Snowball Earth
We know that the earth was snow covered, even at/very close to the equator, repeatedly. There’s even a very evocative term for it: “snowball earth”. The most recent series of snowball earths, comprising of four great ice ages, started about 750 million years back, writes Nick Lane in Oxygen . What may have set off that chain makes for fascinating reading. The most plausible explanation is based on those tectonic plates moving around. If you didn’t know already, the movement of those tectonic plates is what causes earthquakes, created the Himalayas, and why the coasts of Africa and South America seem like jig saw puzzle pieces that fit so well. But what’s that got to do with ice ages? Lane explains. When rock is exposed to carbon dioxide in the air, it is eroded (since CO2 is weakly acidic). In the process, carbonates are formed and the CO2 level in the air reduces correspondingly. Now imagine an ice age where ice covers the land. In this scenario, the rocks and C...