For many people, the last few days have been unbearably hot. Hopefully, that will change today.
I’ve tried to not talk about the heat, using the theory that if I don’t think about it, it isn’t real. This is similar to the Ravenous Bugblatter Beast of Traal, from The Hitchhiker’s Guide to the Galaxy, “a creature so mind-bogglingly stupid that it thinks that if you can’t see it, it can’t see you. Therefore, the best defense against a Bugblatter Beast is to wrap a towel around your head.”
Thinking like this doesn’t always help, so I also like to think about cold things. There are fewer things colder in the history of the planet than Snowball Earth.
Snowball Earth happened more than once during the Proterozoic Eon. These global ice ages occurred 2220 Ma (million years ago), 710 Ma, and 640 Ma. After the end of the last one, life as we know it evolved and expanded into the diversity we see today.
A global ice age is not great for a planet, although after the weekend I’ve had, I could use some ice. How cold was the planet during a Snowball Earth? The mean temperature could have been -74°F. Because the planet was mostly ice, the sun’s radiation was reflected back to space and did not warm the planet.
There are many theories about what caused Snowball Earth. One popular one is that as the landmasses joined together as one supercontinent at the equator, the tropical environment caused more weathering that reduced greenhouse gases. This caused ice to form on the polar oceans, and the cooled atmosphere increased the size of the ice sheets, eventually reaching the supercontinent. Once half the planet was covered in ice, a tipping point happened, and a Snowball Earth was born.
Lucky for the planet and its inhabitants, plate tectonics continued even with a covering of ice. Eventually, the supercontinent cracked apart, and volcanoes erupted lava and gasses. This increased the amount of sun absorbed by the planet, and the ice melted.
This cycle of heating and cooling happened at least three times during early Earth. One reason why we have a steady, livable temperature today is that the land is scattered around the earth and not bound together as a supercontinent. However, another supercontinent will happen, and depending on many factors, another snowball Earth could be in the far future.
Until then I hope the weathermen are right and cooler weather is here.