for thousands of millions of years the earth has been changing, with cycles­ and one-off events such as an asteroid impact, super-volcano or a supernova explosion.
for thousands of millions of years the earth has been changing, with cycles­ and one-off events such as an asteroid impact, super-volcano or a supernova explosion.
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high-latitude regions have since undergone repeated cycles of glaciation and thaw, repeating about every 40,000–100,000 years.