Craton Stability: What’s Thickness (and shape) Got To Do With It.

Figure: Image of Depth to Lithosphere Asthenosphere Boundary in kilometers from Cooper et al., 2017.

Shades of blue correspond depth with darker colors corresponding to deeper estimates of the lithosphere asthenosphere boundary. Thick lithosphere is a first-order characteristic of cratons. Though discussions around craton stability primarily focus on buoyancy and rheology, thickness also plays a primary control on both the long-lived nature of of stable cratons and the demise of destroyed cratons. In other words, craton stability is determined, in part, by the material properties of cratonic lithosphere, which set controls on composition and rheology, its thermal structure, and its relative strength in comparison to the material around it and the mantle below. The integrated strength of the cratonic lithosphere, which determines its relative stability, depends on its thickness. Correspondingly, the shape of a craton (or how its thickness varies over a lateral extent) should also play a role in its overall stability. In this talk, I will summarize the connections between craton thickness and (in)stability, the limits on craton thickness, and the consequences of long-lived, thick lithosphere. Finally, I will present new work demonstrating the stability of cratons also depends on their shape.