And always La Palma...

Hello !

This Sunday, October 24 at 16:53 UTC, there were exactly 400 earthquakes in CSEM-EMSC database for the last twenty-four hours in the world.

Half of them (precisly 200) had occurred in the Canary Islands region.

And earthquakes “swarm” is always ongoing.



but the picture is very different if you apply ‘magnitude filters’. The global M>4 map that I check regularly doesn’t often get so impacted by swarms, although plate boundary swarms do happen sometimes (Mexico most recently) and can lead to 2-3 times more M>4 in a day than ‘normal’. Never gets into the 100s though (thankfully I would say!).
I did notice a deep M4.7 magnitude quake in the Canaries the other day, that seems different enough from typical volcano swarm quakes - does it mean something is happening in the deep magma source for the current eruption?
So much information hiding in those quake records and maps!

Hello @DAC

For the last month, for the depths, the average is 13,98 km, with maximum of 49 km (ML 4.5) and minimum of 2 km.

For magnitudes, we have an average of 2,88 with maximum at ML4,7 (three times at 1x38 and 2x40 km)


But we all know that in seismology the figures are treacherous … and we make them say what we want … “despite” 2700 records involved in those statistics…



Nice chart Louis, really does look like there is separation between the shallow and deeper seismic activities, very tempting to think that there is a deeper magma chamber feeding a shallower one beneath the eruption? I am further tempted to ‘see’ that the largest earthquakes are the deeper ones, but don’t know why that should be? Presume 40+km is well below the Moho for oceanic plate like in the Canaries, whereas the shallower focused quakes would be well within the crustal plate.
Seisimic data isn’t really treacherous, it just doesn’t like to give secrets away easily?!
Thanks again for taking the time to produce the fascinating graph.
Best regards Dave

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In this case, you can augment seismology data with petrological data from actually looking at the rocks. Mineral grains that equilibrate at 35-odd km are likely to have somewhat different chemistry to grains that crystallize (from the same fluid phase) at 10 km. You also typically see grains of different sizes from the postulated different magma chambers.
I don’t recall if my department’s teaching collection had any rocks from the Canaries - any of the island group - but one of the professors who taught “Ign Pet” had a thing for cumulate “igneous sediments” form Greenland, while the other had many specimens from volcanos of the Tonga- Vanuatu group (one of which went “bang” recently) - very different tectonic situations to the “intra-plate” volcanism of the Canaries. But the principles of petrology would still give a lot of information about the growth histories of the phenocrysts (large crystals) of the rock, and by inference the ascent history of the rock.

I spent a week pottering around Tenerife on a volcanology holiday a few years back, and remember much discussion on such matters, But it was a holiday, without exams (though the “spot the sector collapse” after dinner game using sonar imagery was fun!) so I didn’t really commit any of the data to memory.

I wouldn’t bet more than the price of one beer on the different islands of the Canaries group having similar substructures and plumbing.

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There was a lot of activity (sorry) on the INVOLCAN FB page, they were sampling just about everything they could lay their hands on at the time. Presume they are busy writing it all up now that things have gone quiet! I agree, if there is a two stage plumbing system then there is a possibility for phenocrysts / cumulates to form in the deeper chamber - although not sure how long they need to form - if there is a quick flow through and eruption, maybe we only get fine grained basalts (and ash)? Most of the eruptive activity at the end was ash, which would likely result in little or no preserved texture and could even alter mineralogy - hydrating and carbonating? Most of the accompanying gas emissions were CO2 I think (some ongoing)? I would love to get out to the Canaries and see for myself! Sorry seem to have strayed far from seismo :wink:

I can’t remember Canaries petrology that well - we certainly looked at a good number of hand specimens and thin sections in college, and I did a week’s volcanology there on a OU-alongside trip a few years back. But most of the memory is gone now.
Single phase phenocryst growth is not unknown - some olivine-basalts from the “Tertiary Volcanic District” I recall being particularly fine, sometimes even idiomorphic, and there are the classic leucitite-phyric volcanics of Vesuvius - but it’s not the norm. Maybe because I had one professor who worked with Wager on the cumulates of the Skaergaard, and another professor who got hot under the collar for the zoning and compositional change in the placioclase-to-anorthosite flotation-cumulates samples they’d brought back from Greenland and almost ignored … but maybe I just saw too much zonation and multiphase history in those intrusions. From the other samples I saw though, I do get the feeling that simple magma-chamber histories (and by implication, eruption histories) are the exception not the norm.
Dragging slightly back in the direction of seismo, I saw a report recently that another cycle of inflation has been recorded in the volume inflated to the SW of Reykjavik, suggesting that they may be lined up for another summer of midnight sun and lava glow.
Quick check on Iceland’s earthquakes-and-volcanism page (I also use their weather forecasts ; if next week’s storms are important to you, worth keeping the site in your “favourites” list) and navigating to the Reykjanes Peninsula … that looks to me as if the playground has moved closer to Keflavik. The main airport. Joy and bliss are unbounded.