In the Mountains of St Francis – Discovering the geologic events that shaped our Earth
Walter Alvarez
Published by: W W Norton & Co.
Publication date: May, 2008
ISBN: 978-0393061857
List price: £16.99
288 pp
www.wwnorton.co.uk
In 1975, Generalissimo Francisco Franco lay dying on a slab somewhere in Madrid as a party of geology students took a diversion to the Basque capital, Guernica. Sadly, had their leaders known just a little more about art history, they would have known that Picasso’s iconic 1937 painting – the object of our detour – was then still in exile in America.
I had already discovered to my dismay that geologists are capable of driving past any wonder of the world just to squeeze one more roadside ditch into the itinerary, and I remember this misguided diversion because it was such a rare event in my personal geological history. After reading this rich and entertaining book, I am sure this would not have gone so wrong if Walter Alvarez had been leading us.
Alvarez was the principal discoverer of the global iridium anomaly marking the K/T boundary. The story of that discovery, and how it became linked to the extinction of the dinosaurs and to the offshore crater at Chicxulub, Mexico, was recounted in his 1997 bestseller, T rex and the Crater of Doom. The particular “roadside ditch” in which Alvarez discovered the iridium layer is not far from the town of Gubbio, Perugia, Italy. Alvarez has spent a career working in the Apennines trying to discover how that range has been, and is being, created. This aspect of his work forms the subject of his second foray into popular science.
The Apennines have long been a geological conundrum. Their structure is characterised by a series of propagating fold-thrust belts and ramp anticlines. Perplexingly, compressional tectonics at the leading edges of these belts is followed by extensional tectonics behind. This is now believed to be caused by “delamination and rollback” - whereby a slab of deep-lying continental crust undergoes mineral transformations and sinks into the mantle. This downward peeling exerts drag on the crust above, creating compression above the slab’s leading edge, and extension on the trailing.
Alvarez works towards explaining this hypothesis via a personal and scientific journey through many scientific, historical and cultural byways. Rather like an extended field notebook, Alvarez mingles the story of his involvement with Italian geologists with accounts of his travels, his discoveries, and what might be called the “Italian history of science” - in which historical figures, many largely unknown outside Italy, receive credit for thinking of things first.
Although this book will not command lay readers’ interest to the same extent as T. rex and the Crater of Doom, and despite the fact that Alvarez makes no mention of recent work that has debunked Chicxulub as T. rex’s crater of doom, those who venture into the mountains of St Francis in his company will not regret it. The book can certainly be recommended as background reading to all Earth science students frustrated by the occasional cultural lapses of those who lead their field trips.
Ted Nield