The long-term strength of continental lithosphere : "jelly sandwich" or "crème brûlée" ?

Abstract

There has been much debate recently concern ing the long-term (i.e., >1 m.y.) strength of continen tal lithosphere. In one model, dubbed jelly sandwich, the strength resides in the crust and mantle, while in another, dubbed creme brulee, the mantle is weak and the strength is limited to the crust. The different models have arisen because of conflicting results from elastic thickness and earthquake data. We address the problem here by first reviewing elastic thickness estimates and their relationship to the seismogenic layer thickness. We then explore, by numerical thermomechanical model ing, the implications of a weak and strong mantle for structural styles. We argue that, irrespective of the actual crustal strength, the creme-brulee model is unable to explain either the persistence of mountain ranges or the integrity of the downgoing slab in collisional systems. We conclude that while the creme-brulee model may apply in some tectonic settings, a more widely applica ble model is the jelly sandwich.