★ Supervisor Yusuke Suganuma is a professor at the National Institute of Polar Research and holds a PhD in Science. He was a core member of the research team that led to the international recognition of the Chibanian Age and served as the lead author of the GSSP proposal paper. His previous book “Geomagnetic Reversal and the Chibanian” won the 36th Kodansha Prize for Science Publishing. He also received the Young Scientist Award from the Minister of Education, Culture, Sports, Science and Technology.
★ A geological formation in Chiba Prefecture preserves the record of Earth’s most recent geomagnetic reversal. Between 774,000 and 129,000 years ago, Earth‘s magnetic north and south poles reversed, and a compass would have pointed south. This formation was chosen as the global standard reference point, and the Chibanian Age (meaning “Chiba age” in Latin) was born.
★ The book has four chapters: understanding the geomagnetic field, geomagnetic reversals, what the Chibanian is, and exploring Earth through Chibanian strata. Each chapter includes “Want to Know More!” boxes covering topics such as “Why auroras seen in Japan are red,” “Creatures that use the geomagnetic field to survive,” and “Are there three South Poles?”
★ The author has joined 7 Antarctic research expeditions and 2 Arctic expeditions, camping on the Antarctic ice sheet for over 150 days. He brings frontline research experience into this book.

Why did “Chiba” become the name of a geological age?

A geological formation in Chiba Prefecture preserves the record of the most recent geomagnetic reversal (when the north and south poles switch). This formation was later selected as the global standard reference point for dividing geological time, and the period from 774,000 to 129,000 years ago (Middle Pleistocene, Quaternary) was named “Chibanian” (Latin for “Chiba age”). What exactly is a geomagnetic reversal? Why does it happen? How do the traces it leaves relate to the division of geological ages? This book guides readers through the mysteries of the Earth and the secret of how the Chibanian came to be.

Yusuke Suganuma（菅沼悠介）
Professor at the National Institute of Polar Research, Advanced Research Promotion Division. Born in 1977 in Nagano Prefecture. Graduated from Ibaraki University, Faculty of Science in 2000. Completed the master’s program at Tokyo Metropolitan University, Graduate School of Science in 2002. Completed the doctoral program at the University of Tokyo, Graduate School of Science in 2005, earning a PhD in Science. After serving as a postdoctoral researcher at the National Institute of Advanced Industrial Science and Technology, a specially appointed assistant professor at the University of Tokyo, and an assistant professor at the National Institute of Polar Research, he assumed his current position in 2023. His specialties are geology, paleomagnetism, and paleoenvironmental science. He has joined 7 Antarctic research expeditions and 2 Arctic expeditions, camping on the Antarctic ice sheet for over 150 days in total. He was a core member of the research team that led to the recognition of the Chiba composite section in Ichihara City as a global standard reference point and the birth of the “Chibanian” age, and served as the lead author of the GSSP proposal paper. He is the author of “Geomagnetic Reversal and the Chibanian” (Kodansha), which won the 36th Kodansha Prize for Science Publishing. He also received the Young Scientist Award from the Minister of Education, Culture, Sports, Science and Technology.

Chapter 1: Understanding the Geomagnetic Field
1 What is the geomagnetic field?
2 The invisible barrier protecting Earth
3 Why can we see auroras?
Want to Know More!: Why are auroras seen in Japan red?
4 How is the geomagnetic field generated?
5 The geomagnetic field changes
6 Observing the geomagnetic field
7 Who discovered the geomagnetic field?
Want to Know More!: Ino Tadataka, who surveyed Japan and made maps
Want to Know More!: Creatures that use the geomagnetic field to survive

Chapter 2: The Geomagnetic Field Reverses
1 The geomagnetic field has reversed many times
Want to Know More!: The Laschamp excursion recorded in Lake Suigetsu
2 Why does the geomagnetic field reverse?
3 Who discovered geomagnetic reversals?
Want to Know More!: Are there three South Poles?

Chapter 3: What Is the Chibanian?
1 Finding the Chibanian in Earth‘s timeline
2 How ages are determined from strata
3 How is a GSSP decided?
4 The road to the Chibanian
5 What was the Chibanian like?
Want to Know More!: Let’s visit the Chibanian GSSP

Chapter 4: Exploring Earth Through Chibanian Strata
1 Reading strata reveals Earth‘s past
2 The strata that defined the Chibanian
3 What are marine organisms telling us?
4 What can we see from tiny pollen?
5 The traces of geomagnetic reversal are clearly visible