Gentle Snow

On Enceladus a moon silently orbiting Saturn there is a gentle plume of water vapour pushing out delicate ice crystals on to a slowly forming snow field. The snow is at least 100 meters deep even though it is growing by only 1/1000th of a mm per year. How long has it taken to get that deep? Check my arithmetic, 100 million years. That is a touch longer than the Bible's 6,000 huh?