed into the snow and acting as a guide, dig a slot across the slope at right angles to the fall line and at the 40° already estimated. The depth of this horizontal slot depends on the hardness of the snow but a fair guide is dig as deep as is comfortable; this may be 25cms in hard snow to 50cms or more in soft snow. Now dig a slot for the wire running down the fall line. Keep this as narrow as possible, using the pick or the shaft and make it at least as long as the wire itself. Make vertical slot deepest at the top and tapering up to the surface at the lower end. When doing all this digging, stand to the side and try to disturb the snow in front of the plate as little as possible, particularly if the snow is soft.
Now place the plate in the horizontal slot, holding it against the front face and hammer it into the snow until the top of the plate is at the bottom of the slot. Keep the wire in tension while hammering so that it cuts down with the plate. By keeping it against the front face which has been cut at 40° to the slope, you know that when it disappears into the snow it is going in at the correct angle. When in place, the internal angle between the plate and the wire should be 50°, so that when the wire is loaded the plate will cut down into the slope and become stronger. If it is placed at too shallow an angle, the plate can cut down through the snow too easily and will eventually pull out where there is a weakness - which will be at the stance if not before. If it is too upright it can pull up and out when loaded. This can also happen if there is a bend in the wire.
The deadman works best in hard snow so it is best to place it in the hardest layers even if this means clearing off surface layers. If the plate pulls down and hits a hard or icy layer it will probably not penetrate this harder surface but will change angle and skid down on top of it. Very occasionally the opposite may apply when the plate is put in close to the surface to make use of hard snow lying on softer layers.
When the deadman is in place, finally bed it in by using your axe as a lever through the karabiner on the bottom wire. You can then clip your rope through this karabiner and descend a sufficient distance below the plate, cut a stance and tie into the anchor. The stance must be directly downhill from the plate to ensure that any load on it is directly down the fall line. The deadman is always placed at the same angle to the slope no matter what the slope angle is. If using one on flat ground - such as at the top of a climb - it should still be placed in the same manner. Deadmen can be used as running belays as well as main anchors but they are inconvenient to carry, although in some situations they can be the only protection available.
Buried axe anchor
To make a buried axe anchor, first cut an adze width slot at right angles to the fall line and a little longer than the length of your axe. Keep the slot is vertical or angle it back slightly into the slope, but it must not slant outwards. Cut it as deep as possible and make use of any hard layers in the snow. Then cut another slot down the fall line and joining the horizontal slot about one third of the way along. Cut this vertical slot as narrow as possible, sloping from the bottom of the horizontal slot to the surface to its lower end.
Attach a sling to the axe shaft with a clove hitch (which will tighten up when loaded). Put the sling on about half way along in terms of surface area; this is normally about the point of balance of the axe. Then place the axe in the horizontal slot with the pick down and the shaft hard against the front face of the slot (Fig 7). This anchor will not cut down through the snow if loaded but relies on resistance for its strength. One problem is the axe pivoting and pulling through the snow and this is why it is important to use a clove hitch which will grip the shaft and not slide along it. Ensuring that the axe is hard against the front face also reduces the chance of pivoting and so pulling out. If another axe or ice hammer is available, use it to reinforce the anchor by pushing it vertically into the snow in front of the horizontal axe but running down through the sling. Always remember to cut your stance before burying the axe!
T axe anchor
This is similar to the reinforced buried axe but the vertical axe, which has a sling clove hitched around the shaft just below the head, is placed behind the horizontal axe. Both the horizontal and the vertical slots can be shallower than with the buried axe because this anchor works on leverage rather than on straight resistance. However, it does require more experience to judge its strength and suitability but it can be the best type of anchor in snow cover which contains narrow layers of snow or ice which can be exploited by the depth of the vertical axe. If speed is important it can also be quicker to set up if speed. Instead of a horizontal axe you can use anything such as walking poles, hammer, tent poles or even a suitable rock. But as always, you must cut a good stance below and arrange the pull so that it comes down along the slope.
A snow bollard is a simple and effective anchor, especially in hard snow. First mark a horseshoe shape on the snow, its size will depend on the hardness of the snow but it should not be less than one metre across. Cut the bollard so that the slots are deepest at the back with a retaining lip at the top to ensure the rope stays in place. In some types of snow you can increase the bollard's strength making it bigger but the usual reason for failure is the rope cutting through the snow. In soft conditions you can guard against this to some extent by padding the rope with spare clothing or rucksacks or by pushing axes into the widest point where cutting is liable to be greatest. (Fig 9). When digging a bollard try not to disturb the snow in front of it and arrange the rope so that it is in the hardest layer of snow. Bollards are particularly useful in shallow hard snow which is not deep enough to take one of the other types of anchor and also in retreat situations when they can be used to abseil from without leaving any gear behind.
You can use ice for anchors, and these are usually stronger and more reliable than those on snow. It may also be possible to increase the number of ice anchors to give an acceptable belay in a way that is not feasible on snow.
Ice pegs, usually screws, are the normal ice anchor and you'll need at least two. Ice pegs need to be placed 10° back (uphill) from right angles to the slope and inserted fully so that the eye points downhill and is flush with the ice. In very good ice however, modern screws can be place at 10° down from the vertical for maximum strength when the size of the screw thread is important. However, when placing a screw in this manner the quality of the ice is crucial.
Tubular screws are generally the best as they are strong and less likely to crack the ice than drive-in pegs which are seldom used now. The longer the screw and the larger the threads the stronger it should be, but this will always depend on the quality of the ice. Modern screws are easy to place simply by screwing them into the ice. Older types of ice screws, which have fewer teeth and thicker walls, may be more difficult to place. You may need to first chip a small hole in the ice and then give the screw a few taps with the hammer to get the threads to bite initially. If it becomes too stiff to turn by hand use your axe for leverage.
Some screws come with an extension handle to make placing them more efficient. Be careful to stop if you feel any sudden resistance as this probably means that the screw has reached rock and if you continue turning the teeth will become bent and the cutting edge damaged making the screw unusable. If the resistance suddenly eases this usually indicates a weakness in the ice, such as a layer of snow or air which will make the screw much less secure. Drive-in pegs are simply hammered in at the correct angle.
To remove ice pegs simply unscrew them. Tubular drive-in pegs can be hammed in a bit more to break their grip on the ice before unscrewing. Again, you can use your axe can be used as a lever for this. You'll not be able to re-use tubular ice pegs until you remove the core of ice in the centre - just push it out. Some screw have a tapered interior to make this easier but it is not always possible especially in very cold conditions. Alternatively, you can melt the ice by putting the screw close to your body, or blowing down it and tapping to loosen the ice.
When you use two pegs they should be placed in separate bosses of ice to spread the load. This may not always be possible, so make sure that they are about one metre apart and offset at about 45° to each other. If you place pegs placed at the same level horizontally or vertically one above they are more likely to crack the ice. You can often supplement ice pegs by axe and hammer picks driven in as far as possible and tied into the system. On their own however, picks are not secure enough to form a belay anchor.
Another possibility with ice pegs is to use a drive-in, usually a Wart-hog in frozen turf. Though more commonly used as runners they can form part of a belay system if nothing else is available, they can be quite good providing everything is well frozen.
Ice screw threads
Using one ice screw it is possible to make an ice screw thread (or Abalakov thread). These can be very strong and secure and are particularly useful in an abseil situation or when only one screw is available. First place the screw in the ice at 10° beyond right angles but angling in at about 45° to 60° to the side. Then remove it and replaced it at a similar angle from the other side, so that the two holes meet forming a V-shaped tunnel. The wider the screw you use, the easier it is to get the two holes to meet and to thread. Then thread a piece of tape or rope through this and tie it in a loop to form an anchor. Use a piece of wire to make this easier.
This is a simple, strong and effective anchor which can be cut in quite thin ice but one which can take some time to create unless you are well practised. It's best to make the horseshoe shaped bollard where there is a change angle of the ice to reduce cutting. Do most of the initial cutting with the adze and finish it with the pick. Take care in the final stages not to hit the bollard itself - it is better to cut out the ice behind the bollard. Do the final shaping by scraping with the teeth on the underside of your pick. This is particularly true when creating the lip to keep the sling or rope in place. Make sure that the load is kept downwards as much as possible, as this is stronger and with less chance of the sling coming off. Sometimes you will find that the ice itself forms natural features (such as an icicle that grows into a pillar) and these can be threaded. It may also be possible to cut through a curtain of ice to form a thread. In these situations arrange the rope or sling so that the pull is forced downwards as much as possible. However, this type of anchor is likely to be less secure and should only be used in an emergency or linked in with other anchors to form an acceptable system.