Geo-Joint: Volcan Paricutin

Farmers know their fate is tied to the natural cycles of rain, heat, cold, and insect invasion. They know their soil type limits the crops they can hope to grow, and that birds and varmints may take a bite out of their harvest. Nature is a kind of frenemy, but there are rules a farmer can expect to operate within—until nature goes rogue. That’s what happened to Dionisio Pulido, a Mexican farmer living near the village of Paricutin, about 200 miles west of Mexico City.

He was out burning some cut brush on February 20, 1943, when he noticed a small hillock in a cornfield was swelling, and a crack about two feet deep was forming in it. It wasn’t the first sign that the earth was getting restless. Booming sounds had been heard around town for weeks despite a lack of clouds or lightning. Still, the farmer wasn’t overly concerned until the ground began to shake and boom, and the fissure started hissing and sending smoke and ash into the air, stinking of sulphur. The ground pushed up seven or eight feet, and the crack widened to several feet. Dionisio panicked for a minute but then moved fast to set his oxen free of their harnesses and to try to locate his wife and sons. They were nowhere to be found, so he got on his horse and lit out for town. Happily, he found them there, where they had run, thinking he must surely have been killed by the earth’s explosion.

Volcan Paricutin in 1943, still building.

A day and a half later, the material coming out of the ground had built up over 150 feet high, and what is called a Strombolian volcano was well underway. This type of volcano is named for the island of Stromboli, Italy, which formed and is still growing by the ejection of basaltic ash, lapilli, and lava bombs. In these volcanoes, abundant gas bubbles aggregate into a large bubble called a gas slug. This gas pushes up the throat of the volcano under pressure, and bursts explosively at the surface, spewing its associated lava out into the air. The lava in this kind of volcano is dry and viscous, or sticky, which also contributes to the explosive nature of Strombolian eruptions. One form of rock this lava turns into as it cools is scoria, which has a very porous construction, and is blown out of a vent in small pieces called lapilli, or as lava bombs. Lava bombs are bigger, football-shaped structures that fly out of the vent and trail off tails on either side of the main chunk as they arc through the air. By definition, they have to be at least 2.5 inches across, but they may football-sized, or larger. They cool and harden before they hit the ground, so they maintain their somewhat aerodynamic shape when they land in the more gravel-like lapilli and ash. Unlike those that produce more runny lava, Strombolian volcanoes are usually cone-shaped heaps of loose material called cinder cones, though they may have lava streams as well.

San Juan Parangaricutiro—only the church was able to keep its head above the lava and ash.

Volcanologists had long studied Stromboli, as it had been erupting for hundreds of years, more or less continuously. It has been called the Lighthouse of the Mediterranean, glowing and sparking for generations of sailors passing its location near Sicily, close to the toe of Italy’s boot. That regularity is one of the characteristics of the Strombolian-type volcano. But at Paricutin, for the first time, such a volcano was observed from its inception. Volcan Paricutin, as it came to be known, grew quickly and stood nearly 330 feet high within a week. The explosive nature of the new vent produced clouds of smoke and ash that reached a few miles in height during March, 1943. In June, lava began to flow toward the village, and the villagers left. Within a few months, a larger town, San Juan Parangaricutiro, also cleared out its inhabitants, and a year later both settlements were mostly covered in ash and lava. Only San Juan’s tall church steeple poked above the new volcanic landscape. The news of Paricutin spread around the world, and many of the early photos of it were made into postcards sent far and wide. The eruption drew attention not only from the scientific community, but also as a tourism highlight that continues today. Most of Paricutin’s production occurred during its first year, when it attained a height of 1,100 feet. Output dwindled for the next eight years, but during its last six months Paricutin put on a show of explosive blasts. Still, by 1952, when all activity stopped, it had only grown an additional 290 feet, covering 10 square mlles in all. While not a major volcano, scientists had been able to monitor its origin, life, and death—a unique opportunity.

Volcan Paricutin made a good showing, but won’t grow any larger.

Paricutin is part of a monogenetic field, an area of eruptive activity that is short-lived and of limited lava supply. It results from the complex interaction of small tectonic plates subducting under the North American Plate on which Mexico sits. The Michoacan-Guanajuato field in which Paricutin is located has about 1,400 vents. For lack of high lava volume, vents in the area don’t become well established, and each batch of magma moving toward the surface makes its own pathway. Paricutin has likely had its day and is not expected to revive itself. For all the attention it drew during its life—many came to witness it, and airflights would change course to give passengers a view—it was not a killer. Though its slow-moving lava buried two towns, no one lost their life to the hot rock. Sadly, however, there were three fatalities from lightning strikes generated by eruptive clouds. And, of course, there was the loss of Dionisio Pulido’s and his neighbors’ farmland under tons of volcanic rock. At least Dionisio’s name lives on as one of the very few people to have witnessed the actual birth of a volcano.


 

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PHOTO CREDITS:

Volcan Paricutin in 1943, still building.
Source: Wikimedia Commons: K. Segerstrom, USGS (Public domain)
San Juan Parangaricutiro—only the church was able to keep its head above the lava and ash.
Source: Flickr: sharloch (CC by SA 2.0)
Volcan Paricutin made a good showing, but won’t grow any larger.
Source: Wikimedia Commons: Jim Luhr, Smithsonian Institution (Public domain)

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