Voices: Volcanoes everywhere ... is there a link?

by Jessica Ball
Friday, January 20, 2012

It may seem that there has been an unusual amount of volcanic activity lately, with major eruptions occurring in Iceland, Guatemala and Ecuador. But is it really unusual, and are the eruptions connected?

The short answer to both questions is no.

At any one time, there are numerous volcanoes erupting in the world — the Smithsonian Global Volcanism Program lists 17 on any given day in their most recent report. These volcanoes are located in a variety of tectonic settings, from hot spots to subduction zones, and they are all erupting for different reasons. But the eruptions are almost never related, even if the volcanoes are geographically close to each other.

For the people in Guatemala and Ecuador, the past few days have brought not only volcanic eruptions, but a tropical storm to boot. Aside from happening at the same time, the eruption of Guatemala’s Pacaya has no relationship to the eruption at Ecuador’s Tungurahua — the volcanoes are located on two different continents and on two separate tectonic plates. The same is true of most earthquakes, although there has been some research into the possibility that large earthquakes can trigger other earthquakes.

Here’s a closer look at the two most recent eruptions.

Pacaya volcano, Guatemala

On Thursday, May 27, the Pacaya volcano in southwestern Guatemala started erupting violently, raining lava and ash on Guatemala City and other nearby towns. Pacaya is a 2,500 meter-high basaltic volcano about 30 km south of Guatemala’s capital city, and its MacKenney cone has been erupting almost constantly since 1965. In the past decade, however, eruptive activity has been limited to lava flows on the southwest flank of the volcano, punctuated by relatively small Strombolian bursts and fumarolic degassing — vents emitting steam and gases — from the summit crater of the MacKenney Cone.

Strombolian eruptions occur when large gas bubbles rise through magma and then burst when they reach the top of the magma column; as the gas bubbles “pop,” they throw clots of lava and ash into the air. Ash columns from this type of eruption generally rise no more than a few kilometers above the volcano. Thursday’s eruption, however, was much more violent than usual. Large sustained explosions threw tephra (ash and rocks) up to a thousand meters into the air, and dropped tons of ash on nearby towns and Guatemala City.

This tephra poses major hazards: volcanic bombs (molten rocks) and glassy, air-pocketed scoria can cause serious injury. A news reporter, Anibal Archila, was killed on Thursday night when he was struck by volcanic bombs; several other people from local villages were also killed in the same manner. In addition, the heavy ash has caused roofs to collapse, which could cause even more fatalities and injuries. More than 2,000 people in villages near Pacaya have been evacuated, Guatemala’s international airport was shut down and the area was declared to be in a state of emergency.

The arrival of Tropical Storm Agatha from the Pacific a few days later did nothing but worsen the effects of Pacaya’s eruption, creating large lahars and widespread flooding. (A lahar is a mudslide that incorporates volcanic material; much of the Pacific coast of Guatemala is covered by volcanic deposits.) Agatha dumped more than a meter of rain on Guatemala and other parts of Central America, killing at least 132 people and prompting the evacuation of nearly 100,000 more as mudslides and flooding threatened their homes. (Meanwhile, the intense rains ate away at the thick deposits of pumice fill, the remnants of old volcanic ash flows, beneath Guatemala City — prompting the opening of a 90-meter-deep hole, called a piping feature, right in the center of the city.)

Tungurahua volcano, Ecuador

In Ecuador, the 5,000-meter-high Tungurahua stratovolcano also erupted on Thursday. Strong (Plinian, or Vesuvius-type) explosions sent ash clouds soaring more than 10 kilometers above the volcano’s summit, and produced pyroclastic flows that threatened villages around the base of the volcano. Tungurahua mainly erupts andesitic and dacitic lava, which is more viscous than Pacaya’s basaltic lava, and creates even more explosive eruptions. The volcano is located 150 kilometers southeast of Ecuador’s capital of Quito, and although there are fewer people near it than near Pacaya, eruptions have destroyed villages and displaced thousands of inhabitants as recently as 2006. The ash plume created by the current eruption shut down the nearby Guayaquil airport and suspended flights between Quito and Lima, Peru.

Tungurahua has often experienced this kind of violent eruption. Its last major cycle of activity lasted from October 1999 to July 2009, and produced pyroclastic flows, lava flows, lahars and Plinian eruption columns. The volcano is especially prone to flank collapses and lahars, due to its steep slopes and numerous drainage channels; lahars often wash out roads and bridges that are needed for the evacuations that have occurred often in the past decade. Tens of thousands of people live in towns and villages around the volcano, and the city of Baños, which sits in a narrow valley 9 kilometers to the northeast of Tungurahua’s summit, is particularly at risk from pyroclastic flows, lahars and falling ash.

Are the eruptions linked?

Only by coincidence. What does happen is that a large eruption or earthquake will cause media outlets to pay more attention to geologic disasters for a time. The eruptions and earthquakes have been happening all along, but don’t always make the news; when they do, it only seems like there is more volcanic or tectonic activity. The eruption of Eyafyallajökull in Iceland has drawn attention to ash-laden volcanic eruptions because of the huge disruption it caused in worldwide air traffic. (Eyafyallajökull and nearby Katla volcano are a special case where their eruptions have historically been linked.)

Had the eruption at Eyjafjallajökull not occurred, there probably would have been less interest in the eruptions in Guatemala and Ecuador. In addition, many eruptions (and earthquakes) occur in remote areas or third-world countries, which are rarely given much attention by major news outlets — so we simply don’t hear about them.

The lack of science reporting on geologic activity in developing countries is a shame, because volcanic eruptions in places like Guatemala and Ecuador have the potential to cause terrible damage; the effects of tropical storms and hurricanes (which are sadly common at this time of year) can only make it worse.

Pacaya’s ash and the precipitation from Tropical Storm Agatha have not only damaged people’s homes and businesses, and shut down the country’s major airport, they have also threatened much of Guatemala’s coffee crop. The loss of one of their main exports would be a devastating blow to the already poor country. In the area of Ecuador where Tungurahua is located, people who depend on tourism and agriculture to make their living will also suffer from the stratovolcano’s eruptions. There is no easy way to recover from the effects of a volcanic eruption — or any natural disaster — without labor and financial resources that neither country can easily afford.

My own research has taken me to Guatemala, where I’ve received enormous support from INSIVUMEH, the organization which is responsible for monitoring and researching volcanic, seismic and hydrologic events. This is an enormous task; Guatemala has 22 volcanoes that have erupted in the last 10,000 years, three that are currently active, and every year the country experiences many earthquakes and floods. INSIVUMEH is still a fairly small operation with limited personnel and funding, and although they have dedicated and skilled scientists, they have difficulty simply keeping up with monitoring. The combination of Pacaya’s eruption and the flooding and lahars from Agatha is surely taxing their capabilities, and I can only hope that my friends in Guatemala will be able to recover quickly from these disasters.

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