One of the world’s oldest national parks, Mount Rainier became part of the federal ... one of the world’s most active volcanoes. The Sicily, Italy, volcano is almost constantly in a state ...

This story appears in the May 2019 issue of National Geographic magazine. Washington’s Mount Rainier boasts the largest collection of glaciers on a single peak in the contiguous United States.

It shows the underground plumbing system that provides molten and partly molten rock to the magma chamber beneath the Mount Rainier volcano in Washington state. The scale at left is miles depth.