I think it is funny, that Geologists use fossils as the markers for geological era.
I mean, you could expect guys that deal with rocks and continents to rely on something… less fragile. It seems, however, that this is the best they’ve got: they even like to date rocks by the types of fossils you find in them; other methods (e.g., radioactivity, location relative to other rocks, etc.) are also used - but life remains are much more central than what you’d imagine. Anyhow, a few days ago a couple of friends asked me a bit about it, which gives a good opportunity to dig a bit into the largest timescale on Earth: the geological timescale - and its close connection to the evolution of life, and - funny enough - is divided by mass extinctions, some of them more famous then others. Following is a short summary of the geological epochs: it may be a bit tedious, but I think it is a good general knowledge, and it can do the job in putting us in a proper frame.
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