Q COSTA RICA – Photographs taken by a drone, some 300 meters over the active crater of the Turrialba volcano, allowed volcanologists for the first time look inside the colossus.

What was learned is that the active crater’s inner walls exhibit slopes that exceed 55 degrees of inclination and the mouth of the volcano is 126 meters ( 413 feet) deep. To put that in perspective, it is 1.5 times the Banco Nacional building in San Jose (which measures 83 meters high).

The crater measures 69,000 square meters ( 742,000 square feet), for example, covers an area a little larger than the National Stadium.

Not only that, at the bottom, there is an internal crater from where volcanic materials such as ash, pyroclasts (fragments of magma) and gases are emitted, that measures 189 meters wide

In fact, thanks to the Digital Elevation Model or DEM generated from images taken by the drone, researchers were able to calculate the volume of material that would fit in that hole: 2.3 million cubic meters, the equivalent of 165,000 truck loads.

According to Paulo Ruiz, a geologist at the National Laboratory of Materials and Structural Models (Lanamme) at the University of Costa Rica (UCR), the erupted material so far has been old, but if the 2.3 million cubil meters had been juvenile material, we would be at the first level of the explosive index.

Ruiz said the flyovers were done in March 2016, “just before the eruptions of April and May of that year, which changed the volcanic system.”

Digital model of elevation (DME) of the active crater of Turrialba volcano to March 2016. (Courtesy of Lanamme)

Ruiz added that to define the date and flight plan for the drone, weather and seismic activity had to be monitored so that “there were no earthquakes.”

The images taken were processed at the Lanamme laboratory using the Agisoft 3D modeling and mapping software.

“Our DEMs will be very useful in understanding how craters form during eruptions,” Ruiz said.

Thanks to this model, the researchers observed that the gap that opened on the side wall of the southwest (active) crater in 2010 when it began eruptive activity, generated a terrace 60 meters long, 35 meters wide and 81 meters deep

“The other thing we have seen is that the central (non-active) crater has been filling up because the ash (from the active crater) is falling there, fill by the runoff,” said the geologist.

“If we were to fly again, I’m sure we would see a lot of changes that happened from year to year,” said Ruiz, who clarified that this is the goal and this year they have not yet flown over the crater because volcano activity has not permitted it.

Sources: La Nacion; Lanamme