Rain and the river washed the ash downhill towards the ocean. At the bottom, the sediment of ash clogged up the river, effectively damming it. This resulted in the whole town being flooded with ash-mud called lahar. They literally had to dig themselves out, after the lahar dried. This house shows the level of the ash. Chaitén, Chile.
Photo taken from a car. The driver was driving us all around town looking for bread to buy. We never found any. Well, it was New Year's Day.