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How likely is a major eruption at Cotopaxi? What’s happening inside the volcano? An interview with the director of Ecuador’s Geophysical Institute

This interview with Mario Ruiz, director of Ecuador’s Geophysical Institute, was conducted Friday night by Erika Guarachi of El Comercio in Quito. Since then, there have been several more explosions at the volcano. The Geophysical Institute reported Monday morning that activity within the volcano has not changed significantly since Saturday and that the situation remains dangerous.

What’s happening at the Cotopaxi volcano?

The volcano has been showing anomalies since mid-April but in recent days we had seen a downward trend in activity, both seismic and of gas emissions. This suddenly changed on Thursday afternoon when we observed a swarm of small earthquakes.

Vulcan Cotopaxi
Volcan Cotopaxi

Then, on Friday at 4:02 and 4:07 in the morning, there were two relatively small explosions, but they could be heard in the surrounding area.

What kind of explosions?

According to an analysis of the ash samples, they were of the phreatic type, which means that a rise in temperature in the volcano vent caused water to vaporize and force itself to the surface. It’s similar to what happens when the valve on a pressure cooker is opened. The pressure of the vapor broke through the rocks that cap the molten material in the vent. The ash we are seeing as a result of this is rock pulverized by the force of the escaping vapor.

The other type of explosion is magmatic, in which case the magma itself forces its way through the rock and we have a full eruption.

Were there more explosions?

Yes, other explosions were recorded on Friday at 10:27, 14: 30, 15:35, and at 13:46. (More have occurred since the interview.)

How much ash fell in the surrounding area on Friday?

It was not a heavy ash fall since they were not a huge explosions. Because the steam carried the ash up to eight kilometers in the atmosphere, the ash was distributed over a large area, mostly to the northwest of the crater although some of it went toward the east. It affected parts of southern Quito.

Mario Ruiz, Director of the Geophysical Institute
Mario Ruiz, Director of the Geophysical Institute. Photo credit: El Comercio

What does the emission of ash mean?

Ash occurs because there is fracturing of rock in the volcano, as I said before. The ash is an indication that there is growing pressure inside the vent of the volcano and is an indications that magma is pushing toward the surface.

In the town of Sangolquí and other nearby locations there was the smell of sulfur …

In addition to the steam, the volcano emits sulfur dioxide and hydrogen dioxide. These gases have a strong odor and can be smelled in small amounts when they area dispersed into the atmosphere.

Can you say that the volcano is in eruption process?

It is safe to say that the volcano is showing signs of a phreatic eruption and that this leads to the strong possibility of a magmatic eruption in the coming days, weeks, or months —  sometime in the relatively near future.

What is happening now within the volcano?

Magma is rising within the volcano vent and is beginning to destabilize the material above it. This includes the groundwater, the result of rain- and snowfall, that turns to steam and then causes an explosion. The magma is in the process of establishing a conduit within the vent, allowing it to rise.

Parts of a volcano
Parts of a volcano

Is the glacier on Cotopaxi affected by the explosions?

Yes. Some of the ice inside the crater has cracked and some has melted. But the glacier outside will be affected more by pyroclastic flows, rivers of lava, rocks, gases and hot sand running down the flanks of the mountain. We are watching this carefully.

What are the possible scenarios of the volcanic activity?

There are three scenarios that we are considering. First, that the activity of the volcano will reverse course and gradually decline. Second, that the activity will continue to increase leading to an eruption within days, weeks or months. Third, that an eruption happens immediately, without warning.

Of these scenarios, which is the most likely?

The second scenario, but we may be moving toward the third one.

Why do you believe this?

When we first began to see increased activity at Cotopaxi, we knew we had the possibility of an eruptive event but believed that the volcano would need several more months to come to that point. Volcanoes are complex systems and these determinations are hard to calculate. In terms of gas pressure and earthquakes, we actually had a decline in activity for several days until Thursday. In the broader perspective, we understand that activity has risen considerably over several months, so it was not unexpected that the volcano was building to an eruptive event.

What do you tell people?

The volcano is in a process of that is likely to result in an eruption and citizens must do their part to prepare and, above all, to avoid panic. People must make plans based on reliable information, not on rumors. They should rely on official information issued from this office and by the government, which has access to this information.

How often are reports?

We are now issuing reports every two hours.

How do you know if a major change happens at night?

We are tripling the number of people who monitor the volcano at night. Emergency services are also adding personnel at night.

In the case of an eruption occur, what is the warning time?

In the case of an eruption, we are first concerned about pyroclastic flows but, more important, is development of lahars, which are the result of melting ice. We have developed a system that will give an alert quickly to allow time for mobilization. In the case of lahars, we will have about 12 minutes to send out the warnings. We hope to have the most vulnerable populations out of the danger zone before the lahars arrive.

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Credit: El Comercio, www.elcomercio.com