There is undoubted excitement and intellectual challenge in trying to understand the Earth’s physical and mechanical processes, yet are we always aware that these efforts are bounded by the fact that what we are studying has the characteristics of an underdetermined system? It sometimes seems, with the relative sophistication of modern techniques in Earth science, that there are more variables than there are examples over the Earth that exhibit the full range of parameter space. For example, it is recognized that rifted continental margins fall in a spectrum from ‘volcanic’ to ‘non-volcanic’ and numerical modelling leads us to suspect that...

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