Australia: The Land Where Time Began

A biography of the Australian continent 

Basal Drag from Convecting Mantle Shifted the Cratonic Root Beneath North America

The oldest geologic features on Earth are stable continental cratons, which have survived through 3.8-2.5 Gyr of the history of the Earth (Yuan & Romanowicz, 2010; Lee, Luffi & Chin, 2011). Their strong, thick lithospheric roots, which are neutrally or positively buoyant with respect to the surrounding mantle, are the key to the preservation of cratons (Carlson, Pearson & James, 2005; Eaton & Perry, 2013). It is believed most of these cratonic roots dating from the Archaean have remained stable since their formation (Lee, Luffi & Chin, 2011; Carlson, Pearson & James, 2005; Pearson et al., 1995). In this study a combination of gravity, topography, crustal structure and seismic tomography data were used to show that the deepest part of the root of the craton beneath the North American Superior Province has been shifted about 850 km to the west-southwest in relation to the centre of the craton. Kaban et al. have shown by the use of numerical model simulations that basal drag induced by mantle flow could have caused this shift, which implies that cratonic structure can be influenced by mantle flow. Kaban et al. suggest that the conventional view that cratons are static features that don’t evolve is contradicted by their observations. Kaban et al. have concluded that significant interaction could occur between deep continental roots and the convecting mantle.

Sources & Further reading

1. Kaban, M. K., W. D. Mooney and A. G. Petrunin (2015). "Cratonic root beneath North America shifted by basal drag from the convecting mantle." Nature Geosci 8(10): 797-800.