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Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
13 August 2025, Kiel/Papeete. How do changes in sea level influence geological processes deep beneath the seafloor? Is there a feedback loop between the global climate and the formation and composition of new oceanic crust? These are the central questions being explored by an international research team led by Professors Martin Frank and Heidrun Kopp, both of the GEOMAR Helmholtz Centre for Ocean Research Kiel. Today, the team will set sail from Tahiti aboard the German research vessel SONNE for Expedition SO314.
Over millions of years, as vast ice sheets and glaciers have grown and melted, the global sea level has risen and fallen, changing the pressure exerted on the ocean floor. But what effect do these changes have on geological activity deep inside the Earth?
Modelling studies suggest that volcanic activity along mid-ocean ridges responds to these pressure variations, for instance through changes in the thickness of newly formed crust, the composition of magma, or the intensity of hydrothermal activity, where hot, mineral-rich fluids emerge from the seafloor. However, a lack of long-term time series data from the seafloor has so far made it difficult to confirm these hypotheses directly.
Time series: A Key to understanding the Earth System
“We already have excellent reconstructions of past sea-level changes, but there are no similarly high-resolution records of how geological processes on the ocean floor have evolved over time. This is the gap we aim to close,” says Dr Martin Frank, a professor of chemical palaeoceanography at GEOMAR. Frank will lead an international research team aboard the German research vessel (RV) SONNE for the next eight weeks, studying the Southeast Pacific Rise – one of the fastest-spreading and most active segments of the global mid-ocean ridge system.
“This area of the ocean acts like a conveyor belt for Earth’s geological history,” explains Frank. “We suspect that the processes taking place here have been influenced by climate over geological timescales – for example, through pressure changes driven by sea-level fluctuations during glacial and interglacial periods.”
Volcanic Glass as an Archive of the Deep Earth
Along the ship’s route from Papeete (Tahiti) to Antofagasta (Chile), the team will use a gravity corer to collect sediment cores up to 25 metres long. They will follow a transect running perpendicular to the ridge axis. This closely spaced sampling will provide a high-resolution time series.
“These seafloor sediments contain volcanic glass and metal deposits,” says Frank. “They reveal how magma chemistry and hydrothermal activity have varied over the past 1.5 million years. We can read these changes like entries in a geological archive.”
Meanwhile, seismic measurements conducted during the expedition will help reconstruct changes in the thickness of the ocean crust – another key indicator of how Earth’s interior processes may respond to climate-driven pressure shifts at the surface.
Understanding Earth System Dynamics
Expedition SO314 forms part of the large-scale European ERC Synergy Project T-SECTOR (Testing Solid Earth - Climate Connections), which investigates the links between processes in the atmosphere, the ocean, and the Earth’s interior. Alongside the GEOMAR teams led by professors Martin Frank, Heidrun Kopp and Kaj Hoernle, the project involves Professor Charles Langmuir from Harvard University (USA). Scientists from MARUM (the Centre for Marine Environmental Sciences at the University of Bremen) and the University of Hamburg are also participating in the expedition.
Expedition at a Glance:
Name: SO314
Chief Scientist: Professor Dr Martin Frank
Duration: 13 August – 5 October 2025
Departure Port: Papeete (Tahiti)
Arrival Port: Antofagasta (Chile)
Research Area: Southeast Pacific
www.geomar.de/n9980 image materials
https://www.geomar.de/forschen/fb4/fb4-muhs/schwerpunkte/t-sector T-SECTOR Project
https://www.geomar.de/en/news/article/linking-climatic-changes-and-geological-pr... Press release on T-SECTOR ERC Synergy Grant
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