Billions of years of plate tectonics have destroyed much of what was the earliest continents. The parts of the continents that remain have survived because their composition makes them buoyant and strong. These blocks known as cratons were thought to be indefinitely stable are now thought to not only break up but can also be fused back together again.
Mantle plumes are eruptions of hot, buoyant material rising up through the mantle and are responsible for the splitting apart of tectonic plates (rifting) and continental break up. A large geological structure called the Mackenzie dyke swarm in a craton of northern Canada was formed by an enormous ancient plume.
Experiments on rocks with similar compositions to the Mackenzie dyke have shown that the magma that formed this structure originated form depths of less than 100 kilometres below the Earth’s surface. Therefore the magma must have erupted through a thin plate. However, studies of the area today reveal a thick plate (about 200km thick) showing that the plate must have thickened after the development of the formation.
The researchers of this study, Liu and colleagues, suggest a mechanism for the thickening of the plate immediately after the dyke swarm formed. They show in their simulations that the residue of the plume responsible for the dyke swarm could have helped to repair the damaged craton, essentially filling thin parts of the plate and cementing it from below. This study indicates that cratons do not simply exist for billions of years, but undergo a more complex history than was previously assumed.