Marine Magnetic Anomalies Enhanced by Internal Stress in Rapidly Cooled Submarine Basalts

Abstract Marine magnetic anomalies are pivotal to our understanding of plate tectonics, geomagnetic fields, and deep Earth dynamics. However, the question of how Ti‐rich titanomagnetites, the primary remanence carriers in oceanic crust rocks, can faithfully preserve geomagnetic field information for tens of millions of years is not well understood. Here, we combine microscopic, micromagnetic, and rock magnetic analyses, including 14‐T high‐field measurements, to show that the magnetic micro‐anisotropy of a fresh pillow lava dredged from the Juan de Fuca Ridge is dominated by internal stress throughout its chilled margin to its interior. Internal stress, which is generated primarily by the contraction of hot lava erupting into cold seawater, increased the natural remanent magnetization in this lava by a factor of ∼3. We suggest that stress‐induced magnetic domain state transformation from multidomain to single vortex (or single domain) in extrusive pillow lavas significantly enhances oceanic crustal magnetic remanence strength and stability.