Peru volcano: Do growing rumblings point to a big eruption to come?

The most active volcano in Peru is living up to its explosive reputation.

Ubinas volcano has been rumbling and occasionally venting gas over the past six months, but on Monday it erupted a 1,000-foot pillar of ash. In addition, a dome of red-hot lava has welled up over the past week, reaching almost 400 feet across, completely filling the pit left by the explosions in 2006, during the volcano's last active period.

The lava glows even in daylight, suggesting very high temperatures within.

Monday's eruption was the first explosion since February 14, but the volcano has been emitting plumes of steam, sulfur dioxide, and occasional ash for months.

On March 25, residents of the nearby towns of Querapi and Ubinas reported light ash falls and strong rumbling noises. 

The volcano is experiencing over 200 earthquakes a day, according to a detailed report released on Sunday, pointing to the churning and rising magma within the volcano.

In their report, a team of experts recommended the immediate evacuation of Querapi, a small town about three miles south of Ubinas, and improvements to the roads throughout the area to allow for a wider evacuation. Authorities have since relocated the 50-odd residents of Querapi and are considering evacuating the town of Ubinas, a few miles further from the volcano.

The new report marks a shift in tone from a March 25 announcement, when geophysicist Orlando Macedo, a leader of the science team, told local news source RPP that the gentle degassing posed no threat to residents, though he did point out that the massive quantities of sulfur dioxide being released by the volcano could harm people with breathing problems.

Dr. Macedo is part of the Arequipa Volcano Observatory of Peru's Geophysical Institute (OVI-IGP), who along with scientists from The Geological Mining and Metallurgical Institute (INGEMMET) have been monitoring Ubinas volcano for weeks.

A month ago, the volcano was releasing 1,000 tons of sulfur dioxide per day, the new report says, and as the magma rises, more and more gases are being released. By the end of March, the volcano was belching over 3,000 tons per day, peaking at 4,009 tons of poisonous gas on March 22. 

The rising magma – evidenced by the bulging dome of lava at the surface, the increasing frequency of small earthquakes, and the huge and growing volume of sulfur dioxide gas – points to a major eruption to come, but just how large remains a mystery.

Ubinas volcano's explosive history

Ubinas volcano's biggest historical eruption came about 1,000 years ago, when it released a towering column of ash, steam, and gases that left a 10-inch-thick layer of ash as far as 25 miles away. In the past 500 years, Ubinas has erupted at least 24 times, usually in the form of steam bursts, gas plumes, and ash clouds, according to an article in the current issue of the Journal of Volcanology and Geothermal Activity. Ash and steam may sound less dangerous than lava, but some of the most dramatic volcanoes in history have been of this type, from Mount Saint Helens to Krakatoa.

Ubinas lay quiet for about 40 years after an eruption in June 1969, then awoke with a bang in May 2006. It erupted fairly steadily for the next three years before quieting down again. Its latest round of activity began in August 2013, when a few faint ash plumes presaged a string of six explosive eruptions between September 1-3, 2013. The first, and biggest, of the six, shook the earth for over an hour, belched ash and smoke a mile into the air, and flung boulders measuring up to six feet across, according to the Smithsonian Institute's Global Volcanism Program. Local news reported that Querapi residents fled their homes to gather in the town square.

Since its September rumblings, Ubinas has limited its eruptive activity to occasional puffs of ash, water vapor, and gases, some only observed by pilots and others large enough to be seen by satellite. In addition, earthquakes have shaken the volcano's flanks, suggesting the churning and rising of magma within.

In early March, a team of volcanologists from Peru's Geophysical Institute (IGP) reported seeing a glowing body lava reaching over 100 feet long. By March 25, authorities were conducting evacuation drills with schoolchildren and were taking steps to permanently relocate the town of Querapi.

You can watch up-to-date timelapse webcam footage from Ubinas volcano at VolcanoDiscovery.com.