A drawer from John Woodward’s cabinet

A history of the world set in stone

Popular geology writing is as old as the geological sciences themselves

This article is taken from the November 2023 issue of The Critic. To get the full magazine why not subscribe? Right now we’re offering five issues for just £10.

In the beginning there was Stephen J. Gould, followed by Richard Fortey — at least, many now regard these two as the pioneers of popular accounts about fossils and travel. It’s a genre that never goes away, as shown by the spectacular success last year of Thomas Halliday’s Otherlands: A World in the Making.

In truth, this history of popular geology writing is as old as the geological sciences themselves. Take Hugh Miller’s Old Red Sandstone (1841, and still in print). Charles Darwin’s long series of popular writing started with a travelogue of his voyage aboard the Beagle. What does Ken McNamara’s Unearthing the Underworld add to an already busy bookshelf?

Unearthing the Underworld: A Natural History of Rocks, Ken McNamara (Reaktion, £18)

The answer lies in the subtitle: A Natural History of Rocks. McNamara attempts to tell us, through rocks, about how life and Earth co-evolved over the last four billion years or so. This is a much greater challenge than writing about charismatic fossils with big teeth, whose names and appearance are often well known to us.

McNamara has had to make sand interesting — a challenge. He has also resisted the temptation of making the book a personal journey or travelogue, although we can infer that he has spent rather a lot of time in both Western Australia and the UK.

The story starts with John Woodward’s cabinet of rocks, housed in the Sedgwick Museum of Cambridge. McNamara takes us through some of the early attempts in the mid-17th century by Woodward and others to understand what different rocks — primarily sediments and volcanic lava — could tell us about the world before and during the Deluge.

We then switch to orbital cycles and how the astronomical shakes, wobbles and rolls of the Earth’s journey around the Sun can be detected in the changing pattern of sediments. We learn about the Serbian pioneer Milutin Milanković, but sadly miss out on the earlier figure of James Croll. An autodidact, he took a job as a night custodian in what was to become Strathclyde University so that he could access the library, before ultimately becoming a published author and Fellow of the Royal Society.

McNamara then tackles the microbial world, taking us to modern lagoons in Western Australia where some exotic environments host the same microorganisms and sediments that we can find in the first three billion years of Earth’s history. We then move smoothly into limestones, together with the parallel role of microbes and carbon dioxide in their formation.

We travel in time from 3.5 billion years ago up to the modern period: the white cliffs of the Channel coast unwrap the role of different microbes in their formation, together with the flints that were an essential material for early hominids.

This is a brave attempt to write a popular book about the origin of sedimentary rocks

After carbon dioxide, we meet oxygen. Again we go back in time to the early microbial world to learn about how our atmosphere became oxygenated and how most of the Earth’s mined iron ore deposits formed. Then comes sand, starting with the Stone of Destiny. This is revealed to be a 400-million-year-old block of sandstone, formed when rivers drained the Old Red Sandstone continent that stretched westwards from Scotland to Wyoming, and eastwards to the Ural Mountains.

Taking Western Australia as an example, we follow the deposits of a similarly ancient river and its early land life from its headwaters in even older mountains to its ancient meeting with the sea. Along the way we learn about quartz, that most durable and incorruptible of minerals, which survives endless transport to be concentrated in beaches.

We then cover all the diverse forms of concretions or nodules, which form when a generally oval solid object — from smaller than an egg to bigger than a bus — grows within sediments after deposition. This is introduced using the sarsen stones of Stonehenge, which formed as hydrated quartz deposited from the pore water trapped in chalk to create highly attractive and extremely durable stone much prized for building.

We finish the oxygen story by moving forward to just 360 million years ago: the evolution of the first forests of large trees on Earth can be reconstructed from the presence of charcoal amongst the debris on the forest floors.

This is a brave attempt to write a popular book about the origin of sedimentary rocks and what they tell us about past and present life on Earth. It is not an easy story to tell, since it’s mostly about microbes. If you are interested in life, landscape and the environment, it is a must-read. The lavish colour illustrations help bring these lifeless rocks to life.

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