Volcanoes

Volcanoes can be harmful to life and property. Several events caused from volacanoes can be very hazardous.

• Pyroclastic Flows are a mixture of hot gases and rock fragments that move rapidly with gravity. These currents can be highly destructive.
• Lahars look like a wet slurry of cement. They are made up of rock fragments mixed with water. They rush downslope picking up anything in its path, from vegetation to buildings. Some of the load eventually gets deposited thus slowly decreasing its size.
• Lava Flows are molten rock streams that pour from an erupting vent or just trickle out. These flows will destroy everything in its path but generally dont move very fast.
• Ashfall/Tephra is produced from explosive eruptions. Rock fragments are produced when rock or magma is ejected with an explosion. Ash fallout can damage buildings, water, transportation and can also have an impact on human health.
• Volcanic Gas are gases that are released into the atmosphere during an eruption. As gases are taken away they react with water to form poisonous acids. These acids can destroy vegetation and also metal. Volcanic gases smell bad and can also cause animal and human fatalities.

Supervolcano

Supervolcano is the popular term for a large volcano that usually has a large caldera and can potentially produce devastation on an enormous, sometimes continental, scale. Such eruptions would be able to cause severe cooling of global temperatures for many years afterwards because of the huge volumes of sulfur and ash erupted. They are the most dangerous type of volcano. A supervolcano is capable of producing a volcanic eruption with ejecta greater than 1,000 cubic kilometers (240 cubic miles). This is thousands of times larger than most historic volcanic eruptions.

Volcanologists and geologists do not refer to "supervolcanoes" in their scientific work, since this is a blanket term that can be applied to a number of different geological conditions. Since 2000, however, the term has been used by professionals when presenting to the public. The term megacaldera is sometimes used for calderas with supervolcano characteristics, such as the Blake River Megacaldera Complex in the Abitibi greenstone belt of Ontario and Quebec, Canada. Eruptions that rate VEI 8 are termed "super eruptions".

Supervolcanoes occur when magma in the Earth rises into the crust from a hotspot but is unable to break through the crust. Pressure builds in a large and growing magma pool until the crust is unable to contain the pressure. This kind of eruption is typically sufficient to cause a long-lasting change to weather (such as the triggering of an ice age) sufficient to threaten the extinction of species, and cover huge areas with lava and ash.

Though there is no well-defined minimum explosive size for a supervolcano, there are at least two types of volcanic eruptions that have been identified as supervolcanoes: large igneous provinces and massive eruptions. Although there are only a handful of Quaternary supervolcanoes, supervolcanic eruptions typically cover huge areas with lava and volcanic ash and cause a long-lasting change to weather (such as the triggering of a small ice age) sufficient to threaten species with extinction.