A Thin Elastic Plate Model for Thermally Contracting Young Oceanic Lithosphere: Insights From Comparison With Modern Seafloor Observations

Abstract

We find at fast- and intermediate-spreading seafloor that their ridge-parallel bathymetric profiles between two neighboring fracture zones, excluding the part of the seafloor inward to fracture zone (FZ) valley, are predominantly upward concave. The temporal evolution of the bathymetric profiles from the lithosphere formed at the Chile Rise is characterized by (a) the rapid growth of the middle deflection to about 200 m relative to the ends for the first few millions of years and (b) a steady state afterward. We show that these characteristics and the upward-concave sense of bending can be reasonably explained as the flexure of a thin elastic plate contracting thermally from the top while cooling. The best-fitting model needs only about 10% of the thermal bending moment based on the half-space cooling model and the free-end assumption. Our model is consistent with the recent observations that oceanic lithosphere is cut open at a FZ valley, which disprove the previous assumption that ocean floor is bent down forming the valley walls.