Carbon isotopes are carbon-12, carbon-13, and carbon-14. Photosynthetic plants use more carbon-12 than carbon-13, so abundant plants lower carbon-12 ratio {isotope ratio, carbon} {carbon isotope ratio} in air. Air trapped in ancient rocks and ice can show relative amounts of photosynthetic plant life at past times.
Physical Sciences>Earth Science>Planet>Temperature History
5-Earth Science-Planet-Temperature History
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Date Modified: 2022.0224