Formation of a craton - they don't make them like they used to !
Автор: Louis Moresi
Загружено: 2018-04-30
Просмотров: 13054
The theory of plate tectonics describes how rigid plates move on the Earth’s surface but this really only applies to the oceanic plates. The continental crust is generally a great deal weaker and can crumple or stretch in response to movements of the oceanic plates forming mountain belts, rifts and low-lying basins.
Some of the oldest parts of the continental crust are an exception to this generalisation. These are regions that have experienced very little tectonic deformation in several billion years of existence. These cratons are thought to represent regions of greater strength and this contributes to their longevity. There is evidence that the deep lithosphere is as ancient as the crust and is anomalously thick and buoyant (e.g. Jordan,1975, O’Reilly et al, 2001, Cooper et al, 2013, 2016). We also think that the cratons formed from cool, thin lithosphere in the time before plate tectonics began and then thickened and strengthened to the point where they became effectively indestructible.
The problem with this idea has always been to explain how the hot, weak interior of the young Earth could generate enough stress to thicken strong lithosphere. Alternatively, if the lithosphere was weak too, what stopped it from falling apart by gravitational spreading while it cooled and ‘hardened’ ?
In our work, we show how the collapse of the early Earth stagnant lid could have created the cratons in a short-lived burst. This was a one off event that we will not see again.
Beall, A., Moresi, L. Cooper, C. M. Formation of cratonic lithosphere during the initiation of plate tectonics, Geology, https://doi.org/10.1130/G39943.1, 2017
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