Glide avalanches:

 

Glide occurs when the entire snowpack slowly slides as a unit on the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow and pose a hazard that is very difficult to forecast. They are often preceded by glide cracks (full depth cracks in the snowpack), though the time between the appearance of a crack and an avalanche can vary between seconds and months. 

Glide avalanches are unlikely to be triggered by a person, and many glide cracks don't result in avalanches.  That said, it's not smart to muck around on or below visible glide cracks.