Every day we are bombarded with information about what is happening on the surface of the Earth. But about the Earth itself, we know very little, other than to report about an earthquake or to try to find out more about a mineral resource. We could almost forget that the Earth is a rocky planet subject to very specific natural laws and that it has shaped our history. Those who know it best are the geologists who survey and examine it. Frédéric Boulvain, Professor of sedimentary petrology at the University of Liège invites us to take a look at one of these fascinating surveys.

The title of the book 'Géologie générale', published by Ellipses (1) leaves no room for doubt: this is an introduction to geology. Frédéric Boulvain, who has taught geology at the University of Liège for years wanted to the book to be: 'An introduction to geology aiming to provide the reader with the essential foundations for the study of the Earth Sciences.' No prior knowledge of this multi-faceted discipline is therefore necessary in order to start reading this book. The author's approach facilitates this even further. The book is basically a story which is told with increasing complexity and scale, from crystals and minerals up to the Earth as a whole.

From crystals to rocks

Before diving into the heart of the subject, the author first provides the outlines: what is geology? It is an Earth Sciences discipline (alongside geophysics, geochemistry, geodesy, etc.) which focusses on three aspects: understanding of the Earth's crust, analysis of the processes which take place on the surface and inside the Earth, and finally identification of the chronology of these events. We immediately understand that geology is, therefore, necessarily an interdisciplinary science, at the crossroads of all major scientific disciplines. This is what the short history of the discipline demonstrates, at the start of the book. The first 'geologists' were naturalists - the Dane Sténon who, in 1669 opened the door to stratigraphy (all geological layers are more recent than the one below them) and Buffon who understood that the oldest mountains were magmatic in origin and that our planet therefore went through a molten stage. Quickly skimming through the various trends of thought over the centuries, Frédéric Boulvain lingers on the origin of the continents and tectonic plates which he considers as a considerable break in the history of the discipline. Although there may have been precursors, it is undeniable that Alfred Wegener (1880-1930) was the real author of this theory, which he published in 1915. The theory remained very controversial for a long time until after the Second World War, when physics came to its rescue by showing that it could prove that the Earth's crust was mobile.

(1) Géologie générale. Du minéral aux géosphères. Frédéric Boulvain, 2013, Ellipses, 238 pages.