The Emperors among us

The main lab's view of the last seismic reflection data being collected.
Overseeing them are drawings of Emperor Jimmu and Empress Suiko.

Finishing the seismic reflection acquisition part of our experiment, we find ourselves south of Jimmu Guyot and near Suiko Guyot. The term ‘guyot’ refers to a flat top seamount that was first named by Harry Hess, a pioneer in developing our current understanding of plate tectonics. These features have a similar morphology to the plateaus found in the Western United States with both having a flat terrain on top that is raised above with surrounding areas often by steep slopes. The Hawaii-Emperor Seamount Chain is a great example of the formation of guyots along volcanic chains. Active volcanism is found on the youngest in the chain, currently at the Big Island of Hawaii which sits atop the central Hawaiian hotspot, a small spot in the plate that fuels the volcano from great depths. As the Pacific Plate slowly but steadily moves to the northwest, it carries the islands away from the hotspot, and as they move further away from their main fuel, the island and their volcanoes become extinct. Once the island stops actively growing erosion slowly starts to chip away on the islands, such as found on the islands of Kauai and Oahu, and they become wave-trimmed as they begin to sink. During this time corals grows on the edges and eventually on the top forming atolls, such as found further northwest in the chain such as Kure Atoll and Midway Atoll. Finally, as the atoll continue to sink further under water, the corals cannot survive the greater depths, leaving a guyot behind, like the guyots found in our survey region. Suiko Guyot is known from drilling and dating of samples collected to be ~65 million years old. It can take Hawaiian volcanos up to 2 million years of active eruptions to build up from the seafloor before becoming mostly inactive, so it could be up to ~67 million years ago when Suiko was first over the same source that is feeding the volcanoes of the Big Island.

Jeff cheerfully stows seismic "birds" that were
removed from the seismic streamer as it was
recovered

The Emperor Seamounts are the oldest volcanoes of the Hawaii-Emperor Seamount Chain with each seamount named after the oldest continuing hereditary monarchy in the world, the Emperors of Japan. Jimmu is the legendary first Emperor of Japan was born in 711 BCE and ruled between 660 to 585 BCE. Jimmu and all the emperors to follow are direct descendants of Amaterasu, the goddess of the sun in the traditional religion of Japan called Shinto. Empress Suiko was the first woman to ascend to the Chrysanthemum Throne, where she reigned from 593 to 628 CE. Outside of the political matters, she is known for adopting Japan to a Sexagenary cycle calendar, imported from China which can accurately record time in sixty-year cycles. While we picked our experiment location solely on geologic interests, these legends of Japan bring a long cultural history to surface as well. Japan’s rich and well documented history is too extensive for a single post, much like the long geologic history of the seamounts we are exploring.

We also arrived to the Emperor Seamount Chain at a unique time for Japan’s Emperors. Earlier this month Japan had a new enthronement of Emperor Naruhito after Emperor Emeritus Akihito (the new title of the last Emperor) reported his abdication to the sun goddess Amaterasu as well as his ancestors and other deities. The current Emperor Emeritus also visited the mausoleum of Jimmu in Nara Prefecture back in March to pay his respects before abdicating. This transition marks a new chapter in the traditional Japanese calendar moving from the Heisei era (meaning achieving peace) to the Reiwa era (meaning beautiful harmony). The last Emperor to abdicate was in the early 1800s, marking a rare event for modern Japan. Lastly, the current Emperor Emeritus, like his father before him, has a passion for the marine sciences, publishing over 30 papers on goby fish, a small bottom-dwelling near-shore fish that lives in the Pacific and Sea of Japan. As we continue to finish our experiment on the Emperor Seamount Chain, we are surrounded by both the geologic and cultural history of Earth.

Brian Boston

LDEO