杏吧原创

IN ONE of the Austin Powers films, Austin鈥檚 nemesis Dr Evil hatches an extravagant plan to threaten governments by drilling into the Earth to release streams of red-hot magma. Nought out of ten 鈥� the Earth鈥檚 crust does not float on molten rock. The mantle is solid. Plates do not just melt into the fiery deep. But without Dr Evil鈥檚 fanciful drilling programme, how would we know?

The past year has seen the arrival of some books that provide answers to this and a host of other questions 鈥� required reading for geoscience students and super-villains alike. We know that the Earth鈥檚 mantle is solid because of the behaviour of seismic waves. Dr Evil, along with some authors of general science texts for schools, should read Seth Stein and Michael Wysession鈥檚 An Introduction to Seismology, Earthquakes and Earth Structure. Along with all the classical stuff, they explain the recent advances from tracking plates right down to the core-mantle boundary to describing large-scale deformation of the continents. This book should become a mainstay of many undergraduate courses.

To pursue the causes of earthquakes further, dip into Chris Scholz鈥檚 The Mechanics of Earthquakes and Faulting. This is a fully revamped second edition of a major classic. Scholz now includes modern ideas on how one earthquake can trigger another and how lots of earthquakes over time can allow slip to accumulate along faults.

While the mantle behaves as a stiff solid for seismic waves, over geological time it must flow, causing the movement of the plates. Geodynamics is the application of physics to understanding these earth processes essentially as engineering problems. In 1982, Don Turcotte and Gerry Schubert published their book of the same name.

The long-awaited second edition has the original鈥檚 well-paced mathematical treatment 鈥� the physics of the problems hasn鈥檛 changed 鈥� but the applications are bang up to date. So along with the rheology, heat budget and mechanics, all required for understanding how plates deform and move, come new approaches such as using satellite geodesy to track active deformation of the Earth鈥檚 surface, comparisons with the tectonics of other planets and updated geochemical tools for understanding the mantle.

To find out what most of the upper mantle is made of, turn to page 254 of Ole Johnsen鈥檚 Photographic Guide to Minerals of the World. (OK, it鈥檚 olivine.) While being slick and authoritative, it appears to be aimed at natural scientists of a bygone age. As it says, there are more than 500 minerals described, of which Johnsen considers 200 to be fairly common. Phew 鈥� we鈥檙e lucky if we can get our students to recognise a dozen.

For most geoscience courses a book about rocks is a much better choice. And there鈥檚 a really good one just out: Myron Best鈥檚 Igneous and Metamorphic Petrology. These topics, falling under the umbrella of 鈥渉ard-rock鈥� geology, have lost a great deal of prominence in curricula as departments have sought to address increasingly environmental agendas. Perhaps books like this will begin to redress the balance.

The dangers of neglecting classical areas of geology are addressed in a wonderfully combative essay by John Dewey, one of a collection in Plate Tectonics: An insider鈥檚 history of the modern theory of the Earth. Edited by Naomi Oreskes, the essays are new autobiographical pieces by 鈥渢he scientists who made Earth history鈥� 鈥� rather like Austin Powers coming back from the 1960s. The book is a bit hit-and-miss, but it does provide an interesting commentary once you know some of the science 鈥� perhaps once you鈥檝e read the start of Geodynamics. Groovy baby, yeah!