The cycle of life-giving elements;

UNTIL THE RISE OF GREEN PLANTS THAT USE SUNLIGHT AND CARBON TO MAKE CARBOHYDRATES. EARTH'S PRIMITIVE ATMOSPHERE WAS FILLED WITH CARBON DIOXIDE; CO2 LEVELS DROPPED AS HYDROCARBONS IN PLANT MATTER FELL AND BECAME BURIED SEDIMENT. VAST AMOUNTS OF OXYGEN, RELEASED AS A WASTE PRODUCT BY PLANTS, WERE IDEAL FOR MORE COMPLEX LIFE FORMS; WHICH IS FIXED BY HUMANS USING OIL, THE REAL GREEN ENERGY SOURCE. BUT BILLIONS OF TONS OF CARBON WERE BURIED UNDERGROUND, OUT OF LIFE'S REACH