crustal growth

here is a neat image showing crustal thicknesses across the planet. The two thickest regions are in Tibet and the central Andes. The colours represent surface elevations.

 

This image is sources from the USGS, but I got it from Cawood et al., 2012. This paper discusses the current state of affairs of their understanding of the evolution of the continental crust. A major question is whether crustal growth was accelerated early in Earth's history, or if it has been more or less steady going. Here are some of the options:

 

I like the style of Condie and Aster, 2010. Buenas hondas. 

Below they show the idea that prior to 3 billion years ago, a different set of processes dominated the formation of the continents compared to the typical plate tectonics that we see today. In these early days, the mantle was much hotter and convection likely occurred at fairly shallow levels. Melting of dense, thickened/dripping, basaltic crust is thought to be the dominating mechanism of continental crustal formation at this time. After the earth cooled down a bit, subduction-as-we-know it took over, and continental crust began to form by andesitic volcanism at subduction zones, with the occasional delamination of the mafic roots.

 Cawood, P.A., Hawkesworth, C.J., Dhuime, B., 2012, The continental record and the generation of continental crust, GSA Bulletin.