Boqueron/San Salvador

The national capital of El Salvador stretches up onto the flanks of active San Salvador Volcano.  (Image:  Rick Wunderman, Smithsonian Institution)

The national capital of El Salvador stretches up onto the flanks of an active volcano. (Image: Rick Wunderman, Smithsonian Institution)

We looked at Ilopango Caldera last time, but experts say that another nearby fire mountain – the explosive San Salvador volcanic complex in El Salvador’s capital city – is one of the most dangerous volcanoes in Central America.

Many people outside the region just think of Central America in terms of a land bridge between North America, Mexico, and South America. However, powerful and complex geological forces are also in play there.

Nowhere is this more apparent than in El Salvador – a country about the size of the US state of Massachusetts that contains at least twenty active volcanoes.

These volcanoes are part of an eruptive front across western Central America that even geologists call “impressive.” Plate tectonic movements are very complex here, but in general El Salvadoran volcanoes result from the subduction of the Cocos tectonic plate underneath the Caribbean plate.

Millions at risk today

People have lived on and around the San Salvador complex for thousands of years. The place names they have given the area aren’t always comprehensible to outsiders. For example, the Nahuat people dwelling there at the time of the conquistadors in the sixteenth century, called it Kozkatlan, “The Place of the Diamond Jewels,” although the area today is not known as a source of gemstones. In fact, the land there is composed of tephra from multiple explosive eruptions.

The name of the modern active vent at San Salvador is Boqueron. Per Wikipedia, it means “Big Mouth,” but per a machine translator it means “anchovy” (not “swordfish“). Whatever the meaning, Boqueron had a VEI 4 eruption around a thousand years ago, per the Smithonsonian’s Global Volcanism Program, and in 1917 it had a VEI 3 eruption that was preceded by a powerful earthquake that damaged the city of San Salvador:
 


 

Today the volcano is actually part of the San Salvador metropolitan district. Boqueron, the summit vent, sits half a mile (1 km) above and a little over 4 miles (7 km) away from downtown. This is an ideal situation for deadly pyroclastic flows and lahars. Incredibly, farmers even live inside Boqueron and grow crops along its upper edges.
 

Image:  MARN

Image: MARN


 

There are many hazards from this volcanic complex. Even a small eruption there would cause severe physical, social, and economic disruption; larger ones the size of Boqueron’s known historic events would cause huge death tolls and directly or indirectly devastate the entire country.

Preparing for the next emergency

Fortunately, monitoring today shows that the San Salvador volcanic complex is quiet (Spanish language). What should be done when it begins to stir again?

Since 2009, El Salvador has had (Spanish language) a National Plan for Emergencies. This helps, and so does the country’s volcano monitoring program. The city of San Salvador is protected as well as possible, but there are still practical limits to evacuating over two million people.

Few eruptions can be predicted, either. Sometimes volcanoes start waking up, and after weeks or months, go back to sleep without erupting. If volcanologists and emergency teams call an evacuation and then an eruption doesn’t happen, people will be less likely to evacuate the next time around, when the volcano might actually go off. At other times, volcanoes give very short notice before even major eruptions. In such an event, no big metropolitan area can be cleared in a day, let alone a few hours or minutes.

Truly, given its explosive history and the presence of over two million people living on its flanks and in its crater, the San Salvador volcanic complex is one of the most hazardous places in the whole region.



Categories: Sunday morning volcano

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