Carbon Cycle in Geologic Time
One of the most beautiful systems produced by nature is the carbon cycle. It is a remarkable system that mitigates the extremes and deficiencies of the Earth's environmental expressions. We are investigating the carbon cycle of the ancient Earth.
Panel A (before the end-Permian mass extinction): The supply and consumption of carbon are balanced in the Earth's surface environment (atmosphere and oceans).
Panel B (end-Permian mass extinction-Early Triassic): Carbon supply exceeds carbon consumption in the Earth's surface environment. Magma from large-scale volcanic activity penetrates and burns through strata where fossil fuels exist, supplying large amounts of carbon to the atmosphere and oceans (*2).
*1: Carbon circulates in the atmosphere and oceans. CO2 degassing by igneous activity and CO2 release and HCO3- dissolution by weathering (organic matter and rocks). The carbon released and dissolved by igneous activity and weathering is fixed by photosynthesis and calcifying organisms (corals, shells, foraminifera, etc.) and is removed by burial under the seafloor. Submerged organic and inorganic carbon is heated and decomposed by subduction of oceanic plates under the continental crust due to plate tectonics, and is released back into the atmosphere and ocean through igneous activity.
*2: The timing of combustion could be inferred from records of organic matter originating from high-temperature combustion (coronene).
Two of the last five mass extinctions, unluckily, were possibly caused by the combustion of abundant fossil fuels in the strata.
Response of the carbon cycle to different rates of fossil fuel consumption.
Panels A, C, and E: Disturbances in the carbon cycle (C) and atmospheric carbon dioxide concentration ratios (E) due to rapid fossil fuel consumption (A).
Panels B, D, and F: Disturbances in the carbon cycle (D) and atmospheric CO2 concentration ratios (F) due to slow fossil fuel consumption (B). Since fossil fuels are composed of isotopically lighter 12C, fossil fuel consumption provides more 12C to the Earth's surface layer, resulting in a decrease in the 13C/12C ratio of the Earth's surface layer (negative shift of δ13C in C and D). Note that when the consumption rate is high, as in Case 1, the carbon cycle is also highly disturbed (C), and the increase in atmospheric CO2 concentration is rapid and large (E). The atmospheric carbon dioxide concentration ratio is the ratio of the concentration after the increase to the initial concentration. This figure is simulated using the carbon cycle model of Payne & Kump (2007).
Injection speed is an IMPORTANT factor for the deterioration of environments!!
Related Publication: Saito, R., Kaiho, K., Tian, L., Takahashi, S., 2023. Frequent high-temperature volcanic combustion events delayed biotic recovery after the end-Permian mass extinction. Earth and Planetary Science Letters, in press.