Volcano

• Each volcano has certain characteristics, although there are a number of types of volcano found throughout the world. A volcano can have a crater, which is a steep-sided depression at the summit of the volcano. A major eruption often leaves a volcano with a characteristic called a caldera, which is a steep depression at the summit of the volcano. A volcano can be equipped with a single vent extending deep within the ground through which magma is ejected. In some cases where a series of volcanoes are found, such as in Hawaii, the volcanoes can be connected by a series of vents leading to a single large vent through which magma is passed to the series of volcanoes.
  
  

Temperature

• The ferocity of a volcanic eruption can be affected by a series of factors, including the temperature at which the magma is ejected by a volcano. The higher the temperature at which the magma is ejected leads to a less violent eruption, according to Spokane Falls Community College. The hotter the temperatures produced by a volcano, the less pressure and resistance are felt by the magma as it is ejected by the volcano. Where cool temperatures accompany the lava being ejected, the magma can be thicker and build up more pressure than the thinner, hotter forms of lava.
  
  

Gas

• Gases form in the production of magma and affect the level of violence caused by the eruption. When magma is ejected from a volcano, a certain amount of pressure must build before the eruption takes place. One of the most important factors in the eruption of a volcano is the silica content, with higher levels of silica creating a more vicious eruption. Other gases that build in the magma as it moves towards the surface of the volcano are nitrogen, sulfur, chlorine, hydrogen and argon.
  
  

Lava

• The type of lava created by the mixture of temperature and gases within the lava flow affects the violence of an eruption. For example, pahoehoe and Aa lava flow create less violent eruptions, while lava known as rhyolite produces a more violent eruption.