Teachers should know how volcanoes are formed. They are formed by the collision of plate tectonics. There are 4 different types of volcanoes. There are shield volcanoes which are some what flat and form slowly over time. There are composite volcanoes, also known as stratovolcanoes, which are steep sided and often the most deadly. There are cinder cone volcanoes which are the simplest type of volcano, they have a cone shaped summit which is formed by steam shooting out of the top of its vent and causing cinder to fall around it. The last type of of volcano is a lava dome. Lava dome volcanoes are formed by thick forms of lava too thick to flow any long distances.
Some rocks formed by volcanoes are pumice and obsidian. Pumice is formed when a stratovolcano erupts and the ash cloud mixes with the atmosphere. The mixture of these two components causes a chemical change in the atmosphere. This causes a lightening storm to occur and pumice forms and falls from the sky. The second type of rock formed is obsidian. Obsidian is formed when the lava from an eruption flows into surrounding water and cools off quickly. It cools off so quickly that it turns the lava into a black glass like substance.
Some rocks formed by volcanoes are pumice and obsidian. Pumice is formed when a stratovolcano erupts and the ash cloud mixes with the atmosphere. The mixture of these two components causes a chemical change in the atmosphere. This causes a lightening storm to occur and pumice forms and falls from the sky. The second type of rock formed is obsidian. Obsidian is formed when the lava from an eruption flows into surrounding water and cools off quickly. It cools off so quickly that it turns the lava into a black glass like substance.