A volcanic eruption includes very large energy discharges on the surface of the Earth. Outbreaks involving always are very large masses in motion, often explosions and always high temperatures that are frequently above 1000oC. Therefore, volcanic eruptions are associated with violent changes in the state of affairs in our environment, and sometimes they are directly to the detriment of human beings. Volcanic eruptions also have the potential for climate change. Volcanic eruptions range from the outflow of only millions of M3 magma (molten stones) up to unimaginable thousands of km3. How volcanic eruptions can proceed and their cause is linked to both fundamental processes deep in our planet, as by the local geological structure of the outer parts of the Earth, as well as the interaction between the very warm magma and the external environment.