Why do we have different types of volcanoes?

Since the material coming out of the Earth’s core is different in different areas, the resultant changes are also different. If the magma is very hot, more than 1000°C, it is dark, thin and mostly flows quietly. The sides of such volcanoes have gradual slopes. Colder, and hence more viscous, magma often erupts in explosions. The volcanic cone is steeper. Because of the heat in the Earth’s core, geysers (water fountains), solfataras (discharge of hot sulfuric gases), and hot water sources are found near the volcano. These are often used for heating in places such as Iceland.