How does ash from a volcano destroy stuff?

Answer 1

There are a number of ways. In many explosive eruptions produce clouds of ash, rock, and gas called pyroclastic flows that race down the sides of a volcano at great speed. The force alone can be incredibly destructive. Additionally, these flows are extremely hot. Some are so hot that, upon settling, the ash is welded together and cools to form a solid rock. Ash that falls from the sky can weigh down on rooftops, especially if it absorbs rainwater, and can cause buildings to collapse. In some cases ash can mix with water either from rain or from snow and ice melted by an eruption to form mudflows called lahars. These mudflows look like muddy water when they move, but have about the same density as concrete.