Compelling evidence indicates that the solid Earth consists of two physicochemically distinct zones separated radially in the middle of the lower mantle at ∼1800 km depth. The inner zone is governed by pressure-induced physics and chemistry dramatically different from the conventional behavior in the outer zone. These differences generate large physical and chemical potentials between the two zones that provide fundamental driving forces for triggering major events in Earth’s history. One of the main chemical carriers between the two zones is H2O in hydrous minerals that subducts into the inner zone, releases hydrogen, and leaves oxygen to create superoxides and form oxygen-rich piles at the core–mantle boundary, resulting in localized net oxygen gain in the inner zone. Accumulation of oxygen-rich piles at the base of the mantle could eventually reach a supercritical level that triggers eruptions, injecting materials that cause chemical mantle convection, superplumes, large igneous provinces, extreme climate changes, atmospheric oxygen fluctuations, and mass extinctions. Interdisciplinary research will be the key for advancing a unified theory of the four-dimensional Earth system.

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四维地球系统的关键问题

令人信服的证据表明，固体地球由两个物理化学不同的区域组成，它们在下地幔的中部径向分离，深度约为 1800 公里。内部区域由压力引起的物理和化学控制，与外部区域的常规行为截然不同。这些差异在两个区域之间产生了巨大的物理和化学势，为触发地球历史上的重大事件提供了基本驱动力。两个区域之间的主要化学载体之一是含水矿物中的 H2O，它会俯冲到内部区域，释放出氢，并留下氧以产生超氧化物并在地核-地幔边界形成富氧堆，从而导致局部净氧增益在内部区域。地幔底部富氧堆的积累最终可能达到超临界水平，引发火山喷发，注入导致化学地幔对流、超级羽流、大型火成岩省、极端气候变化、大气氧波动和大规模灭绝的物​​质。跨学科研究将是推进四维地球系统统一理论的关键。