Research on magnetic imaging of manganese crusts conducted by Ms. Noguchi, a graduate student at our university, along with Professors Yamamoto and Usui of the Center for Integrated Marine Core Research, has been published in *Geophysical Research Letters*.
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Atsushi Noguchi, then a second-year master’s student in the Department of Science at the Graduate School of Integrated Human and Natural Sciences, along with Professors Yuji Yamamoto and Akira Usui of the Center for Integrated Marine Core Research, conducted research on magnetic imaging of manganese crusts in collaboration with the National Institute of Advanced Industrial Science and Technology (AIST) and Kanazawa Institute of Technology. The results of this research were published in the U.S. academic journal *Geophysical Research Letters* on June 3, 2017.
Manganese crusts are considered important not only as a resource but also as sedimentary rocks that record marine environments and climate change over tens of millions of years. Determining their precise formation ages is expected to enable the accurate reconstruction of long-term past Earth environmental information; however, until now, the only method available for estimating the formation ages of manganese crusts was the use of radioactive isotopes, which is both labor-intensive and time-consuming.
In this study, we performed magnetic imaging of manganese crusts collected from a seamount approximately 150 km southwest of Minamitorishima using a scanning SQUID microscope—the first of its kind developed in Japan—capable of magnetic imaging of geological samples under ambient temperature and pressure.By measuring the magnetic record of past geomagnetic reversals at a high resolution of 0.1 mm, we estimated the precise formation age and determined that the average growth rate of the manganese crust is 3.4 mm per million years. Furthermore, we confirmed that the composition and quantity of magnetic minerals in the sample changed around 3 million years ago, which we attribute to the effects of climate change.
Going forward, further elucidation of the growth process of manganese crusts and the reconstruction of the Earth’s environment over long periods are expected to contribute to predicting future environmental changes.
For more details, please visit the National Institute of Advanced Industrial Science and Technology (AIST) website at Please visit
Manganese crust
A rock composed primarily of iron and manganese oxides that grows like a crust on the surface of exposed rocks on the seafloor.
Magnetic imaging
: The process of visualizing the distribution of magnetic fields generated by the magnetic properties of a sample.
: A rock formed by the consolidation of fine-grained particles, particles produced by volcanic eruptions, fossilized remains of organisms, and chemically precipitated particles.
: A device that uses a highly sensitive superconducting quantum interference device (SQUID) magnetic sensor with a tiny detection coil to image the distribution of weak magnetic fields in the immediate vicinity of a sample surface at the microscopic scale.