Researchers have long known that modern humans lack the genetic variation found in other living primates, such as chimpanzees or gorillas, even though our current population size is so much larger. One explanation for this lack of variation is that our species underwent recent bottlenecks--events where a significant percentage were killed or otherwise prevented from reproducing. Some researchers proposed that the lack of variation in our maternally inherited mitochondrial DNA suggested these bottlenecks took place as our ancestors spread out of Africa relatively recently. One possibility occurred 70,000 years ago, when the Toba super-volcano erupted in Indonesia and triggered a nuclear winter that fewer than 15,000 individuals survived.

Polish authorities said Friday they may delay the weekend funeral of president Lech Kaczynski as a volcanic ash cloud threatened to disrupt the travel arrangements of dozens of world leaders. The country closed most of its airspace, calling into question the attendence of US President Barack Obama and other heads of state at late Polish leader's burial in the southern city of Krakow on Sunday.

It’s a much larger volcano, and in the past, we know its eruptions have been much larger, too,” Miller explains

...

And, Katla seems to erupt whenever Eyjafjallajokull does. Three times in history when Eyjafjallajokull has erupted—in 920, 1612 and 1821—Katla has, too.

That’s why the current eruption could be a bad omen: Every time Eyjafjallajokull has erupted—as it has for the past week—Katla follows behind, always erupting within the same year, sometimes just a few months after its little sister.

The blind side

For all the technology in the world, there's a huge blind spot in scientific understanding of Mount St. Helens - scientists still don't know how eruptions start in the first place.
"We have decent models of what we think the volcano looks like down to 6 miles (10 km) below the surface," Moran said. "From 6 to 20 miles down we don't have a very good idea. Geophysical imaging techniques haven't been very good at producing images at those depths."


The blind spot has led to even more puzzlement during a series of recent eruptions from 2004-2008, where the volcano only coughed up strangely solid magma that looked as though it had sat around for more than a decade - a stark contrast to the typically fluid magma (called lava once it breaks through Earth's surface).