In My Humble Opinion:
It would be very difficult even today to accurately account for deaths due to earthquakes and much less so to those caused by Volcanos. There are
three phases in each but with EQ it is very short, thus the question will be which levels of death do one count.
Earthquake you have a large number deaths directly because of the quake - buildings collapse, rock slides, tsunami, etc. Following that original
event, there are deaths due to displacement and exposure to environment like cold weather, rain, snow, etc. This might stretch into months. Lastly
you have - in major quakes at major centres - the long term deaths due to disease, water pollution and malnutrition.
On the other hand with Volcanic eruptions you have those deaths directly as result of the eruption i.e. Pompei, Merapi, etc. Relatively these are low
compared to EQ for the very valid reasons Putterman points out. Then there are the short term outfalls usually still linked to the volcano; gas
poisoning, famine due to crop failures, etc. This might stretch to distance even out of sight from the volcano. Until now I think if we compare EQ
and volcano - then EQ's lead the pack as human killer.
But larger volcanic eruption has the tendency to affect the whole world. There are Meteorological changes which will plague people for months or
even a years afterwards. This past few months we have seen tremendous changes in weather patterns all over the world - in particular very severe
flooding around Equator regions. I will dare to state much of these are due to large volumes of volcanic ash in high atmosphere and in particular the
high volume of Sulphur that was blown by Chile and Nabro volcano's. These can stay in 'orbit' for a year or more and the Sulphur does have a
immediate effect on cloud forming.
The first result is high rainfall - floods.
The second result is cold temperature and low sunshine - crop failures, famine and even reduction in marine life.
Another less obvious result due to ashy and cloudy sky is the reduction in solar radiation most important: Ultra Violet. UV light (radiation) has the
benefit to humans that it kills most bacteria and viruses. If we look back in history to the major disease outbreaks there is somewhat of a strange
coincidence; usually there were in periods following major volcanic eruptions. By those eruptions I mean those of volcano's that placed large amounts
of ash and
sulphur in the sky. Off the thumb I would say about 1/3 of big eruptions.
The end result: If we do count the long term deaths due to meteorological changes; then Volcano's will win the race by far.
Sorry for such a long post again!
To sum up:
EQ's has relative short violent effect of few minutes, maybe a few sessions with after shocks.
After a few months things usually settles down and people go on with living.
EQ affects local area only; unless there are major Tsunami!
Volcano's is long life - often months and sometimes years; all that time it is blowing ash and other poinsonous gases like Sulphur Dioxide into the
sky. Wind picks it up and can even take it all around the world. Volcano's affects large geographic areas; even as much as a ribbon all around the
world; in some historical cases - the Whole World.
After such major eruption settles down, the after effects can last for many years.
edit on 24/10/2011 by Aromaz because: (no reason given)