Parts of the system have been partially buried by thin volcanic debris.

Obsidian and other volcanic debris have been found in the area.

This ash and other volcanic debris, are believed to have come from the park area itself.

The water usually comes from two sources: rainfall or the melting of snow and ice by hot volcanic debris.

At that time, sand and volcanic debris settled into an ancient ocean.

The building was covered in ash and surrounded by volcanic debris, but its occupants survived.

The authorities are worried that recent heavy rains could cause landslides of volcanic debris.

"Are you afraid they were trapped in the volcanic debris?"

A lost city is discovered on the island of Thera, buried under volcanic debris.

Another 9 people are missing and presumed buried under volcanic debris.