Research evidence supports three major glaciation events in the distant past

Glaciers reached Cape Cod, Mass., in the most recent ice age about 20,000 years ago. But much harsher ice ages hit the Earth in an ancient geological interval known as "the Cryogenian Period" between 750 and 600 million years ago. A team of geologists from China and the United States now report evidence of at least three ice ages during that ancient time.