The document discusses different types of volcanoes. It explains that volcanoes are mountains that usually erupt gas, ash, and molten rock. Inside volcanoes is hot magma, which becomes lava when it reaches the surface. Some volcanoes are active and always erupting, while others are dormant or extinct. The document provides examples of specific volcanoes like Mount Vesuvius, which destroyed Pompeii in 79 AD, and Mount St. Helens, which killed 57 people during its 1980 eruption. It also briefly describes volcanoes like Teide, Etna, Nevado de Ruiz, and Krakatoa.