The general term used by volcanologists for fragments of volcanic rock and lava of any size expelled from a volcano. Tsunamis are also referred to as tidal waves, but they have no relation to tides. Volcanic explosivity index is a scale from 1 to 8 measuring of the size of eruptions. See also Volcano World's How Big are Eruptions . Opening in Earth's crust through which volcano expels ash, other volcanic products and gases.
Thick liquids have high viscosity, thin liquids have low viscosity.
A vent in Earth's crust through which molten or hot rock, steam, and ash reach the surface, including the cone built by the eruptions. Gases may also escape continuously from volcanic vents, fumaroles, and hotsprings. See the USGS for more information on volcanic gases . Scientists who study volcanoes. The name comes from Vulcano, one of the Aeolian Islands north of Sicily, believed to be the home of the Roman god of fire, Vulcan.