What causes an Ice Age?
When a significant portion of the Earth's water is trapped on land in continental glaciers, an ice age occurs.
It takes thousands of years for an ice age to start; they don't just appear out of nowhere.
When summertime temperatures in the northern hemisphere fail to rise above freezing for years, an ice age begins.
According to previous cycles, an ice age is probably about to begin on Earth. In fact
At least 6,000 years ago, the conditions were beginning to be favorable for a new ice age.
Ice ages have had a tremendous impact on the evolution of humans.
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