Pilar Madrigal, Kaj Hoernle, Brian R. Jicha, Christian Timm, Dieter Garbe-Schönberg, William W. Sager, Folkmar Hauff, Maxim Portnyagin, Gene Yogodzinski; Early Emperor seamount evolution and geotectonics of the northwestern Pacific plate. Geology 2025; 53 (12): 1023–1028. doi: https://doi.org/10.1130/G53477.1
Plate tectonics control oceanography
Plate tectonics is the motion of the big, inflexible plates that make-up Earth’s outer shell (the place we stay!) over the much less inflexible inside of the Earth. It can also be accountable for the bodily evolution of our planet via earthquakes, mountain building occasions, and the creation and destruction of crust by way of volcanism. As oceanographers, this can be very important to know the idea of plate tectonics to have the ability to describe the formation of our ocean basins and different phenomena that happens in oceanographic disciplines different than geology. For instance, it’s plate tectonics and the geology of the seafloor that governs the physics behind ocean currents and how they change.
Geological oceanographers have continued to search out inventive methods to be taught more in regards to the tectonic historical past of our planet (e.g., plate reconstruction fashions, geochemical analyses, matching fossils discovered on a number of continents). Even so, there are some areas of the ocean basins whose historical past has not been effectively constrained on account of a lack of samples. One of these areas is the northwestern area of the Pacific plate (massive yellow space in Fig. 1). This area is home to the Emperor Seamounts of the Hawaiian-Emperor Seamount Chain (HESC; Fig. 2). While we all know a lot about Hawaii as a result of the volcanic islands are lively, populated, and straightforward to pattern, we don’t know a lot in regards to the formation of the northernmost Emperor seamounts as a result of they’re in a distant area of the ocean. An obvious bend within the HESC signifies a clear change within the direction of movement of the Pacific plate (Fig. 2). Thus, seamounts on both facet of the bend could maintain main implications in regards to the evolution of the Pacific Ocean basin.
New samples add to the story
Madrigal and the science workforce set out to map and pattern 4 northern Emperor seamounts that hadn’t been researched earlier than (Meiji, Hanzei, Suizei, and Tenji), along with a few different options known as volcanic elongated ridges (VERs). VERs are options related to volcanism brought on by the separation of two items of tectonic plate (spreading ridges). The workforce used a dredge, a large metallic basket that drags alongside the seafloor accumulating rocks, to finish their sampling. Once the lava samples had been back on the lab, scientists analyzed them for his or her chemical make-up and age to help reconstruct the area’s tectonic historical past.
Age-wise, the authors discovered that the seamounts had been usually fashioned in chronological order with the options getting older as you progress north (Fig. 3). Chemically, the seamounts and VERs displayed a wide selection of compositions (Fig. 4) indicating that they had been fashioned otherwise than the seamounts to the south and the modern-day lavas produced by the hotspot plume below the Big Island of Hawaii (ocean island basalts, or OIBs). As suspected, the VERs have the chemical composition of mid-ocean ridge basalts (MORB), the sort of rock discovered at spreading ridges. Samples from the 4 seamounts and one other beforehand sampled website (Detroit seamount) show reducing elemental ratios as you progress north indicating the interplay and mixing of VER spreading ridge and hotspot plume sources to totally different levels alongside the Emperor Seamount Chain.
Complex tectonics
Ultimately, this research reveals the area has undergone a advanced tectonic evolution during the last ~82 million years involving volcanism from two sorts of sources, a spreading ridge and a hotspot plume. This highlights that the geology of our ocean basins is consistently altering, altering the bodily, chemical, and organic patterns we could observe which might control issues like our planet’s climate. Therefore, unveiling tectonic historical past permits us to refine our understanding of all oceanographic processes and how their intertwined nature influences large-scale adjustments in different Earth processes.
Cover image is similar as Fig. 3.
I’m a Ph.D. Candidate in Geological Oceanography on the University of Rhode Island, Graduate School of Oceanography. I acquired my B.S. in Geology from Union College (NY). I research submarine volcanoes! I take advantage of the chemical composition of lava to determine what is occurring inside the Earth and how magma is fashioned. When I’m not working with rocks, I get pleasure from studying on the seashore, cooking, and climbing.
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