The eruption of a volcano can be one of planet’s most destructive events- spewing huge amounts of rock, gas and ash that can kill people, cause crops to fail, disrupt air travel and even alter the weather. But not all eruptions are cataclysmic. Some are a lot quieter and far less deadly. There are many types of volcanoes, but all are cracks in the earth with a chamber of molten rock, or magma, underneath. The hot magma is lighter than the surrounding rock, so it rises. As it does, gas bubbles form increasing pressure. The magma starts to flow, taking the path of least resistance. Once the magma reaches the surface, it’s called lava. If the lava is thin, the gases will bubble out easily and the lava will flow quietly. But, if the lava is thick, the gases will cause it to erupt explosively creating boulders, cinders and ash. Some volcanoes have a collapsed central section called a caldera that can act like a plug. As the magma flows elsewhere, the caldera may sink until it cracks and the magma has a new path to the surface. Then the volcano can literally blow its top.