These vents are called volcanoes. The best known volcanoes are the cone shaped type with a hole in the top such as Mount Fuji in Japan , Mount Vesuvius in Italy and Mount St. Helen s in the United States. Volcanoes act as vents because they permit the steam, gases and pressure to escape into the atmosphere. However, sometimes, the pressure and gasses build up and explode forth in a volcanic eruption that throws rocks and gas and dust miles into the sky. They also sometimes erupt in molten lava, which is melted rock, that burns everything in its path.
Volcanoes are very dangerous because they are so powerful and filled with fire and gas.
Today, volcanoes continue to erupt causing much damage, injury and even death. Volcanologists are scientists who study volcanoes and try to predict whether an eruption is going to occur and, if so, when. Their predictions may save many lives. They also catalog the various volcanoes and study them to learn about what goes on beneath the surface of the earth. In the Philippine Islands is a volcano named Mount Pinatubo.