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Earth sciences news

5 Posts tagged with the geology tag
1

A team of geologists from the Museum and Imperial College are in Mexico carrying out  fieldwork at two of the most active volcanoes in the world: Popocatépetl (Popo) and Colima. Catch up with their adventures in this series of blogposts.

 

This uncomfortably oblique photograph marks the end of this year’s fieldwork at Popo. As you can see, we have been extraordinarily successful in collecting samples:

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All in all, we have collected twelve boxes full of pumice and lava in the last two weeks, each of them weighing about 20 kg!

 

Moreover, not only have we been doing well in bagging rocks, but we also made many important field observations, such as the relation of the different volcanic units in time and space. This is essential for the proper handling and analysis of our samples.

 

As soon as our heavy load arrives at the Natural History Museum, I will crush the rocks into tiny pieces and examine them using different types of microscopes. We are confident that this will tell us intriguing stories about how Popo works. The adventure has just begun!

 

But first, we will drive this trunkful of rocks to Mexico City, where we will also say ‘muchissimas gracias’ and ‘hasta luego’ to Julie, who will fly back to London, and also to Hugo and Guillem, who will stay in Mexico City. Chiara and me will stay in Mexico for another week, which we will mostly spend in Colima. There, about 500km West of Popo, the ‘Fuego de Colima’ volcano is currently very active, with several small eruptions every day. We are excited to go there and see some nice ashclouds, and of course, we will keep you posted about our ventures in West Mexico!

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A team of geologists from the Museum and Imperial College are in Mexico carrying out  fieldwork at two of the most active volcanoes in the world: Popocatépetl (Popo) and Colima. Catch up with their adventures in this series of blogposts.

 

After our dirty but successful pumice-rich first week at Popocatépetl, we were all happy to get that dust off our shoulders and start chasing the various lava flows that make up most of the volcano edifice. Now, if the whole volcano is built by lava flows, it should be really easy to find these rocks, shouldn’t it? The short answer is: no. The longer, picturesque answer will take you into the wild, rough and bumpy world of Popo’s lower flanks, where a good rock is as hard to find as a sleeping baby lion in the vast African savannah. Join us on the magical ROCK SAFARI!

 

Early in the morning, when Popo is still entangled by the night’s misty claws, we make our way from the hotel in Amecameca towards the south-eastern flank of Popo, the land of the sneaky rocks.

 

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Somewhere down there they are hiding: the Popocatepetl lava flows!

 

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On the lookout for rocks: moving in this terrain makes you reconsider what you may call a ‘road’.

 

What makes it so difficult to find these lava flows is the fact that most of them are buried by a thick cover of the Popo pumices (not again!) and lahar deposits. So in many cases the only thing we can find on top of these dirty deposits are loose boulders of rock, which we can’t even be sure belong to the place we find them lying. A tedious job requiring lots of caution!

 

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An easy catch: can you spot the rock?

 

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Julie finds a rock that has tried to hide away from our hammers…

 

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…we took care of it.

 

Such a seek-and-destroy campaign can easily take a couple of hours for one lava flow and is not necessarily successful. However difficult it may be, when you finally spot a nondescript, lichen-covered rock specimen, the adrenaline you feel while smashing it into pieces to see what species it is pays off generously.

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Another boulder from a Popo lava flow successfully tracked down.

 

One factor that contributes to our (otherwise rather questionable) sense of adventurism during this rock safari is the daily recurrence of a group of local forest watchdogs roaming around the terrain. The first time they came, they only surrounded our car with a grim look on their faces, checking if we were hunters (if they could only know!).

 

The second time, they had machetes (they were cleaning the roads from vegetation) and we had to give them some money so they’d let us pass. The third time, it was already getting dark, and they had shotguns to guard a road against any people with mischief in mind. We certainly didn’t at this point. The good thing is that by now they know us and they greet us cheerfully every time we pass them.

 

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Obviously, we weren’t keen on photographing the shotgun watchdogs, so instead we present evidence that some lava flows are not good at hiding away. This the Nealticán lava flow, which is the most recent of Popocatépetl’s lava flows (in geological terms, ‘recent’ means younger than 2,000 years). Because of its young age, it is not covered by a lot of deposits and is thus widely exposed. Unfortunately, this flow is the exception to the rule.

 

In this manner, we have chased down a couple of lava flows in the past few days. We are very happy with the outcome of our rock safari and can’t wait to introduce these samples to their new temporary habitat while they are shipped to the UK: cardboard boxes!

1

A team of geologists from the Museum and Imperial College are in Mexico carrying out  fieldwork at two of the most active volcanoes in the world: Popocatépetl (Popo) and Colima. Catch up with their adventures in this series of blogposts.

 

Time flies – we've already been here for a whole week! While Popo was smoking and steaming like a champion, we dived deeply into the dirty, dark side of geology during this week: We sampled ash and pumice from the four large eruptions of the last 15,000 years. For hard-rock geologists like Chiara, Julie and me, this was a challenging task. So much dust, so few proper minerals! But if you want to understand how Popo works, this is simply what you need to go through.

 

Armed with shovels of various sizes, a tape measure, our geological hammers (you never know!), and, last but not least, a hoe (romantically referred to as the ‘mano de gato’ - ‘the hand of the cat’), we went out onto Popo’s flanks to search and exploit its volcanic deposits. Hugo, the Popo expert, unerringly navigated us to the top spots, where we then got to work. The following series of pictures reveals what this actually involved:

 

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First of all, we need to get an overview about what we see. In this case, we are looking at the deposits of at least three large eruptions of the last 5,000 years. If you want to know more about such eruptions, just ask us!

 

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Next, we describe the different layers we see. This includes the size and properties of the clasts, the structures, and the thicknesses of the units.

 

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After that, we can start sampling. Sometimes it can be straightforward, sometimes you may need a helping mano de gato (‘the hand of the cat’) to clear the sampling site and guarantee a neat sample.

 

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Some or all parts of the layers might be covered with soil or debris. In this case, the shovels of various sizes come into play. This picture demonstrates that in doing so you may excavate more than rocks, such as the rubbish of what apparently was a big Mexican Fiesta (including diapers and mayonnaise).

 

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On other occasions, it might not be garbage, but a proper treasure that you dig out: A volcanic bomb! Hard-rock geologists, get your hammers and cameras ready!

 

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And this is what you get if you repeat the above steps for a whole week.

 

Now, this might have all been a bit nerdy, so I’ll finish this blog entry with an almost completely unrelated note. Of course we are not only interested in rocks, but also in Mexican culture. Naturally, when a worker in a quarry (we were there by chance, obviously) told us that there was a man in the nearby town San Nicolás de los Ranchos who would craft wonderful molcajetes (pestle and mortars), we went there immediately.

 

On the way there, Hugo explained to us that molcajetes are mortars especially designed for making salsa. Did I mention that they are made of rock? This is also why the salsa made using molcajetes tastes different than if you just use a simple blender – the sauce takes up the taste of the rock.

 

With this salsa-lesson learned, we were all quite keen to see these wonderful items. But how would we find the Molcajete Man in the village? It’s easier than you’d think: you just ask anyone on the street for molcajetes. He/she won’t be able to give you a helpful answer, but 3 minutes later the whole village will know about the lost tourists looking for molcajetes. Out of nowhere, a random girl will appear next to your car, offering to bring you to Molcajete Man. Being a lost tourist, you accept the offer and follow the girl for about 30 minutes through the village, which gives you the opportunity to take some tourist pictures:

 

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San Nicolás de los Ranchos is built on laharic deposits from Popocatépetl.

 

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Evacuation routes are signposted all around Popo.

 

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The presence of the volcano inspires local artists to draw their own conclusions on what happens in nature.

 

Finally, we reached the mansion of Molcajete Man. He looked different than I expected, but obviously he is a master of molcajeting.

 

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Molcajete Man crafting a molcajete.

 

We would have really loved to get our own molcajete by that time, but these mortars are just way too big to transport to the UK. At least they are if you are already sending a garage full of pumice there.

 

Thus our pumice week has ended, and we enter phase two: rocks! I can already promise you it will be an exciting ride, so visit us again!

3

We are delighted to welcome you to our Popocatépetl blog, which for the next three weeks will be fed with facts, anecdotes, pictures and maybe even videos of our fieldwork at two of the currently most active volcanoes in the world: Popocatépetl (henceforth: Popo) and Colima (henceforth: Colima).

 

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Our very first view on Popo, at dawn in Amecameca. Not yet convinced? Scroll down and prepare to be amazed!

 

But first things first: introductions. Our team includes Chiara, volcano-addicted petrologist at the Museum, Julie, passionate geochemist and lecturer at Imperial College, and me (Martin), their new PhD student. I'll be focusing all my energy on Popo in the coming years.

 

Together, we're setting out to shed light on what makes Popo erupt, a poorly understood yet very important issue, since there are more than 30 million people living around Popo – that’s about half the population of the UK! By analysing the rocks and crystals that Popo has erupted in the last 23,000 years, Chiara, Julie and myself are trying to find out more about how Popo works, which will hopefully help in forecasting future eruptions and keeping the people living there safe.

 

But to do all this, we first need rocks – a lot of rocks! And that’s exactly why we are in Mexico right now. Together with our local colleagues, Hugo and Guillem, we will spend our days at the volcano, looking for the freshest rocks around and putting them into plastic bags. As Popo is quite active in the moment, this is a quite exciting and dangerous task!

 

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Popo is in a steamy mood these days.

 

But before we dive into excitement and danger with you, we want to give you an idea of our experiences during the last 48 hours. We started in London Heathrow (25.3m above sea level) on Sunday night, arrived in Mexico City twelve hours later, went straight up to Paso de Cortes (3,400m a.s.l) to get a close grasp of Popo, then had a decent rest in our hotel in Amecameca, just to get up again at 5.30 the next morning for a 10-hour day of die-hard pumice sampling at almost 4,000m a.s.l.

 

Now we are a bit tired – so we thought we would give you and us an easy start with some Popo pictures, taken all around the volcano. You will surely agree that Popo is in good shape, and a truly admirable volcano – ‘a proper strat’, as Julie put it musically.

 

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Popo as seen from Paso de Cortes - preparing for the big bang?

 

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Volcanic eruptions are not the only danger lurking at Popo's flanks. Luckily Julie knows no fear and chases away the feral cow.

 

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After the cow-shock we seek comfort in some good old volcano stratigraphy!

 

If you want to know what Popo does next, how we deal with the thin air and the cows, and how fashionably we collect both hard and soft rocks, we urge you to come back here. Also, don’t be afraid to leave comments, questions, and general thoughts about volcanoes.

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We arrived on Tuesday, set up what will be our home for the week, with a stream babbling under.

 

We spent today visiting fossil shops and talking to the owners to see what was on offer and meet the collectors. We then went to the Lyme Regis Museum to talk to our colleagues there about new specimens and the local geology. Whilst there Emma had some fun dressing up as Mary Anning, the 'Princess of Palaeontology'.

 

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Emma dressed as Mary Anning with a newly acquired Ichthyosaur skull.

 

In the afternoon (after an ice cream by the sea) we set off for Seatown where we learnt about the geology and did a little fieldwork. The geology is the upper Lower Lias (about 185 Million years ago) - it is a marine setting with lots of belemnites and ammonites.

 

We found lots of bits of belemnite, but the highlight was definitely finding a phragmocone of a belemnite; the cone-shaped structure that housed the creature's internal organs. Of the ammonites, Aegeroceras was the most common find. However we did find part of an Amaltheus (My favourite Jurassic ammonite because of its rope-like keel).

 

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Seatown in the glorious sunshine.

 

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One of the many ammonites (Aegeroceras) we found

 

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Emma and Zoe in the field at Seatown.

 

Tomorrow we are heading off to a secondary school event in Dorchester to explain the wonders of cephalopod taxonomy. Now we are heading off to grab some well earned dinner! Come back to read more about our adventure!