chalk

A great chapter in the history of the world is written in chalk.
- Thomas Huxley, 1868

A piece of chalk is an incredible thing. Under a microscope it's a series of small white globes that look like a snowball made of brittle trivets. The trivets are part of ancient skeletons that once belonged to tiny creatures living and floating in the sea that captured carbon and sunshine, then died and sank to the ocean floor. Over millions of years so many have died and sank and laid one on top another that, along with the weight of water above them, they've formed a white blanket of rock. Hence the White Cliffs of Dover.