How do scientists explain the cause of the Ice Age(s)?

I am not a scientist, but as far as I know there are two necessary requirements for an Ice Age: lower avg temperatures and more precipitation. But the problem is that lower temperatures cause less moisture in the atmosphere and thus less precipitation. I haven't seen a secular explanation for the cause of the Ice Age that addresses both requirements simultaneously.However, if the Biblical Flood happened, and the "fountains of the great deep" (Gen. 7:11) contributed to the waters, then all that warm water or molten rock or whatever was coming out of the "fountains" could have caused warmer oceans and therefore a higher rate of evaporation and more atmospheric moisture.
We also know that there was more volcanic activity during the Ice Age, which is known to cause cooler temperatures. When these two things combined, it could have caused an Ice Age of several hundred years (not 100,000 years).What is the secular explanation for the cause of the Ice Age(s).

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