Within the space of three days, high levels of activity have prompted the National Risk Management Secretariat to raise the danger levels of the Tungurahua and Reventador volcanoes from yellow to orange, the second highest alert level. A red alert signals extreme danger to population areas.
Ecuador’s Geophysical Institute (IG) says that the risk level for Cotopaxi remains yellow, although they say internal pressure continues to build and that they expect an eruption.
Tungurahua, 120 kilometers south of Quito and 40 kilometers east of Ambato, has been expelling lava and large rocks since last weekend, but the main concern has been the heavy volcanic ashfall to the west of of the 5,020-meter-high volcano. According to area farmers, the ash has caused millions of dollars of crop loses and is threatening livestock by coating forage. In Ambato, schools were closed on Thursday due to ashfall that accumulated to as much as three inches.
Tungurahua began its current eruptive cycle in 1999 and poses the most serious threat to the city of Baños, a tourist destination with a population of 25,000. In 1999, the city was ordered evacuated but residents forced their way back into town and the government has not attempted an evacuation since. Geologists say that Baños is built on lava flows from previous eruptions and that it would probably be destroyed in the case of a major eruption.
The 3,560-meter Reventador, is located about 90 kilometers east of Quito in the jungle and has been active since 2002. Unlike Cotopaxi and Tungurahua, it located in a wilderness area and poses little threat to human populations, although it blanketed Quito with an inch-deep layer of ash in 2003.
Meanwhile, IG geologists say that the threat from Cotopaxi remains high and say they worry that residents nearby the volcanco will let their guard down due to the lack of change in recent activity. Activity has remained moderate for more than two months, with a constant expulsion of gas, steam and ash from the 19,800-foot crater.
Retired volcanologist George Lassister called the simultaneous activity in three volcanoes alarming. “This is almost unprecedented and presents a very scary scenario,” he says. “If we have major eruptions of both Tungurahua and Cotopaxi close together, it would overwhelm rescue and recovery efforts. I shudder to think about it.”
“Cotopaxi is far more dangerous in terms of potential eruptive strength than Tungurahua, but Tungurahua’s location above Baños creates the most concern,” he says. “The magma chamber under Cotopaxi is 200 to 300 times larger.”
Lassiter said that Cuenca is unlikely to be affected by a major Tungurahua eruption although a light ashfall is possible.