BLAG model

Recently, Ishikawa (1996), and Kashiwagi et al. (2000) calculated CO2 change in atmosphere during the last 30 Ma and the last 60 Ma respectively, mainly based on the method developed by Berner et al. (BLAG model) (1983), Bemer (GEOCARB model) (1994), and Tajika (1998) taking into account hydrothermal CO2 flux from back arc basins and island arcs which were not considered in previous studies. 

Fig. 4.10. Atmo.spheric CO2 variation estimated by modified BLAG model including CO2 flux related to mantle plume activity (Ishikawa, 1996). t c02 = 202/ 002 - prescut-day PcOi)-...

BLAG model (silicate-carbonate model) concerning long-term carbon cycle (Berner et al. 1983) is shown in Fig. 5.3. Basic reactions for BLAG model include reactions between CO2 and Ca- and Mg-minerals (calcite, dolomite, Ca-silicate, Mg-sUicate). 

Giving the changes in seafloor spreading rate and continental area with time, amount of atmospheric CO2 during the last one hundred million years compared with that of present-day atmospheric CO2 was calculated by Berner et al. (1983) (Fig. 5.4) based on silicate-carbonate geochemical cycle model (BLAG model). 

Fig. 5.4 Plots of worldwide mean annual atmospheric surface temperature versus time, based on BLAG model, compared with temperatures estimated from paleobotanical study and 5 0 of planktonic carbonate (35 °N)...

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