Phytoplankton produce 50-85% of all the oxygen on Earth, and cyanobacteria did even more before them. Before all this free oxygen could float around in the air, all the metals in the ocean had to be oxidized, which is where the massive banded iron formations come from, and then all the minerals in the crust had to oxidize too. Every layer of Earth’s surface was radically changed by this, taking a billion years and likely prompting the evolution of eukaryotes.
Phytoplankton produce 50-85% of all the oxygen on Earth, and cyanobacteria did even more before them. Before all this free oxygen could float around in the air, all the metals in the ocean had to be oxidized, which is where the massive banded iron formations come from, and then all the minerals in the crust had to oxidize too. Every layer of Earth’s surface was radically changed by this, taking a billion years and likely prompting the evolution of eukaryotes.