Changes between Version 3 and Version 4 of Talks/Fall2006/Colloquium/061101


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Timestamp:
09/20/06 14:12:29 (19 years ago)
Author:
caleb@…
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  • Talks/Fall2006/Colloquium/061101

    v3 v4  
    77with atmospheric concentrations exceeding 1000 ppmv. CH4 is mostly biological in origin; hence, life may have
    88played a direct role in controlling climate on the early Earth. The rise of O2 at ~2.3 Ga, now conclusively established
    9  by studies of mass independent fractionation (MIF) in S isotopes from ancient rocks, caused a marked decrease in
     9by studies of mass independent fractionation (MIF) in S isotopes from ancient rocks, caused a marked decrease in
    1010methane, thereby triggering the Paleoproterozoic glaciations. An earlier, less well documented glaciation at 2.8-2.9 Ga
    1111corresponds to a second anomaly in the MIF record and may also have been triggered by biological innovations.