There has been much discussion of the possibilities, composition, and maintenance of a pre-Flood canopy surrounding the earth. Venus space probes have shown a canopy to be possible; for Venus has one. This paper discusses the idea that not only was the canopy possible but that it was a necessity. It was necessary before the Flood to produce the climatic conditions the Bible describes for that time. When that canopy was emptied its water became the erosional force that produced the sediments that formed the sedimentary rock. A restored canopy was necessary after the Flood to produce the climatic conditions that made Oregon’s weather tropical and that allowed mammoths to live at the Arctic Circle. When that canopy was emptied it produced the ice age and froze and preserved the mammoths.