volcano

Volcanoes are usually located where tectonic plates meet. This is especially true for the Pacific Ring of Fire, an area around the Pacific Ocean where over 75% of the volcanoes on Earth are found. The word volcano originally comes from the name of the Roman god of fire, Vulcan. Volcanos are formed when magma from within the earths upper mantle works its way to the surface. Common volcanic gases include water vapor, carbon dioxide,  sulfur dioxide, hydrogen chloride, hydrogen fluoride and hydrogen sulphide. Volcanoes can be active (regular activity), dormant (recent  historical activity but now quiet) or extinct (no activity in historical times  and unlikely to erupt again). While these terms are useful, scientists are more  likely to describe volcanoes by characteristics such a how they formed, how  they erupt and what their shape is. Most people think of volcanoes as large cone shaped  mountains but that is just one type, others feature wide plateaus, fissure  vents (cracks were lava emerges) and bulging dome shapes.