Scientists 'shook' Mount St. Helens to find the massive magma reservoir hiding beneath our feet.

In 2014, scientists set off 23 explosions and deployed 3,500 seismographs around Mount St Helens; the experiment helped image a magma reservoir roughly 4 to 15 km beneath the volcano. Researchers used these artificial waves to map the complex underground plumbing system, showing how molten material hides deep inside the mountain.