The theory of plate tectonics describes how the surface of Earth is split into an organized jigsaw of seven large plates1 of similar sizes and a population of smaller plates whose areas follow a fractal distribution2, 3. The reconstruction of global tectonics during the past 200 million years4 suggests that this layout is probably a long-term feature of Earth, but the forces governing it are unknown. Previous studies3, 5, 6, primarily based on the statistical properties of plate distributions, were unable to resolve how the size of the plates is determined by the properties of the lithosphere and the underlying mantle convection. Here we demonstrate that the plate layout of Earth is produced by a dynamic feedback between mantle convection and the strength of the lithosphere. Using three-dimensional spherical models of mantle convection that self-consistently produce the plate size–frequency distribution observed for Earth, we show that subduction geometry drives the tectonic fragmentation that generates plates. The spacing between the slabs controls the layout of large plates, and the stresses caused by the bending of trenches break plates into smaller fragments. Our results explain why the fast evolution in small back-arc plates7, 8 reflects the marked changes in plate motions during times of major reorganizations. Our study opens the way to using convection simulations with plate-like behaviour to unravel how global tectonics and mantle convection are dynamically connected.
At a glance
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Extended data figures and tables
Extended Data Figures
- Extended Data Figure 1: Maps of the surface of a snapshot from a convection model with a yield stress of 150 MPa and of the plate layout of Earth. (137 KB)
a, Map of sea-floor age with the youngest ages in red characteristic of mid-ocean ridges and the oldest zones in blue characteristic of subduction zones. m.y., millions of years. b, Map of non-dimensional horizontal divergence, with divergence zones (mid-ocean ridges) shown in red and convergence zones (subduction zones) in blue. c, d, Maps of the plate sizes of the convection model (c) and Earth (d). The plate size categories are determined in Extended Data Fig. 3.
- Extended Data Figure 2: Subsurface temperature of a convection model with a yield stress of 150 MPa showing a diffuse plate boundary. (475 KB)
a, Global temperature (colour scale) and surface velocities (arrows). The dark zones represent subduction zones and the light zones indicate mid-ocean ridges. b, Zoom-in of the red boxed region in a showing a diffuse boundary; the steady lateral change of velocity directions (red arrows) characterizes the intraplate diffuse zone (grey shaded area), allowing the determination of a diffuse boundary (black dashed line).
- Extended Data Figure 3: Plots of the logarithm of the cumulative plate count versus the logarithm of the plate size for the snapshots of model 2 and Earth. (226 KB)
The data for Earth is taken from ref. 2. The plots show the distribution of microplates in light blue, small plates in mid-blue and large plates in dark blue. The equations of the black fit lines and the correlation coefficients R2 are also shown.
- Extended Data Figure 4: Plot of the fraction of large plates adjoining a triple junction versus the type of triple junction for model 2 and for Earth. (218 KB)
The data for Earth is taken from ref. 2. The red rectangles correspond to model 2 and the black circles to Earth. The coloured backgrounds indicate of dominance of each boundary type: blue shows triple junctions that are mainly composed of subduction zones, red shows the dominance of mid-ocean ridges or transform boundaries and green the dominance of diffuse boundaries. T, trenches; R, ridges; D, diffuse boundary. We added a type of triple junction T(RRR); these triple junctions are directly connected to curved trenches and produce back-arc basins with small plates, hence they are included in the area of the plot dominated by subduction zones. The error bars represent the standard deviation of the fraction of large plates around a triple junction for model 2 and Earth.