17. Volcano Ruiz, Colombia
The volcano is known for the unusual structure of the magma that flows out of it. It consists of pyroclastic substances and water, which makes it more fluid. In 1595, after the lava flew into the river Guali and Lagunillas, more than 635 people died. After the incident repeated in 1845 – another 1,000 people died. Despite this, people have built a village on the mountain, which was buried under another deadly hot lava flow in 1985 that took the lives of 23,000 people!