The following Chapter is devoted to the spatial and temporal organisation of these different types of rocks. In other words, how are they organised to form the 'landscape' as we know it? The author answers this question by presenting the formation of sedimentary basins and mountains, which are in some ways their 'final fate'. A fate which appears to be temporary because a chain of mountains is formed quickly (in geological terms) in a few tens of millions of years ... and can disappear just as quickly through erosion. 'In other words,' concludes Boulvain, 'the current appearance of our planet is only temporary ...'

History of the Earth

And so our Earth has been formed. The author could of course, have stopped here with his introduction to geology. However, the last three chapters of his book are, perhaps, at least for the layperson, the most captivating.

They initially provide a radioscopy of our planet. Here, the reference framework has changed because we only know about the inside of the Earth, for a large part, indirectly: 'the deepest surveys barely go beyond 12km' Boulvain reminds us, 'which is only 1/531 of the radius of the Earth! ' He therefore presents the methods used initially to quantify our planet (form, dimension, mass, density) then looks at what meteorites and, above all, the study of earthquakes teach us (see also below in terms of the author's second book). The author then addresses the problem of terrestrial magnetism. What problem? Although we know that the polarity of the terrestrial magnetic field has been reversed on several occasions, we still don't know why. Finally, the author addresses the description of geological cycles at work on our planet. Water and carbon of course, but also silicium for example and, above all, the concept of how these elements survive in the oceans. Thus, although rivers carry relatively few Na⁺ and Cl^- ions towards the oceans, the oceans contain relatively a lot: these elements are not, in effect, either used by the organisms nor incorporated into the sediment and do not enter into the network of clays during diagenesis as do iron and silicium, for example. Consequence: the resistance time of Cl^- in the oceans is practically infinite, while that of Na⁺ is somewhere in the region of 260,000,000 years! Only evaporation could remove them from the ocean.