6-minute read

Planet Earth is a somewhat unpredictable landlord. Mostly, conditions here are benign and favourable to life, but sometimes its tenants are suddenly crushed in a violent outburst. For as long as humans have lived, we have been subjected to such natural catastrophes and have been trying to both understand and predict them. As marine scientist Dr Ellen Prager shows here, we have made great strides, but many questions and unknowns remain. Dangerous Earth is a fascinating tour to the cutting edge of the earth sciences to look at some of the complex problems for which we are still lacking answers.

Dangerous Earth is a cleverly structured book. Each chapter opens with some examples of famous or scientifically important natural disasters that in hindsight were as surprising as they were full of lessons. Having whetted the reader’s appetite with tales of destruction, Prager then walks the reader through the basic scientific facts and principles necessary to understand a particular branch of the earth sciences. The largest part of each chapter, though, is dedicated to the unknowns: the open questions, the vexing problems, and the limits of our current methods and instruments.

As the subtitle of the book implies, the usual suspects – volcanoes, earthquakes, hurricanes – are all present and correct, but Prager takes the bull by the horns and opens with climate change. And this is actually a sensible approach: she does not go quite as far as McGuire does in his book Waking the Giant, but whether certain natural disasters will be exacerbated by climate change is a question of intense interest.

Briefly introducing climate change basics and the 2002 collapse of the Larsen B Ice Shelf in Antarctica, she quickly turns to the uncertainty around sea-level rise. This means examining what is happening at the poles. From earlier reviews, I was already familiar with the rapid retreat of Greenland’s glaciers, but the book is especially up to date on the complexities of what happens at the interface between glaciers and their bedrock, and at the underside where glaciers enter the ocean. Next to the Thwaites Glacier, she mentions other Antarctic monsters most of us will have never heard of, but that will shape our future. Similarly riddled with questions is how global oceanic circulation will be affected by climate change, which means reckoning with its complex three-dimensional nature. Other matters touched on here are melting permafrost, bleaching coral reefs, and dead zones devoid of oxygen.

“[Dangerous Earth] is especially up to date on the complexities of what happens at the interface between glaciers and their bedrock, and at the underside where glaciers enter the ocean.”

The same approach is applied to the topics of volcanoes and earthquakes. Plate tectonics quite literally underlies both, so is introduced first. These are especially riveting chapters – I don’t think I will ever tire reading of the eruptions of Mount St. Helens or Laki. Meanwhile, Mount Pinatubo and the less well-remembered Nevado del Ruiz eruption also taught the geological community a lot. But the unknowns! What does the plumbing that feeds volcanoes look like? How do eruptions progress and end? What of the idea of the life cycle of a volcano: its birth, growth, and death? What of the risk of so-called flank collapses triggering enormous tsunamis? The new book Volcanotectonics offers more insights.

Earthquakes hold similar mysteries, and this field is particularly known for its attempts at prediction. Not surprising, since many cities have been built on or near faults. Prager reveals fascinating complexities and discoveries: The 1992 Landers event revealed that earthquakes can jump tens of kilometres between known segments to trigger tremors at other, unconnected faults. This has raised many questions about the randomness or relatedness of earthquakes. Do they cluster? Can they occur in swarms? Can human activities such as mining or fracking trigger tremors? Then there are the bizarre slow-slip earthquakes where tectonic plates move over days or weeks rather than instantaneously, without discernible seismic waves. This chapter provides a welcome update to a book such as Earthshaking Science. Tsunamis are bundled into this chapter. Especially the 2004 Sumatra earthquake and ensuing tsunami revealed a lot about the subtle complexities of how seafloor shape and topography – its bathymetry – can channel and redirect wave energy. As Prager writes: “It’s not exactly like dropping a pebble in a pond”.

“Earthquakes hold similar mysteries [such as] bizarre slow-slip earthquakes where tectonic plates move over days or weeks rather than instantaneously.”

What unites these first three chapters is the limits imposed by our short window of observation. Data have only been collected for a century or so, a geological blink of an eye. Many recent disasters have spurred scientists to look into the rock record for evidence of past disasters, revealing many. Some, disturbingly, can be very violent, though very infrequent, sparking new questions and concerns about e.g. supervolcanoes.

Dangerous Earth does seem to run a bit out of steam after this. After three solid 40-50–page chapters, the chapter on hurricanes clocks in at 28 pages. It still does a good job of presenting the atmospheric and meteorological mechanics, as well as the unknowns. Why do some storms intensify so rapidly? What are the links with climate change and known patterns such as El Niño? But especially, can we improve forecasts, both of the path storms will take, and the attendant risk of storm surges?

“our short window of observation imposes limits […] many recent disasters have spurred scientists to look into the rock record for evidence of past disasters, revealing many. “

The final chapter, though, felt like an unsatisfying end to an otherwise excellent book. In just 17 pages Prager mentions rogue waves, landslides, rip currents, sinkholes, and – wait for it – sharks (!). Not only does that last one feel totally out of place in a book on geological hazards, on average literally only a handful of people are killed by sharks annually. Since she notes that landslides are much more common than most people realise, an in-depth chapter on these so-called mass movements would have made for a stronger end. It could have included those sinkholes, but also erosion, avalanches, and land subsidence. Furthermore, it connects back to volcanoes and earthquakes as these are often followed by lahars and mudflows. And there are fascinating but poorly understood phenomena such as soil liquefaction during earthquakes.

That observation notwithstanding, Dangerous Earth is overall a fascinating and riveting read that really succeeds in bringing you right to the cutting edge of open questions in the earth sciences. Concerning prevention and preparedness, she echoes the sentiment in books such as The Big Ones and the recently reviewed Disaster by Choice: that we are increasingly, and foolhardily, putting ourselves in the path of destruction. Many questions remain, but we know enough to prevent a lot of the suffering and damage that accompany most natural disasters.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

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