Genesis 7: 11 – 12: In the six hundredth year of Noah’s life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened. And the rain was upon the earth forty days and forty nights.
Job 38: 29 – 30: Out of whose womb came the ice? and the hoary frost of heaven, who hath gendered it? The waters are hid as with a stone, and the face of the deep is frozen.
When the fountains of the great deep were broken up by the tremendous earthquakes at the Flood, it caused super pressurized hot water to be released from inside the earth and gush into the oceans of the antediluvian world, raising the sea level and covering the world’s landmass with water (Genesis 7: 20: Fifteen cubits upward did the waters prevail; and the mountains were covered.).
When the forty-days of cataclysmic convulsions to the planet had expired, the waters that had flooded the earth began to subside, draining off the landmass and forming the oceans we have today. The oceans were warmed-up by this high temperature water being pumped into them and by the lava flows of volcanic activity all over the planet. Being warmer, the water in the oceans evaporated faster than it does today, and great clouds of water vapor formed in the skies, moving over the land.
These clouds carried much more water than the clouds we see today due to the much greater evaporation rate from the warmer oceans. Consequentially, the amount of rain and snowfall in the years following the Flood was far higher, and snow fell over a much larger area, in places that do not have snow today. With all the volcanic activity that occurred at the time of the Flood, huge amounts of ash had been blasted into the atmosphere which in turn blocked a lot of the sun’s warmth from reaching the earth, so places which are warm today were much cooler then.
The volcanic ash and thick clouds in the skies kept the landmass cooler, thus the snow on the ground did not melt during the summer, but instead turned to ice and gradually built-up into thick ice sheets which eventually covered about one-third of the earth’s landmass. After many years the oceans slowly cooled down, and with less evaporation from the cooler oceans, there was less snowfall. The volcanoes around the world also became less active and the ash in the atmosphere gradually cleared away, letting the sun’s warmth through to melt the snow and ice each summer.
Eventually the ice age was over. It had lasted approximately 700 years; five hundred years to build up and two hundred years to melt away. As the waters from the melting ice poured back into the oceans, the sea level began to rise, inundating the formerly exposed land bridges between the continents and other bodies of land which had been used by the animals to move throughout the world after the Flood.