1.4 The Volcanic Explosivity Index is a scale used to measure the size of explosive eruptions.

The Volcanic Explosivity Index (VEI) is a scale used to measure the size of explosive eruptions. Volume of erupted material, size of the ash cloud and qualitative observations are used to determine where an eruption falls on the scale. The scale is logarithmic, meaning a VEI 2 eruption is ten times more powerful than a VEI 1 eruption.

The VEI runs from 0 (non-explosive eruption) to 8 (supervolcanic eruption.)

Previous: 1.3 A volcano is formed when magma reaches the Earth's surface

See: 1.4a A volcano that has had an eruption of VEI 8 is known as a supervolcano for more on VEI 8 eruptions