We seem to hear about some new seismic event almost every other day, and from a quick check of the Web I’m not the only one wondering whether the earth might be falling apart...?
The Google-equipped inquisitive mind finds a figurative tsunami of pages exhorting that recent natural disasters are signs that we are in the "End Times". At time of writing a Google search for "earthquakes, end times" yielded literally millions of results (Well, for me it does anyway)
When pondering Sustainable Human Flourishing, religion of all flavours warrants very serious cogitation, so you can bet that I'll share some thoughts on biblical end times prophecies in later blogs - today though, I want to share an interesting hypothesis that I came across in my search for “the truth” about all those earthquakes, volcanoes, tsunamis, etc...
The most logical place to start such a search is to get the "official story" from the US Geological Survey (USGS). Their site is an excellent resource for all things seismic and they’ve even published a page just to answer this question. I really did try to take heart from USGS assertions that one of the main reasons we appear to experience more seismic activity recently is because we're getting better at measuring it… There is, undoubtedly, wisdom to the USGS's suggestion to "keep calm and carry on", but the inquisitive mind is still left a little unfulfilled.
So I continued my search, and stumbled across a rather intriguing hypothesis. A simple idea, yet one that hopefully is just controversial enough to be the perfect candidate for my first blog post...
Increased seismicity may be a secondary effect of climate change.
Whoa! What? Fossil fuels cause tsunamis? Yeah, right, now I've heard it all!
Well... Ahem... Yes. I do admit that the hypothesised link between climate change and increased seismicity is not testable in any meaningful fashion at the current time (and so I do respect the caution expressed by the USGS), but the basic storyline behind the hypothesis seems almost so simple that it hardly needs testing... Here it is in a nutshell.
Tectonic plates move at different speeds, partly because of their relative sizes and weights. Volcanoes, earthquakes, and tsunamis most commonly happen where the plates bump into or move away from each other. This happens more often in some parts of the world than others – the aptly named "Pacific Ring of Fire" is the classic example where we have lots of different sized plates moving in different directions:
As you see, the Pacific Ring of Fire is completed in the south by the continent of Antarctica and its Antarctic plate.
Antarctica is covered by a heavy ice sheet that is around 1.5 km thick, on average.
According to most recent studies, that ice appears to be melting rather quickly (more below).
So, given these premises, the currently untestable hypothesis is this…
As the Antarctic ice sheet melts (and re-forms) the continent of Antarctica gets lighter (and heavier).
This changes the overall inertia of the Antarctic plate, which changes the dynamics of the other plates around it, and so on…
All this (potentially) contributes to an increase in frequency and/or severity of volcanoes, earthquakes, and tsunamis, (potentially) all around the ring – even half a world away from Antarctica.
Of course, as far as continents go, Antarctica is pretty heavy - as you can see in the contour map below of the thickness of the Earth's crust (numbers in kilometres.) Also, we must consider that the stuff that a continent is made of is significantly heavier than ice…
Important Note: the above is a Mercator projection map that does not give a true representation of the size of Antarctica (or Greenland) - the more honest Transverse Mercator Projection below gives us a sense that the ice in Antarctica and Greenland might not be an inexhaustible resource after all.
Some “back of the beermat” calculations would suggest that Antarctica's approximately 25 million cubic kilometres of ice contributes a not entirely insignificant amount of inertia to the global tectonic balance sheet… To me, it seems like an interesting hypothesis...
So, just how much change are we talking here? Is it enough to worry about?
Well, the best answer that I’ve found to that question comes from the Gravity Recovery and Climate Experiment. GRACE was only launched in 2002, so in scientific terms hasn't been active for too long, but the results already seem pretty scary – According to GRACE, ice in West Antarctica (and Greenland – see below) may be melting at a rate of about 100 cubic km per year for the last few years. Sure, a lot of that comes back during winter, and so at the end of the day, this may mean that only a tiny percentage of their total ice mass is actually lost... Still, one cubic metre of ice weighs a bit less than a tonne, and so that still means that Antarctica could be changing its inertia by close to 100 billion tonnes per year.
If you’re still with me, then I’d like to make a quick observation related to Greenland. Did you notice that Iceland shares a tectonic plate with Greenland, which is losing ice at an even faster rate than Antarctica. Did this contribute to the seriousness of the Eyjafjallajökull eruptions in 2010?
Hold that thought then look again at the first map above - If there is anything to this hypothesis, then the UK, Ireland, much of coastal Western Europe, and East coast Canada/US are in the firing line of a tsunami if Greenland keeps getting lighter - We probably shouldn’t think that this is all about the Pacific Ring of Fire…
Despite the lack of proof today (and climate change deniers aside) I suspect that if you ask an earth systems scientist or geologist about their thoughts on this hypothesis, they will probably give the same answer that a high-school physics student will give – “of course a rapid change in the weight of continent will result in more seismic activity around that continent!”
If you ask them to say how much more, then they will sagely say that it is too early to tell yet – which is not very helpful, of course.
I suspect though, that if you ask people in places like Japan, Thailand, Indonesia, Hawaii, New Zealand, California, etc, then they’ll probably say that they’ve got quite enough already.
I reiterate that there have only been preliminary scientific papers published to call for more research on the topic, so I'm not claiming to have any hard facts here. You should be highly suspicious of my assertion and do some digging of your own.
I also expect that any suggestion of even a tenuous link between climate change and seismicity will draw the typically glib and predictable howls of protest from climate change deniers - if you are one of them, then please allow me to preemptively riposte with this powerful post from Bill McKibben. Bill has done a far better job than I can of expressing how I feel about otherwise rational people who choose to avoid their responsibility to think beyond their own navel.
In closing, no sane person will deny that natural disasters are scary; humans are terrified of hurricanes, floods, volcanoes, earthquakes, tsunamis, and the like.
I'm not trained as a psychologist, but extreme storms, earthquakes and their ilk seem to hit us at our most primeval, lizard-brain level. Even a very average student of human nature like myself can probably attribute some of this fear to a loss of control...
At that level, riding out a hurricane or an earthquake is not so different to being a passenger in an airplane - flying, strapped into your cramped seat in a cigar-shaped tube of metal thousands of metres above the ground in a freezing and seriously oxygen deprived atmosphere - fear is natural. The fact that so many people (myself generally included) are not scared while flying is testament to humanity's admirable capacity to trust our scientists and our engineers over our own lizard instincts.
So, I guess that the whole point of this post is to make us think... Whether the hypothesis is true or not, our scientists have been telling us for a long time that it is very bad idea to keep on melting the Antarctic and Greenland ice sheets. When will we trust them?