A New Chapter in the Study of Plate Tectonics

The surface of our planet is shaped by large tectonic plates that are slowly moving away from each other, towards each other or past each other. Ocean research has traditionally focused on the first two types of plate boundary: mid-ocean ridges, where new seafloor is formed, and subduction zones, where the Earth's crust dives into the Earth's interior. The third type, oceanic transform faults, where two tectonic plates move sideways past each other, has been considered less important. Stresses can also build up at these boundaries and be released in earthquakes. However, transform faults have only about 15 per cent of the theoretically expected earthquake rate. Why there are fewer earthquakes than expected is an open question in the study of oceanic transform faults.

The Significance of Oceanic Transform Faults

The geodynamics of transform faults is the focus of METEOR expedition M204. The research area is located southwest of the Azores in the North Atlantic: the Oceanographer Transform Fault Zone. The aim is to gain new insights into the seismic activity and crust formation along this fault. “Transform faults were previously regarded as conservative plate boundaries, because no seafloor is created or consumed there,” explains Chief Scientist Professor Dr Ingo Grevemeyer, marine geologist at the GEOMAR Helmholtz Centre for Ocean Research Kiel. “However, recent research suggests that these structures are more complex – they could actively contribute to the formation of new crust and involve more complicated geological processes than previously thought.”

Two key questions will guide the scientific team during the expedition. First, why do deep valleys form along transform faults when the spreading rate is low? Can the extension be traced by earthquake processes? Second, why are transform valleys deeper than neighbouring fracture zones? Could this be due to additional magmatic activity before the transform faults become inactive fracture zones?

Long-Term Measurements and Geophysical Investigations

To answer these questions, ocean bottom seismometers and geodetic stations were deployed on the seafloor during the MSM122 expedition of the research vessel MARIA S. MERIAN a year ago. These instruments will now be retrieved during the M204 expedition. Over the past year, they have recorded the seismic activity of the fault zone, providing valuable data on the tectonic stresses in the region. In addition, geothermal and magnetic measurements will be conducted to determine the exact structure and activity of this seismically active fault.

This is the second in a series of six research cruises in the TRANSFORMERS project, which is funded by the European Research Council with €2.8 million. Over the next five years, a team of researchers led by Prof. Dr Grevemeyer will work to reassess the concept of oceanic transform faults and update the theory of plate tectonics.

Expedition at a Glance:

Name: METEOR Expedition M204 TRANSFORMERS

Chief Scientist: Prof. Dr Ingo Grevemeyer

Duration: 27 September to 20 October 2024

Departure: Bridgetown (Barbados)

Arrival: Las Palmas (Spain)

Research Area: Mid-Atlantic Ridge