Plate tectonics is a kinematic description of Earth that treats the outer shell of its mantle as a number of plates or rigid spherical caps that move with respect to each other (see the “Plate tectonics” sidebar). The mantle is the outer, solid 3,000-km-thick shell that overlies Earth’s fluid outer core. An enormous amount of geological and geophysical data has gone into determining the motion ...

The facies changes, tectonics and magmatism across the Triassic–Jurassic boundary in the southern Tethyan margin have been studied in Egypt, Sudan, Jordan and Saudi Arabia. In Saudi Arabia and Jordan an unconformable contact is recognized between the Upper Triassic and Lower Jurassic rocks. This unconformity surface is marked by the truncation of the fluvial clastics of the uppermost Triassic b...

[1] The net influx of water into the deep mantle by plate tectonics has been poorly constrained because it is difficult to quantify how efficiently subducting slabs are devolatilized on a global scale. The significance of deep water cycle in the Earth history is similarly ambiguous because it depends critically on when plate tectonics started and how it evolved through time. Here I show that, u...

We use 1-D thermal history models and 3-D numerical experiments to study the impact of dynamic thermal disequilibrium and large temporal variations of normal and shear stresses on the initiation of plate tectonics. Previous models that explored plate tectonics initiation from a steady state, single plate mode of convection concluded that normal stresses govern the initiation of plate tectonics,...

The realization that Earth may have lost heat more slowly in the past than at present has motivated the search for mechanisms to reduce the efficiency of plate tectonics in the past. Several mechanisms have been proposed, such as the resistance to subduction of thick plates (1) produced by deeper melting at higher mantle temperatures (2). We (3) proposed an alternative mechanism, namely subduct...

erosion phenomenon (plate tectonics process) CESA'98 Nabeul-Hammamet, Tunisia, April 1998 Thomas LEDUC September 1997

The Earth stands out in the solar system as the only planet with plate tectonics. This peculiarity is due not only to strong internal heating but also a lithosphere rheology characterized by brittle failure and localization, as a comparison with Venus clearly show. Localization in the ductile regime are manifested on Earth by ductile shear zones, which have proven difficult to explain theoretic...