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Volcanowatch

July 23, 2009

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


Explosions and lava flows continue from Guatemala's volcano trio

An ash plume rises from the Santiaguito lava dome at Santa Maria volcano in western Guatemala.  The volcano erupts ash plumes such as this every half hour to two hours.  Santa Maria is one of three volcanoes erupting in Guatemala this week.
An ash plume rises from the Santiaguito lava dome at Santa Maria volcano in western Guatemala. The volcano erupts ash plumes such as this every half hour to two hours. Santa Maria is one of three volcanoes erupting in Guatemala this week.

When asked by a journalist why he robbed banks, the famous 1930s bank robber Willie Sutton (no relation to HVO scientist Jeff Sutton) was reported to have simply said, "Because that's where the money is."

It can be said that the same "Sutton's Law" principle guides volcano researchers around the globe. To better understand volcanic activity and hazards, it makes sense to go "where the eruptions are." This reasoning was a primary motivation in Thomas Jaggar's founding of the Hawaiian Volcano Observatory at the edge of Kilauea's summit caldera. Numerous "Volcano Watch" articles, as well as a large body of volcanic process research, have already illustrated how much we have learned here.

But to understand the full spectrum of volcanic behaviors around the globe, scientists need to find other persistently active volcanoes to serve as "natural laboratories." One country that has a trio of highly active volcanoes and features an assortment of fascinating eruptive behaviors is Guatemala.

Guatemala, although a relatively small country, hosts 22 volcanoes that have been active over the past 10,000 years, and three of these—Santa Maria, Fuego and Pacaya—happen to be erupting this week.

Santa Maria volcano, located in the western portion of the country near the city of Quetzaltenango, is noted for its frequent explosive eruptions and growing lava dome. For decades, ash-laden plumes have been erupting from its lava dome every 0.5-2 hours. At the same time, a towering, unstable, and viscous lava dome (called Santiaguito) extrudes from the vent and slowly migrates downslope. A volcano with simultaneous effusive and explosive behavior is special, and one which has exhibited such activity for decades is truly remarkable.

This activity was set in motion by Santa Maria's colossal 1902 eruption, which rates as one of the largest of the 20th century. Much of the south flank of the stratovolcano collapsed in the explosion, and at least 5,000 people died.

Fuego volcano, closer to the center of the country and overlooking the city of Antigua, is much less predictable. This stratovolcano commonly shifts from phases of quiet effusion of lava flows down the steep flanks into periods of window-rattling, incandescent explosions. The almost constant change could provide valuable insights into how volcanoes, in general, can make such dangerous transitions.

Pacaya volcano, visible from Guatemala City, is probably the most benign of the three. It is typified by very small explosions of incandescent spatter, largely confined to the summit crater, with occasional periods of short lava flows. Its frequent, and relatively safe, eruptive activity makes it a popular tourist destination, as well as a good location for close-up scientific observations of small-scale explosive activity.

The frequent eruptive activity at these three volcanoes poses hazards, in the form of volcanic mudflows (lahars), block and ash flows, and ashfall, to local villages and nearby large cities. Keeping an eye on these volcanoes is Guatemala's equivalent to the USGS, called INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia). This agency installs and maintains seismometers and other monitoring equipment and operates observatories at the base of Santa Maria and Fuego for direct observations.

International volcano research in Guatemala is currently picking up. Safe access to the volcanoes was hampered by the Guatemalan Civil War, which ran from 1960 to 1996. Like Willie Sutton's bank robbing vocation, international research on active volcanoes includes both obvious and unanticipated hazards.

Conditions in Central America have improved markedly, but even today, scientists rely on armed guards when traveling into the field to protect against robbery. Hazards aside, though, there are numerous researchers, including several from U.S. universities, such as Michigan Tech and New Mexico Tech, who make regular trips to Guatemala's volcanoes to install instruments, collect data, and work with local scientists there. And, as Willie Sutton did, they accept the risks that go with the potential rewards.

Kīlauea Activity Update

Surface flows were inactive early this week, due to the July 19 DI event, but resumed on July 22 with active breakouts on the pali. At the coast, the Waikupanaha ocean entry has resumed after the DI event, but the Kupapa`u ocean entry remains inactive.

The vent at Kīlauea's summit was dark and quiet all week, producing only a very small quantity of rock dust from small collapses of the vent walls. Volcanic gas emissions have increased over the past week and are currently similar to levels prior to June 30, resulting in high concentrations of sulfur dioxide downwind.

No earthquakes beneath Hawai`i Island were reported felt this past week.

Visit our Web site (http://hvo.wr.usgs.gov) for detailed Kīlauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kīlauea activity summary; email questions to askHVO@usgs.gov.

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Updated: July 29, 2009 (pnf)