Measuring and Assessing volcanic activity
There is a range of ways volcanic activity can be measured.
How do we measure the size of an eruption?
The Volcanic Explosivity Index (see table below) is the volcanic equivalent to the Richter Scale. The VEI is used to identify the magnitude of a volcanic eruption. The VEI is based on the height of the ash plume and an estimate of the volume of material that is expelled. Eruptions with small VEI numbers are far more common than those with a high VEI. Strombolian eruptions usually have a VEI of 1 or 2 whereas Plinian eruptions have a VEI of 5 or 6.