Scientists say history has proven that when the Eyjafjallajokull volcano erupts, Katla follows – the only question is how soon. And Katla, located under the massive Myrdalsjokull icecap, threatens disastrous flooding and explosive blasts when it blows. Saturday’s eruption at Eyjafjallajokull – dormant for nearly 200 years – forced at least 500 people to evacuate. Most have returned to their homes, but authorities were waiting for scientific assessments to determine whether they were safe to stay. Residents of 14 farms nearest to the eruption site were told to stay away. Several small tremors were felt early on Monday, followed by spurts of lava and steam rocketing into the air. Iceland sits on a large volcanic hot spot in the Atlantic’s mid-oceanic ridge. Eruptions, common throughout Iceland’s history, are often triggered by seismic activity when the Earth’s plates move and when magma from deep underground pushes its way to the surface. Like earthquakes, predicting the timing of volcanic eruptions is an imprecise science. An eruption at the Katla volcano could be disastrous, however – both for Iceland and other nations. Iceland’s Laki volcano erupted in the mid-1780s, freeing gases that turned into smog. The smog floated across the Jet Stream, lowering temperatures and changing weather patterns. Many died from gas poisoning in the British Isles. Crop production fell in western Europe. Famine spread. Some even linked the eruption, which helped fuel famine, to the French …