By Ian Sanders

This Dunedin Academic press guide provides, at an introductory level, a succinct and readable guide to metamorphism. As readers will know, metamorphic rocks are one of the three main types of rocks.

The others are igneous and sedimentary rocks, which may be the subjects of the heat and pressure (often at huge depths within the Earth’s crust) that transforms them into metamorphic ones. For example, mudstone may be changed to slate and limestone to marble.

In Introducing Metamorphism, the author explains how and why rocks change during metamorphic processes. In particular, he discusses the role of water in metamorphism and describes the different types of metamorphic processes, including contact, shock and high-pressure metamorphism, and metamorphism in areas of mountain building and at the roots of those mountains.

He also covers the metamorphism that occurs at the impact sites of giant meteorites, which, since the implication of a massive bolide bringing the Mesozoic to a premature end, is a topic that has occupied and enthralled the minds of both scientists and the public alike.

As is always the case with Dunedin, the guide is illustrated with copious colour photographs and diagrams. And, as always, it uses clear and simple language that will help anyone gain an understanding of metamorphic processes, no matter what knowledge they may have before starting the guide.

In particular, it is divided into sections, which cover:

• The petrology of metamorphic rocks; interpreting mineral changes and textures.
• Aureoles, orogenies and impacts.
• Several case studies in geothermobarometry (the science of measuring the previous pressure and temperature history of metamorphic and intrusive igneous rocks).
• The interior of the Earth.
• Chemical formulas of minerals.
• Minerals under the microscope.
• Microbeam and X-ray methods of studying rocks and minerals.
• The principals of isotopic dating (that is, geochronology). It also includes a glossary of the technical terms used (which have been kept to a minimum) and a list of further reading, for those wishing to take the subject further.

Ian Saunders is a fellow emeritus of Trinity College Dublin, where he has taught for many years. He is also co-editor of the second edition of the Geology of Ireland.

Introducing Metamorphism, by Ian Sanders, Dunedin Academic Press Ltd, Edinburgh (2018), 148 pages (paperback), ISBN: 9781780460642