Three explosions within six minutes propelled a thick plume of ash and volcanic gas 900 meters into the air above Arenal Volcano on the afternoon of Nov. 2. The blasts triggered a hot pyroclastic flow down the western flank of the peak that evoked oohs and ahhs from tourists in volcano lookouts, but didn’t cause any reported damage.
Strong winds swept the ash clouds southeast and fooled some eyewitnesses into thinking the flow took that course as well. Eliécer Duarte, volcanologist with the Universidad Nacional’s Volcanological and Seismological Observatory (OVSICORI), inspected the flow the following day, saying it “looked like a river of dry materials that made an alley during the avalanche.”
Only the small size of the flow staved off disaster. Thirty-six hotels, hot spring resorts, trails and lookouts are within 5.5 kilometers of the volcano’s peak, a danger zone that could be consumed in lava within five minutes of a powerful eruption, according to a report by Robert Tilling, volcanologist with the U.S. Geological Survey (TT, March 12, 2004). He was invited in December 2003 to study the potential for disaster, and his recommendations have been part of an ongoing community awareness and political action campaign by the National Emergency Commission (CNE).
There is only minimal risk to tourists who stay in that area to observe the volcano, OVSICORI’s Duarte said. When Arenal erupted, “There were people in the lookout who saw the spectacle and enjoyed it.”
“It doesn’t seem dangerous to me (as long as) people obey the off-limits zones; in fact, it’s a very educational, creative experience that teaches people about the fresh materials that surge from the internal layer of the earth,” he said.
The volcano has been active since 1968, gurgling up large eruptions an average of twice a year and constantly dribbling lava flows around its peak that draw droves of spectators to watch it glow on clear nights. The explosions were the culmination of a period of heightened activity during the past two months, OVSICORI reported in a statement, though none of the previous activity was as dramatic.
