There’s been a lot of Earth science around this week (there always is) and even if you haven’t been aware of the five earthquakes of at least magnitude 6 this week, or the various ongoing volcanic eruptions, there’s one aspect you can’t have missed during the week of 15-21 November, 2018. California’s horrendous wildfires are a classic example of an interaction between different parts of the Earth system.
This week I’m dodging around a bit — looking at California, at a so-called ‘supervolcano’ in Italy and at the largest earthquake of this week. So — three articles, three continents, three natural hazards and three different aspects of the system in which we live.
California’s Wildfires and Climate Change
The wildfires in California have left dozens dead and over a thousand missing, making them the worst disaster of this nature in US history. Wildfires are natural and have been around since long before humans, although human intervention, either careless or malicious, can be a contributory factor.
While there’s probably a case to make that the extent of the death and devastation is, in part, related to the increasing numbers of people living in vulnerable areas, there’s also a question about whether these fires are becoming more frequent because of a changing climate.
Again we can argue that changing climate may be natural. I’m kicking myself for not having bookmarked an article I read some years ago which argued that the settlement of California took place during an unnaturally wet period and that what we now regard as drought is in fact the normal state. But whether or not this is the case, changing climate does look likely to have implications for wildfires in the future.
It’s too early, of course, for detailed scientific study on what’s still a current state of affairs, but my own thoughts on the subject were echoed by an article in Scientific American this week. The magazine contacted climate scientists who gave their thoughts on the fires which followed “the warmest summer in more than 100 years of record keeping”.
There are many variables affecting the occurrence and extent of such fires, which may be influenced by local weather conditions, but the influence of climate change is certainly one of them. One scientist interviewed observed that “we know that these events are affected by the weather and the climate and how dry it is. The climate system has been altered by people … all the weather we’re experiencing and what’s driving these wildfire events is climate change.”
As a footnote, it’s worth observing that even when the fires are extinguished, the interaction in the system continues. This week the BBC reported on concerns that the loss of vegetation might have adverse impacts on atmospheric carbon dioxide. The forests absorb CO2 so that significantly reducing their extent through fire (as through other methods) removes a carbon sink and increases the levels of atmospheric CO2…increasing global temperatures.
Campi Flegrei: Italy’s Supervolcano
Dr Janine Krippner, volcanologist, science communicator and one of my scientific inspirations, was collecting outrageous headlines over on Twitter this week. There are some crackers. “Study warns if the Earth keeps sucking up its oceans, the planet might explode,” cautioned the New York Post, while the ever-entertaining, though not always reliable, went for a more cautious: “Yellowstone VOLCANO WARNING: ‘time traveller’ from year 6491 in apocalypse prediction”.
I had to check that both of these headlines are real (they are, though they don’t accurately represent the scientific research on which they report). But they are indicative of how easily we react to signs of impending doom regardless of the probability of that doom ever happening.
There are several supervolcanoes on Earth and most of them aren’t widely known, and they can be approached in a rather more measured fashion that the tabloids tend to do. One of these is the Campi Flegrei, near Naples, and this week National Geographic reported that “Italy’s government has raised the volcano’s threat level from green to yellow, or from quiet to requires scientific monitoring”.
This change is based upon the results of a study in Nature Communications, which shows that there has been increasing activity beneath the Campei Flegrei and that “magma could be approaching the at Campi Flegrei” i.e. the point at which eruptions might occur.
It’s worth a little context here. In the first place, the authors of the study acknowledge that the processes which they are reporting are poorly understood. In the second place, the Campi Flegrei has a history of episodic unrest that hasn’t resulted in a much-feared eruption and, in fact, hasn’t erupted in almost 500 years .
That said, an eruption in this area would be a significant issue, not necessarily because of its magnitude (which could be relatively minor) but because of the number of people who would be affected by it.
Earthquake of M6.7, Fiji
Meanwhile, on the other side of the world, a significant earthquake occurred between the island groups of Fiji and Tonga. It occurred at a depth of over 530 km and the information available from the United States Geological Survey’s earthquake summary page suggests that it was caused by lateral movement somewhere close to the margin between the Pacific and Australian plates, where the former descends below the latter along the Tonga Trench, hundreds of km to the west, or else by some kind of deformation deep within the crust
Though large, at M6.7, it was felt by only an estimated million or so people, and then only weakly. I’ve seen no reports of damage. The reason for including it here is that it illustrates the other side of the coin when we talk about hazard.
Both the actual example of the wildfires in California and the potential example of an eruption, even a minor one, of the Campi Flegrei, are significant in themselves, as is the Fiji earthquake. It’s the human impact that turns a natural occurrence into a natural disaster.