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Research Group Division of Earth and Planetary Materials Science


Quantum-beam Earth Science and Technology Group

•Associate Professor Akio Suzuki, specializing in Magma generation and its nature, Phase transition, and Radiation of light
•Assistant Professor Tatsuya Sakamaki, specializing in High-pressure Earth science

Elucidation of the internal structure and chemical evolution of the Earth and planets from ultra-high pressure and ultra-high temperature experiments

The inside of the Earth is an extreme environment with high temperature and high pressure. Under such extreme conditions, not only is the density higher than that of substances on the surface, such as graphite changing to diamond, but also changes in physical and chemical properties due to changes in atomic arrangement and electronic state.
In our laboratory, we are investigating what kind of properties it is composed of substances, how it is formed, and how it has evolved by experimentally reproducing the temperature and pressure conditions inside the Earth and other planets.

4.6 billion years ago, the early Earth's surface was covered with magma ocean. It is also believed that there were events that affected the evolution of the Earth, such as the Giant Impact, which is the most prominent origin of the Moon. In order to clarify the history from such a state to the formation of the present Earth, how magma ocean solidified under the deep conditions of the Earth, separated into rocks and metals, and a layered structure was created. Therefore, we are investigating the evolutionary process of the Earth by melting the material that is thought to have made the early Earth under high pressure. These techniques can also be applied to the evolution of other terrestrial planets.

Fig. 1. Layered structure of Earth’s interior

It is known from the seismological observation that the current internal structure of the Earth has a layered structure (Fig. 1). The central part is called “core” and is made of a metal whose main component is iron. The core is covered with a rocky “mantle”, and the surface of the Earth is a thin “crust”. Due to the vastly different components of each layer, the physical and chemical properties are discontinuous at each layer boundary.

Fig. 2. Schematic diagram of Earth’s inner structure

Not only vertical discontinuities but also horizontal inhomogeneities have been observed (Fig. 2). Such discontinuities and inhomogeneities inside the Earth reflect changes in the properties, varieties, and combinations of substances existing in the Earth. It is believed that large-scale circulation within the Earth, such as subducting plates and updrafts from the bottom of the mantle, is deeply involved.

Fig. 3. High pressure apparatus installed in our laboratory

In order to clarify the whole picture of the Earth in a wide range of time (from the beginning of formation to the present) and space (from the surface to the center), we conduct high-pressure and high-temperature experiments using multi-anvil apparatus (Fig. 3) and diamond anvil cell. In particular, we are working on various problems related to the inside of the Earth by focusing on in-situ observation of substances under extreme conditions at several experimental facilities (e.g., SPring-8, KEK, J-PARC) where quantum-beam (e.g., synchrotron radiation X-rays and neutron beams) is available.