Before you pitch your tarp or tent for the night or before you build your quinzee, you want to let the snow firm up or sinter. Sintering of snow is when snow crystals lose their points due to molecular motion, wind, and direct pressure.
Initially, snow falls as individual flakes or snow crystals, but pointy crystals and sharp angles are not as thermodynamically stable as more rounded crystals.
In nature, crystals lose their points due to molecular motion, wind, and direct pressure. Physically breaking the snow crystals, for instance stomping on them or disturbing them with a shovel, will produce the same effect. The crystal arms are broken and then rounded grains fuse by freezing into larger crystals in a process called sintering. Snow crystals resulting from destructive metamorphism compact easily and can become very hard and dense.
Rounding and sintering stabilize the new snow and, along with gravity, cause it to settle. Thus, there is a net loss of height- which causes settlement.