Committee Members Information

• Ph.D. Advisor: Sigurjon Jonsson
• External Examiner: Anne Briais
• Committee Chair: Frans van Buchem
• 4th Committee Member: Froukje van der Zwan

Abstract

Mid-ocean ridges are a fundamental element of the Earth’s plate tectonics, where oceanic crust forms as plates diverge. Although they are globally important, most of our knowledge comes from studying mature ridges, where processes have reached a steady state. Due to their remote locations, many of these ridges remain understudied, leaving key questions unanswered. This thesis applies multidisciplinary approaches to investigate a part of the northern Red Sea, one of the youngest ocean basins on Earth. The study focuses on two key areas: the Mabahiss Deep and the Zabargad Fracture Zone, a major offset of the Red Sea axis, whose structure is still debated due to a lack of high-resolution bathymetric data and extensive evaporite cover. The Zabargad Fracture Zone may pose a significant seismic hazard and risk due to the possible presence of transform faults and its proximity to coastal communities. Using newly acquired high-resolution multibeam bathymetry, complemented by Autonomous Underwater and Remotely Operated Vehicles surveys, petrographic analyses, and integration with previously published data, this research first confirms that the Mabahiss Deep is an active mid-ocean ridge segment hosting a volcano with a caldera and recent volcanic activity. South of Mabahiss Deep, two additional ridge segments are found, likely connected with non-transform offsets. The Zabargad Fracture Zone consists of a young, 50 km long transform fault, with a potential of generating a magnitude 6.7 earthquake, bordered by an older shear zone. To complement the field observations and results, a series of analogue models was designed to explore how ridge-segment spacing, overlap, and evaporite cover influence ridge-transform interactions. These experiments demonstrate that pre-existing weaknesses facilitate the formation of transform faults and that salt layers influence surface morphology while preserving major tectonic structures. The experiments also reveal that salt deformation caused by basement fault activity generates new structures that likely align with the local kinematics, supporting the interpretation of bathymetric data. Together, these studies address a key gap in understanding the structure and development of the northern Red Sea ridge axis and the Zabargad Fracture Zone, and they may serve as a reference for other ultra-slow spreading ridges worldwide.