40 Billion Tons of Living Organisms Thousands of Years Old

This is mindblowing. The 5km deep subterranean microbiome has microbes that  came into being diring the time of the Pharos in Ancient Egypt. They eat mostly rocks and free electrons. "If you could cut the end off of an electrical cord, they could breathe it like a snorkel!"

The takeaway is that billions of tons of CO2 is continuously being released from subduction zones, but is consumed by chemolithoautotrophes before it reaches the surface of the earth.