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Could We Stop Geologic Disasters?

Rocky Planet iconRocky Planet
By Erik Klemetti
Oct 11, 2017 7:45 PMNov 20, 2019 5:37 AM


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Damaged homes from the 2010 earthquake in Haiti. European Commission DG ECHO. Geologic disasters are commonplace on Earth. Earthquakes, eruptions, tsunamis, floods -- they occur all the time and not without consequence in terms of loss of life and property. Many times, they happen without warning and occasionally in places you might not suspect. So, what can we do to stop these disasters ... and by that, I mean stop them, not prevent damage and destruction in their aftermath. I get this question a lot: can we actually prevent geologic disasters from happening. That volcano looks like its going to erupt? Let's make sure it doesn't! That fault line has a record of big earthquakes and it has been longer than usual since the last one? Let's get rid of the threat. Human ingenuity can solve many massive problems, so why not these? That is the realm of what might be called "geoengineering": attempts to solve problems by manipulating large Earth processes. It really sounds like science fiction, mostly because it is. The processes that drive massive geologic disasters are on such a scale that trying to prevent them with almost any human technology is like an ant trying to fix a Volvo. But let's speculate a bit. How would you even approach the problem? For the biggest geologic disasters (in terms of loss of life and property), the two big players are earthquakes and eruptions. With those events sometimes come tsunamis and landslides, which are massively destructive as well. However, they tend to be caused by earthquakes or eruptions, so they are best dealt with at the source. And the source of all this is plate tectonics. This is the theory that the surface of the Earth is divided into plates of rock. These plates are massive -- thousands to tens of thousands of kilometers across -- thick, reaching 100 kilometers (62 miles) beneath our feet. These plates move on the slowly convecting (but still solid) mantle and at their fastest, only move tens of centimeters per year. These plates can collide to form mountain belts, spread apart to form huge rifts, dive under one another and slide past each other. All of these interactions have consequences: Friction, which cause earthquakes, and upwellings of magma, which forms volcanoes. Luckily, much of the tectonic action of earthquakes and volcanoes are limited to the places where plates interact. This is why Indonesia is a very geologically active area but Ohio is not. It doesn't mean that disasters don't happen elsewhere (hello, Yellowstone or New Madrid), but those are much rarer events. However, day in and day out, the plates are moving. Now, you might say "can we stop tectonics?" The answer to that is a very big NO and we wouldn't want to anyway. So much of the habitability of Earth is likely linked to tectonics, so stopping mountain belts from rising or volcanoes from erupting would not be a good plan ... or one even remotely possible as it is rooted in the convection of magma thousands of kilometers deep of the Earth's mantle. So, can we stop earthquakes and eruptions? We can start with earthquakes. They occur when stress builds on faults in the Earth's crust (mostly) and when that stress exceeds the strength of the rock, then the rocks slip and an earthquake occurs. To get an idea of the energy released in an earthquake, we can compare it to other events. The first atomic bomb used in warfare released about the same amount of energy as a magnitude 6 earthquake. A lightning bolt might be the same energy as a magnitude 2 earthquake. The largest earthquakes on record (magnitude 8 and 9) released as much energy as almost 1 million Hiroshima bombs. That's a lot of stress stored in the faults and released when they rupture! Could we bleed off the stress somehow? One suggest might be to drill along the fault and try to measure stress along it. Then we could look for areas of high stress and create small earthquakes to reduce the potential for a massive destructive earthquake. Although that seems logical, the main problem is that the stress could be handed off to another part of the fault as a consequence, merely moving the threat rather than removing it. In any case, how would we trigger these small earthquakes? We already cause earthquakes (although not on purpose) in areas where we pump fluids into the crust (like Oklahoma), lubricating faults and changing the stress they feel. However, that is done by a Swiss cheese process of drilling rather than targeted drilling into faults -- and right now, we have no idea what the impact of specifically trying to trigger these earthquakes might be. For eruptions, I've heard similar suggestions about drilling to relieve pressure (see the recent spat of articles about Yellowstone caldera). As I've discussed in the past, drilling into a volcano is not likely to trigger an eruption (at least not with our technology) as we just don't have much impact on a magma body ... our drills are too small and the magma body is too large. Even after an eruption, we've tried bombing and blocking lava flows, mostly to little effect on the lava itself. Oh, and we'd never want to nuke a volcano to try to prevent a larger eruption. If a volcano is showing signs of an eruption, nuking it is more likely to trigger a bigger eruption that's also full of radioactive particles, so that would be even worse. The source of magma under volcanoes is tens to hundreds of kilometers underground, so trying to prevent magma from rising in the first place isn't feasible either. In places like the Andes or Japan (subduction zones), magma comes from the melting of the mantle due to the dehydration (loss of water) in the slab of oceanic crust that is being jammed into the mantle. You'd have to stop tectonics to end that. In other places, like the East African Rift, magma is formed by mantle rising and melting, so again, rooted in the deep convection inside the planet. So, what is the point? Much like all geologic disasters, the key to save lives and property isn't stopping the disaster from happening but rather planning so the impacts won't be as consequential to those involved. For earthquakes, it might be strict building codes and early warning systems to help people stay out of harm's way. For volcanoes, it might be preventing people from living too close to active volcanoes or preparing them for evacuations when signs of eruptions appear. Geologic hazards are best handled by planning and mitigation. This takes organizations (usually governments) to handle the logistics and implementation of the plan. We can see what happens when that system breaks down, like what is currently happening in Puerto Rico. This takes an investment from society reaffirming the need to build better more robust infrastructure to withstand the hazard, even if it means spending money now that might not save anyone until 2060. If not, we leave ourselves exposed to increasing damage and death from geologic disasters. We live on an active planet and as residents of the planet, we need to learn to live with that change.

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