#Popo2016: the mule diaries | Volcanology

We have only spent a few days in Mexico, but so much has happened already: we have driven 600 km around the flanks of El Popo whilst getting a comprehensive crash course in Mexican music by Hugo; we have casually named previously unmapped lava flows; scared away scorpions with our merciless hammering on rocks; digested 3-cows-worth of Mexican food; and, above all, marveled at snow-covered Popo, which was silent witness and patron of all our endeavours.

Photo showing the snow covered, smouldering volcano
A snow-covered Popocatépetl (aka El Popo) as seen from Paso de Cortes on 5 March

But let’s wind back a bit and take it up at the beginning of our trip, Mexico City…

A brutal Moloch, a sensation of petrol and corn, a symphony of jack-hammers and out-of-tune street organs, a place where everything is huge, a place that makes London seem a refuge of peace.

For instance, the UNAM University has 300,000 students – rather a city in its own right than a campus – and on our way there (we are meeting Hugo and Guillem to discuss our strategy for the fieldwork) our taxi driver gets dauntingly lost.

Photo showing the three volcanologists seated with maps and PC on a table in front of them, discussing places to go.
Chiara (middle), Hugo (right) and Guillem (left) discussing the main targets for this year’s field season

The drive from Mexico City to Amecameca, where we will stay during the fieldwork, usually takes two to three hours. Although we have hardly spent more than two days in Mexico City, we can’t wait to get out of there.

Even our brand new pick-up truck is revving in pleasant anticipation as we leave from UNAM – maybe there is some overexcitement involved, but we don’t even make it 1 km before we collide a little bit with a taxi. Just a little bit, really, but enough to keep us stuck for another three hours of Mexican bureaucracy. Feelings run high temporarily, but the cold, clear night in Amecameca cools us down again.


Our first mission of the fieldwork brings us to the north east flank of the volcano. After the hectic pace in Mexico City, the tranquility of this region is balm for the soul. About 1,500 years ago, Popo’s last large-volume lava flow, Nealticán, ploughed the landscape here.

The Aztecs began mining this lava stream soon afterwards; they used the rocks to craft molcajetes (if you don’t know what this quintessential culinary tool actually is, may I refer you to this archived blog entry from 2015). Before the industrial revolution, this area was quite wealthy thanks to the exploitation of the lava flow, as can be seen by the dominant church in Xalitzintla.

Photo showing the village close by at the bottom, with the volcano in the distance dominating top half.
Popocatépetl towering over the village of Xalitzintla, which means ‘River of ash.’ The massive Nealticán lava stream covering an older lava flow can be seen.

Today, however, not much money can be made with quarrying the Nealticán lava – one truckload of rocks is only worth 500 pesos, which is about £20. Yet, almost the entire front of the lava stream is being quarried by the locals. It is a wasteful, dangerous job: with tools that are probably almost identical to the ones the Aztecs used – a variety of chisels and hammers – they excavate the lava stream piece by piece.

At many places, crosses commemorate those who died under a pile of destabilized lava. When Guillem expresses his astonishment about how these people are so cold-bloodedly working under overhanging rock cliffs, Hugo says: it’s not cold blood, it’s necessity that makes them do it.

Photo showing a dirt track leading to an open rock face shrouded in boulders and stones from the quarrying process
A quarry at the Nealticán lava flow, mined by local workers


Photo showing tools and wheelbarrow resting up against a rock face
The miner’s tools of their trade.

However, with the help of the miners, we finish our first hard-rock task in no time, and we move on now to more dirty business. That’s right, we are targeting the pumices of Popo’s explosive eruptions next – these are very light, glassy pieces of lava that form when there is a lot of gas in the lava, which makes the eruption very strong and explosive.

Single lava pieces can be hurled tens of kilometers high into the air before they fall back towards the ground again. This so-called pumice is full of the former gas bubbles, which makes them swim on water. Oh, and they are also full of dust.

Here is one of the exciting discoveries we have made so far: you can see 4 different units in this pumice fall, which are created by pulsating changes in the intensity of the eruption.

Photo showing a hammer resting up against a pumice wall for scale, exhibiting 4 obvious strata.
A pumice fall with 4 subunits. These deposits are created during very strong eruptions, during which lava is hurled high up into the air before falling back to earth again.

And where this comes from, there is much more to discover! …Ok, I promise, I won’t be writing only about pumice. So don’t be afraid to pop by this blog again soon – hasta pronto!

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