Why Have There Been So Many Geological Catastrophes Lately?

These days, you don’t have to be a conspiracy theorist or religious fanatic to wonder whether there’s something strange going on with the Earth. Major earthquakes in Haiti, Chile, and China have killed thousands, and a cloud of volcanic ash has grounded flights across Europe. This past weekend also saw deadly quakes in Afghanistan , Papua New Guinea , and the Dominican Republic . So is the Earth going through a period of especially high geological activity?

No, we’re just paying more attention. 2010 is actually shaping up to be a perfectly average year for quakes. According to the U.S. Geological Survey , since 1900 the Earth has experienced an average of 16 major quakes — magnitude 7.0 or higher — per year. In the first four months of 2010, there have been six. So though this will likely be a worse year than 1986, when there were only six major quakes total, it’s unlikely to be as bad as 1943, when there were 32. And while major earthquakes like the ones in Haiti and Chile typically cause numerous aftershocks, scientists don’t think that they are directly causing each other.

So why does it seem like this has been a particularly bad year? It likely has something to do with increased media coverage. This weekend’s quake off the coast of the Dominican Republic is thought to have killed only three people and probably wouldn’t have garnered much international attention if not for the catastrophic temblor that struck nearby Haiti in January.

But while earthquakes haven’t become more frequent, they are getting more deadly. Earthquakes killed 650,000 people in the last decade, more than any other decade in history. Around 250,000 have already died this year. This is likely because of the expansion of urban areas in fault zones. China’s Qinghai province has experienced 53 magnitude 5.0 or higher quakes since 2001, but it wasn’t until one struck near the population center in Yushu that the casualty numbers exploded.

As for volcanoes, while the Eyjafjallajokull eruption may be causing chaos on the continent, it’s not all that unusual for Iceland, which sits right on top of the Mid-Atlantic Ridge fault line and boasts 130 volcanoes of various levels of activity. This month’s eruption is mild compared with the 1783 Laki eruption which caused a famine that wiped out a quarter of Iceland’s population and altered climate patterns in Northern Europe for years. Obviously, there were no jets to worry about back then.

Eyjafjallajokull may be no Mount Pinatubo, whose powerful 1991 eruption had wide-ranging effects on the Earth’s climate, but its ash has been especially disruptive because the height of its plume, about 20,000 to 30,000 feet, is high enough to get caught in prevailing winds and spread over a large area.

It’s also been well known for some time that jets and volcanic ash are not a good combination. Since an eruption from Alaska’s Mount Redoubt nearly took down a KLM 747 in 1989, the U.S. Geological Survey has kept close tabs on the volcanoes of the Aleutian Islands, which run across a popular route for jets crossing the Pacific. The Federal Aviation Administration imposed a no-fly zone around Mt. Redoubt during an eruption as recently as last year. Of course, unlike with the Aleutians, airlines can’t exactly just go around continental Europe.

Thanks to geophysicist Don Blakeman of the U.S. Geological Survey and Frank Spera, professor of earth sciences at the University of California at Santa Barbara.