A number of factors determine the severity of damage caused by a volcano or an earthquake:
The type of plate boundary that has caused the volcano - destructive plate boundaries cause violent volcanoes.
The proximity of a volcano or an earthquake's epicentre to a large settlement - those situated near large cities where population is dense cause more deaths than those in less populated areas.
The proximity of an earthquake's focus to the earth's surface - the closer the focus the more powerful the earthquake.
The wealth of the country in which it erupts - a developed country can afford scientific prediction instruments, buildings that are designed to withstand earthquakes, a quick reaction force and good medical care for the injured.
The time of day when the earthquake strikes - if it strikes when people are congregated in one area, for example, at rush hour, its results can be more devastating.Â