Eruptions have been picking up steam since late November on the 16,479-foot-high (5,023-meter-high) volcano, which towers above the town of Baños—popular with tourists for its thermal baths and scenery. Some 25,000 residents live permanently in high-risk evacuation areas under the mountain's steep flanks.
"When ash falls, it's a headache," Wunderman said. "It doesn't melt like snow, and it doesn't run downhill right away like rain. It sits and waits for a storm or some unusual event, and then it all comes down at once as mud.
"That can change the [shapes] of the valleys, and a location that was a safe distance above a stream can suddenly end up in the stream."
Tungurahua volcano, seen above from the town of Runtun, spews incandescent rocks and lava on Sunday. The mountain is among the most unsettled in volcanically active Ecuador.
Tungurahua eruptions have threatened nearby communities several times, including a major event during World War I (1916 to 1918). That eruption was the most recent serious activity until the current long-term eruption began in 1999.
The initial 1999 eruption quickly melted a small glacier that had formed on Tungurahua's peak. Baños and other communities were evacuated in October 1999, but by the next summer most people had returned, and the town was back in business as a tourist hub.
Intermittent eruptions have continued over the past decade and caused half a dozen deaths in 2006, when entire villages were buried with scorching rock and ash.
Tungurahua, pictured on November 30, is known as "throat of fire" in the local Quechua language. Despite the volcano's active history and uncertain future, not all those who live in the mountain's shadow are especially concerned.
"Volcanologists working in the area tell me that many locals are a bit blasé about the volcano," Wunderman said.
Lava pouring from Tungurahua's peak—pictured on November 28—is the result of tectonic forces far underground.
"Here the plate associated with the Pacific Ocean goes under the Andes," Wunderman said. "That can cause earthquakes 375 miles (600 kilometers) inside the Earth."
Volcanic disturbances have become rather commonplace in the Tungurahua area in recent years, with explosions and ash columns occurring each year. The road to Baños, for example, is occasionally closed by ash.
"The fact is that it's one of the world's great smoking guns, in terms of a large town in proximity to a very dangerous volcano," Wunderman said.