snow keeps skiers alive
The main factor in surviving a 100 foot fall is how well the material your landing on slows down your acceleration due to gravity.
What would you rather land on... concrete or a big blanket of white puffy snow?
The Physical aspect of landing on snow has to deal with the materials impulse, how well it can increase your collision time so the overall force is minimized.
IMPULSE = FORCE * TIME
Impulse is equal to the product of a force's magnitude multiplied by the time over which the force acts. Thus the greater the force is, the greater the time it acts is, or both together, the greater is the impulse. The smaller the impulse the less force you will endure.