Most of the population in this region lives in river valleys. A river valley is a low land between mountains that has a river flowing through it.
The flooding was caused by the collapse of a section of a glacier. The collapse caused a landslide [sudden movement of soil or rock from higher ground to lower ground]. The landslide was so powerful that, at first, scientists believed it was an earthquake. It caused a powerful wave of ice, water, mud, and rocks.
Photo Credit: Nick Fox/Alamy Stock Photo
