The real questions is not: “Why is there so much carbon dioxide in our atmosphere today?” but “Why is there so little?” Earth’s two sister planets, Mars and Venus, have atmospheres composed almost entirely of carbon dioxide (CO2). And there is every reason to believe our original atmosphere was almost pure carbon dioxide. Where did it go? It went into formations such as those found in Bat’s Head, Dorset, England (see picture). It went down to the bottom of the seas, becoming part of the crust and mantle. Almost all of our original atmosphere has been locked in Earth’s rocks. In short, we are standing on our ancient atmosphere.

Volcanoes release carbon dioxide into the atmosphere. 1

5. Rain contains carbon dioxide, making it slightly acidic 5. Rain contains carbon dioxide, making it slightly acidic. Rock is dissolved or weathered by the acid rain while carbon dioxide is removed from the atmosphere. 5

6 6. Groundwater, rich in CO2 and minerals, can form stalactites (hanging “tight” from the roof) or stalagmites (the mounds on the floor). As the dripping water evaporates, the minerals precipitate.

3b. A calcite crystal forms from a drop of water in an underground cave. This process has locked up some of our ancient atmosphere.

7a 7a. Driven by upwelling molten rock, the ocean floors are separating. Carbon dioxide is released from the hot rocks and lava in this area. Much of this CO2 is dissolved into the ocean water or taken up by life forms…

7b. Marine organisms take calcium and carbon dioxide out of solution to make shells and skeletons. Their remains collect in layers on the ocean floor to form limestone. 7b

( CaCO3 = Calcium carbonate ) 7b Coral Reefs – tie up carbon in CaCO3 ( CaCO3 = Calcium carbonate )

7c Sea Shells – tie up carbon in CaCO3

7d. When sea organisms die, their remains collect in layers on the ocean floor to form limestone and chalk. 7b

Limestone Cliffs - formed from old ocean floor, reefs and sea shells Limestone is made of Calcium carbonate.

9 9. Ocean floors, subducted under continental plates, generate enormous heat which drives volcanoes.

9/1. Carbon is re-released from the crust as volcanoes release carbon dioxide back into the atmosphere 1

Mt. Pinatubo, Phillipines

10. Forests “inhale” CO2 and produce oxygen as a byproduct during the photosynthesis stage of the organic carbon cycle. So, tree store a lot of CO2 that would otherwise be in the atmosphere

Chlorophyll – Green Pigment that makes Photosynthesis possible

7b. “Slash and Burn” fires in the tropical rain forests are doubly bad, because: Burning releases a lot of CO2 into the air.

7b. “Slash and Burn” fires in the tropical rain forests are doubly bad, because: the dead trees are no longer able to “inhale” CO2 during photosynthesis.

Venus-(800oF) - Too Hot! Venus never learned to “inhale” CO2 into its rocks.

Mars (-67oF) - Too Cold 12. Mars never learned to “breathe” CO2 back out of its crust.

Earth - The “Blue” Planet - “Just Right” 13. Earth achieved a balance, taking in just as much CO2 as it releases.