For the last couple weeks Mexico’s Popocatépetl volcano has been sporadically leaking out some ash, but on Monday it gave up a huge shockwave.

The Mexican publication the Informador (via Google Translate) reported Monday that villages near the crater and even southeastern Mexico City were put on alert for ashfall by the National Center for Disaster Prevention.

The Ministry of the Interior put the eruption column at more than four miles high and spewing ash bits little more than a mile away.

volcano eruption

(Image: YouTube screenshot)

volcano eruption

(Image: YouTube screenshot)

volcano eruption

(Image: YouTube screenshot)

volcano eruption

(Image: YouTube screenshot)

Small fires were caused by some of the ash flying to fields nearby, but the volcano returned to lower activity levels after the event.

Wired’s Eruptions blog described some of the science behind the blast:

Volcanism at Mexico’s Popocatépetl is highly punctuated, especially during its current level of activity where domes of lava grow in the summit crater. These domes occasionally collapse or are destroyed by explosions that can lessen the pressure on the magma beneath to create an even larger explosion. This is akin to popping the top off a shaken bottle of soda — the dissolved bubbles come out of solution rapidly as the pressure is released and you get an explosion of soda.

[...]

You can see how pulsatory the eruption is as well, with the dark plume churning like steam from a steam engine. This might be due to new magma rising in the conduit, feeding the eruption as it continues. However, even with all this fury, the volcano went back to looking idyllic with only some minor puffs of ash within two hours after the explosion (see below) and only the grey ash on the slopes to show for the seemingly giant explosion. Even as impressive as that explosion seems, these ash and tephra deposits usually are wiped clean out of much of the geologic record by rains as they are only a few centimeters thick near the volcano and millimeters thick further away.

Mexicos Popocatepetl Volcano Erupts Sending Miles of Ash Into Sky

The volcano also erupted on May 20. (Photo: ARTURO ANDRADE/AFP/Getty Images)

Check out the footage of the most recent eruption from one of the web cams that monitors the volcano (Note: It’s sped up so the event could have lasted up to 20 minutes, according to Wired):

In other volcano news, a video from almost a year ago has begun gaining traction. Why? Maybe because it shows a man running up a lava flow.

YouTuber Marc Szeglat wrote that it’s a “lava art craft worker” who is running up Mount Etna, an active volcano in  Sicily. The worker apparently is “very experienced and knew what he was doing.”

Check it out:

Wired’s Eruption blog too took on this video and explained how the worker was able to run on the molten rock:

Taking a look at the video, the lava flow in question is moving pretty slow and has a dark crust on it. This means it is likely pretty cool — in fact, it looks like it is a`a lava, which is even more viscous than the pahoehoe many people associate with lava flows. Crust forms quickly on lava flows because there is a high temperature gradient between the lava (at ~1000°C) and the air (~25ºC), so the lava hardens into a semi-flexible crust. Based on where the guys are standing, the lava flow isn’t likely very large because the guy who doesn’t run up the flow doesn’t seem concerned to be standing only a few feet away. The flow itself looks confined to a small channel surrounded by solidified lava. My guess is that this little flow is fairly far from the vent (source).

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Now, I’m not sure why he chose this route to get up the ridge (well, beyond showing off), but if that flow has a decent crust (which it does) and is moving fairly slow (which it is), and if you move quickly, your weight isn’t going to be enough to cause you to sink into the flow. The big caveat here is that if the crust is uneven and you hit a thinner part, you could find yourself with more lava on your boot that you’d like (that is, more than “no lava”) or worse, trip and stick your hand on the flow surface that is still likely very hot when you fall. From the looks of the video, the guy took five, maybe six, steps on the flow and was back up on solid lava by the time he reached that next level and stopped.

“This isn’t to say you should ever do what this guy did. Don’t. There are many things you could do and survive but shouldn’t because there are very high probabilities that you’ll get hurt. This guy beat the odds,” Wired’s Erik Klemetti wrote.

(H/T: io9, Smithsonian Magazine)