Get Outdoors - Snow Climbing: Roped Climbing: Snow Anchors

Anchors are needed in snow for the same reasons they are needed on rock. The equipment is different but the purposes are the same: to anchor belays and rappels and to provide intermediate points of protection.Unlike rock anchors, snow anchors are not easy to inspect nor predictable in performance. They vary widely in strength depending on snow conditions and placement, and their strength changes during the day with changes in the snow. The medium of snow is more variable than rock and requires placement of different types of anchors depending on conditions. This uncertainty makes it even more imperative than on rock to check and recheck any belay or rappel anchor. Snow anchors can also require a lot of time to put in place.

Snow anchors include deadman anchors (such as snow flukes), pickets, and bollards.

Deadman Anchor: Any object you bury in the snow as a point of attachment for the rope. Flukes are most reliable but also more difficult to place in the hard homogeneous snow of summer. They are generally used in a softer but dense pack, snow that is moist and heavy. They are least reliable under typical winter conditions, with snow layers of varying density where they may deflect off harder layers. Neither do they do well in dry, unconsolidated snow.

The most common is the snow fluke, a specially shaped aluminum plate with a metal cable attached.
Ice axes, ice tools, and snow pickets can serve as deadman anchors.
In theory, the fluke serves as a dynamic anchor, burrowing deeper into the snow when it takes a load, such as the weight of a climber on rappel. In practice, it may behave in more complicated ways, even coming out if it is tipped too far forward or backward or if the load is to the side rather than straight out.

Picket:: A stake driven into the snow as an anchor. Pickets work well in snow too firm for flukes but too soft for ice screws. As with flukes, angle them back from the direction of pull. Attach a carabiner or runner to the picket at the snowline-not higher on the picket, or a pull may lever it out. You can drive a picket into the snow with a rock or the side of an ice ax, but a North Wall hammer or other ice hammer works best and reduces the chance of equipment damage.

Aluminum pickets are available in lengths from 18-36? and are found in different styles, including round or oval tubes and angled or T-section stakes.
An ice ax or ice tool can serve as a makeshift picket.

Bollard: A mound of snow that serves as an anchor when rope or webbing is positioned around it. Snow bollards provide highly reliable anchors for belaying or rappelling in hard snow and are possibly the most reliable in all snow conditions. There is a significant trade-off, however. It takes a long time to build one.

Multiple Anchors: As with questionable anchors in rock, multiple anchors are safest because of the inherent weakness and unpredictability of snow anchors.

2 anchors can be chained sequentially so that the first takes the hit but has a backup to absorb any remaining force.
Or they can be connected in a way that will permit them to share any load.
In general, place multiple snow anchors one behind the other to reduce the angle of pull and the potential load on the surviving anchor if the other one fails. Keep the anchors several feet apart so they don't end up sharing any localized weakness in the snow.