The world endured a record number of disasters in 2000. There were about  850 natural disasters last year compared to about 750 in 1999. However,  largely because of the earthquake in Turkey in August of 1999, there were  approximately 75,000 fatalities in 1999 compared to about 10,000 this past  year. Volcanic eruptions typically account for a fair share of disasters in  any given calendar year. Worldwide in 2000, the eruption of Mt. Usu in  Japan was one of the big news-makers, and in North America, the December  eruption of Popacatepetl or "Popo" as it's referred to by the locals, was  the biggest of the past year.

Popo and the nearby Iztacihuatl loom above the Anahuac Valley in central  Mexico, one of the most picturesque landscapes in the world. Popo is  Mexico's largest volcano, and at about 17,900 feet, it's the second tallest  in North America. Its eruption on December 18 was preceded by several  years of yawning and stretching. From late November through mid December  there were several weeks of trembling and rumbling, and finally, streams of  lava poured down its flanks, and clouds of ash billowed out of its top. The  ash fell on Mexico City, 40 to the southeast. Fortunately, thus far there  have only been a handful of eruption-related deaths.

The series of eruptions last month was certainly the most violent of the  past 100 years and possibly even the last 1,200 years! Popo seems to have  simmered down now, but it's not known for sure whether or not a bigger  eruption is yet to follow. Even though eruptions of Popo have been a fact  of life for centuries, there has been no recorded catastrophic loss of  life, but that doesn't mean it can't or won't happen. Popo erupts  periodically, and since Herman Cortez vanquished Mexico almost 500 years  ago, there have been at least 15 episodes of heighten activity. Supposedly,  Cortez sent some of his troops into Popo's crater to retrieve sulfur for  making gunpowder. You can see why the Aztecs feared the Spaniards. From  their point of view, they wore fierce looking armor, sailed strange looking  vessels, and climbed into volcanoes and came back with sticks that fired  pieces of lead. The fact that they exposed the Aztecs to terrible diseases,  such as smallpox, made their fears justified.

Popo is a stratovolcano in the central volcanic belt of Mexico. These  explosive-type volcanoes are especially dangerous. They're recognized by  their generally steep-sided, symmetrical cones that have built up by the  accumulation of debris from previous eruptions. They consist of alternating  layers of lava flows, volcanic ash and cinder. Mount Usu and Mount Fuji in  Japan, Mount Shasta in California, Mount Hood in Oregon, and Mount St.  Helens and Mount Rainier in Washington are all examples of stratovolcanoes.  Ash and pyroclastic flows (high speed, superheated flows of ash, rocks,  mud, and gas) are responsible for most of the deaths from these volcanoes.  In 1902, 30,000 people were killed by pyroclastic flows when Mt. Pelee  erupted on the island of Martinique! Pyroclastic flows would be an  immediate danger to people living with about 7 miles of Popo and could kill  everyone in their path. An additional concern with Popo at this time of  year is the probability that a major eruption would melt the deep deposits  of snow on its flanks, leading to a fast moving and deadly slurry of ice,  water and mud. The mudflows, or lahars, could be a problem for a number of  years after a major eruption, especially during the rainy season.

In contrast to stratovolcanoes, shield volcanoes, such as the ones on  Hawaii, erupt non explosively. Their lavas can flow considerable distances  from the active vents, and while these gently sloping volcanoes can destroy  property when they erupt, fatalities occur infrequently.

Many people living near Popo seemed surprised by its recent eruption. They  just didn't expect a major eruption to occur during their life-times. The  real surprising thing is how often people say they're surprised when a  natural disaster like this happens. If you live near a fault, how can you  be shocked when there's an earthquake, and likewise, if you live near a  17,000 foot peak with a name that is Aztec for "smoking mountain," how can  you be surprised when it erupts? I guess human nature is such that we try  to block out the possibility of bad things happening to us.

In any given week or month, a number of volcanoes are likely to be either  actively erupting or undergoing high levels of seismicity. For the most  part, they seldom make the nightly news. For instance, for the last week of  December and the first week of January, eruptions occurred in Ecuador, the  Kamchatka Peninsula of Russia, Kilauea on Hawaii, Montserrat in the West  Indes, as well as Popo. Because several of these volcanoes are in pretty  remote parts of the world, when they erupt, there not apt to be witnessed  by many people. In 2000, there were nearly 40 eruptions that occurred in  various geographic locations around the world. Some were shield volcanoes,  and some were stratovolcanoes. Most erupted in sparsely populated places  such as southern Chile, the Solomon Islands, Unimak Island in Alaska, Papua  New Guinea, and the Congo.

One other thing that makes Popo so perilous is its proximity to nearby  villages, towns and even large cities. If the land surrounding the volcano  is fertile, as it often is, and if the climate or geography is favorable  for settlement, then people will live there even if the risks are high. In  the eruption of 822 A.D., the lower portion of the great pyramid of Cholula  was buried by a lahar, and archaeological evidence indicates that the  Cholula area was abandoned about this same time. With the possible  exception of Mt. Fuji, more people live closer to Popo than any other  volcano in the world. Upwards of 30 million people live within view of  Popo, and tens of thousands live close enough to be in harms way if Popo  explodes catastrophically. While over 50,000 thousand people were evacuated  in December, many people are refusing to budge. They may pay the price for  being too cavalier toward this smoking giant.

For more about this see the science question for April 20, 2000 and look at  the following web sites:
http://volcano.und.edu/vwdocs/current_volcs/current.html 
http://epod.usra.edu/archive/epodviewer.php3?oid=44288