[M-IS03] Astrobiology

[MIS03-06] Water and carbon cycles in the Earth’s interior and their linkage to the long-term surface environments

★Invited Papers

*Ikuo Katayama¹ (1.Department of Earth and Planetary Systems Science, Hiroshima University)

Keywords:Water cycle, Carbon cycle, Earth’s interior, Surface environment

Long-term surface environments have been stable throughout the geological history because of the dynamic equilibrium of the water and carbon cycles in the Earth’s interior (e.g., Tajika and Matsui, 1992; Kasting and Holm, 1992). Water and carbon is released by volcanic degassing, but they are trapped in the oceanic plates and transported into the mantle at subduction zones. Dynamic equilibrium between the output and input of water and carbon budgets in the Earth's interior have attributed to maintain a stable environment at the Earth's surface. However, the equilibrium might be broken down due to the loss of heat source in the Earth's interior that acts as a driving force of the material circulation. Recent geophysical observations have reported numerous evidences of seawater penetration into the mantle due to faulting in the outer-rise region where the plate is flexured near the trench (e.g., Grevemeyer et al. 2018). Given the rapid reaction rate of the mantle for aqueous fluids, water and carbon can be trapped in the oceanic mantle along the outer-rise faults. In such a case, the dynamic equilibrium of the water and carbon cycle may have broken on the present-day Earth. The global material cycle and self-regulating mechanisms have attributed a stable surface environment, but we may be facing a major tipping point and are considered to be moving into an irreversible and unstable state. In this talk, I will explain this hypothesis based on the latest update of geophysical observations and experimental data, and discuss how global environments change owing to the breakdown of dynamic equilibrium of water and carbon cycles.