The Ends of the World Volcanic Apocalypses, Lethal Oceans and Our Quest to Understand Earth's Past Mass Extinctions

Aaaah... the Apocalypse. Who doesn't love it? The spectacle, the drama, and the foreboding knowledge that – oh, spoilers – everyone dies at the end. There has been no shortage of good eschatological writing in recent years. (e.g. Erwin's Extinction, Wignall's The Worst of Times, or Alvarez's T. rex and the Crater of Doom. Do we really need another pop-science book about mass extinctions? Given the continued developments in our understanding, and given that you get all five for the price of one, I'd say yes. As far as I can tell the last comparable book was Hallam & Wignall's 1997 Mass Extinctions and their Aftermath, which was a more academic treatise. So, get your bucket of popcorn ready and roll on the Apocalypse!

Extinction and speciation happen, geologically speaking, continuously. You may have come across the term "background extinction rates". But the geological record reveals there are episodes when species diversity suddenly plunges, and a significant proportion of life forms disappear around the globe. If the concept of extinction didn't really exist until Cuvier put it forward in 1796, the idea of sudden mass extinctions didn't really catch on until Walter Alvarez and his team published their idea of death by comet in 1980 (see also Kolbert's The Sixth Extinction).

The Ends of the World is Brannen's first book. He has set himself the ambitious target to give an overview of what we currently know of the Big Five mass extinctions by interviewing scores of scientists.

In nimble prose that is readable and amusing (I found myself sniggering throughout the book) he walks us through them chronologically, starting off with the oldest. Without repeating the many fascinating details and ideas covered, if there is one thing that all these events have in common, it is that there never is just a single cause. All of these events are characterised by an extraordinary set of circumstances coming together to create some truly challenging conditions for life on earth. And, despite the popular notion of asteroid impacts, most often the threat has come from within. Twice in the form of ice and anoxic (i.e. oxygen-starved) seas at the ends of the understudied Ordovician (445 mya) and Devonian (two extinction pulses 374 and 359 mya), together with a raft of other circumstances. Twice in the form of volcanism-induced global warming with accompanying misery at the end of the Permian (252 mya) and Triassic (201 mya). And then, of course, the asteroid impact at the end of the Cretaceous (65 mya).

Brannen does an excellent job giving airtime to different viewpoints and theories, because above summary is very brief, and the science isn't all settled on this. Even the by now widely accepted asteroid impact hypothesis is more complicated than that. When Alvarez et al. published their theory in 1980, it was met with disbelief and scepticism. And scepticism is good. It has forced the scientific community to gather more data to see if this idea could be supported. By now enough supporting evidence is available and we have located the site of impact. But other, similarly massive impacts have not caused any mass die-offs, giving more credence to the ideas of a few vocal critics who think earthquakes in the impact's wake ramped up episodes of ongoing volcanism.

If there is anything that ought to be highlighted in Brannen's writing, it is how he manages to convey the absolute vastness of the time scales we are dealing with. Consider that all of recorded human history, all the thousands of years, have taken place in the most recent interglacial period, which is only one of twenty such balmy 10,000-year intervals in the earth's most recent 2.6 million year ice age, and you will come to understand that to be a geologist means changing your perception of time.

The other thing Brannen does exceedingly well is evoke the sheer scale of the destruction that has been wrought in the distant past. If you thought the 2013 Chelyabinsk meteorite was frightening, buckle up for the end-Cretaceous impactor. Similarly, the volcanism that wiped out some 95% of all life-forms at the end-Permian, making it the single most destructive event in the history of life, is hard to fathom. Forget the picturesque volcanoes that you know: continental flood basalts are literally the earth puking out its guts and covering whole continents with lava that gets stacked up miles high. As we have never witnessed these rare events, they defy comprehension.

Having discussed the Big Five, Brannen is not quite done yet. This book would be incomplete if it didn't mention current biodiversity loss. There is an eerie correlation between our ancestors arriving in new regions and megafauna disappearing. The overkill hypothesis (see Martin's Twilight of the Mammoths), has not been well received by politically correct anthropologists and social scientists, but I see no problem with it.

Even so, it's interesting to read that many palaeontologists don't consider this the sixth extinction. Yet. They all agree that we are inflicting tremendous damage to our environment and have caused the extinction of many species. And the fact that we are exerting multiple pressures means we could pass a tipping point somewhere along the line. But the current losses pale in comparison with the truly staggering losses incurred during previous mass extinctions. It's way too early, and overly dramatic, to already talk about a sixth mass extinction, as much as it makes for juicy headlines. In the long run, this may make for no more than a blip in the geological record.

Throughout the book, Brannen skilfully highlights the relevance of studying Earth's deep history to the here and now. The tempo with which we are burning fossil fuels like there is no tomorrow is comparable to episodes of large-scale volcanism of the past. Deep history teaches us how the planet's climate will react. The geochemistry is simple and uncontested, and our planet has been here many times before. Natural geochemical cycles can mop up this excess, but these cycles play out on time scales of hundreds of thousands of years. As some scientists point out here, it is far more likely that our civilization will buckle under the strain of overpopulation, failing agricultural systems and climate refugees well before we can release comparable amounts of greenhouse gases.

What could have been a book of doom and gloom has become a phenomenally good read in the hands of Brannen. His writing is witty and irreverent in places and had me both amused and intrigued throughout. His balanced coverage of this massive topic is excellent, giving voice to the many opinions and ideas currently circulating. If you want an up-to-date picture of what we know, this is the best place to start in my opinion.