https://github.com/davepinch/pinchy.cc/blob/master/content/streams/i-am-having-trouble-getting-started/5/expression-is-training-the-brain.md
In the Cambrian period of the Paleozoic Era, between 530 and 470 million years ago, the region was covered by a shallow sea which deposited sandstone and siltstone atop the basalt.