In this week’s digest we’re looking at three different things that I like to think of as the rock stars of Earth Science — the things people know about and tend to treat as discrete hazards. And while you can treat volcanoes, earthquakes and hurricanes as separate things, they are all parts of the same Earth system and, as such, are interconnected — and not necessarily in ways you might expect.
Earth and Atmosphere: A Volcano-Hurricane Relationship
I love a piece of research that brings together two apparently different things. This week I came across a study that links large volcanic activity and the occurrence of major hurricanes.
That the two are connected is self-evident. Volcanoes can inject vast quantities of material (aerosols) into the atmosphere and those aerosols can have a significant impact on atmospheric temperatures which, in their turn, are integral in generating hurricanes. The climate impacts of major events, such as the eruptions of Toba in Indonesia, Laki in Iceland and, more recently, Pinatubo in Chile, have had observable climate effects lasting for years.
Up until now the exact nature of the relationship has remained confusing — largely because there are so many other influencing factors that it’s been difficult to separate then out. The research published this week by a team from Lamont-Doherty Earth Observatory and Université du Québec à Montréal used computer modelling to examine the relationship.
The study focuses on volcanoes within the tropics, and its finding were that: “Such eruptions cause a strong asymmetrical hemispheric cooling, either in the NH or SH, which shifts the Intertropical Convergence Zone (ITCZ) southward or northward, respectively”. The impacts were shown to last for up to four years.
The ITCZ is the zone at which air masses from northern and southern hemispheres come together and is an area where many tropical cyclones form. The study demonstrated that by moving this zone, large volcanic eruptions also moved the areas where strong tropical cyclones are likely to hit, although they didn’t appear to have an impact on the overall frequency.
By understanding how, and over what timescale, these changes occur, it’s possible to make preparations for an increased likelihood of storm activity in certain areas for some years after a major eruption — and by preparing, save both lives and property.
Detecting Volcanic Emissions from Space
Following up from the item above, I came across a report this week on detecting volcanic emissions from space. It isn’t a newly-published item though it’s relatively recent (dating from October 2018) and I wasn’t able to track down the original piece of research so this piece relies on an article in Scientific American.
It’s worth reporting, however, because it links in to the article above in that it’s about volcanic material in the atmosphere, although its focus is very much on the immediate impact upon human activity, specifically aviation, rather than the climate impacts — although as we saw above, ash from large eruptions has climate impacts as well.
The work uses satellite data to measure the emission of sulphur dioxide, a volcanic gas. The resultant data allows scientists to keep track of activity on some of the most remote volcanoes — something that’s crucial because many volcanos are a long way from habitation, are largely unmonitored yet, while they cause little or no impact to human in the immediate area, are capable of regional or national impacts in terms of aviation.
“Monitoring these events, which often spew ash that can trigger engine failure in airplanes, can help scientists quickly pinpoint potentially dangerous airspace,” reports SA, going on to note that the availability of data is currently limited but its extension could go a long way to reducing disruption to aviation on the future.
The South Sandwich Islands: Earthquakes and Volcanoes
Unless you follow earthquake blogs and feeds, you’re unlikely to have noticed any reporting of two large earthquakes in the South Sandwich Islands. Both of them registered at M6.5, which puts them right up there in the top ten largest earthquakes so for in 2019.
The tremors, though large, were remote and occurred a few hundred kilometres apart, both at intermediate depth (48km and 58km). They occurred along a short (in global terms) section of subduction zone where the South American plate descends beneath the eastern edge of the Scotia microplate, a slab of crust which lies between the South American and Antarctic plates.
Subduction zones are related to volcanoes, and as I’m talking about links between parts of the Earth system it seemed to me that this would be a good opportunity to explain that link. As a slab of crust descends, it heats up and with this heat and increasing pressure, the rock begins to melt. Being hot, it is more buoyant, and rises to the surface, where it erupts.
Subduction zones, therefore, are invariably associated with both earthquakes and volcanoes (although obviously both are found elsewhere). The South Sandwich Islands, remote and generally un-noticed, are an example of this, with eight volcanoes (though none is currently erupting).
It’s also worth noting that if these volcanoes were to erupt, they might have significant potential impact on air travel and, therefore, benefit from the type of monitoring described above.