Volcanoes erupt every week around the world (just check out the weekly reports from Smithsonian's Global Volcanism Program and you'll see what I mean), but most of them don't cause problems. Those that do, including the Icelandic volcano Eyjafjallajökull that shut down European airspace for days, are really nothing more than an inconvenience on a historical scale. They don't kill people (Eyjafjallajökull displaced about 800 Icelanders but has had no deaths associated with it so far) and quietly erupt in a way that makes us often forget they're even there. Sure, they'll occasionally send out a plume that will disrupt air traffic—the Alaska Volcano Observatory, for instance, sends out warnings whenever volcanoes in its vicinity start acting up and spewing ash that airplanes should avoid—or ooze lava that will destroy a handful of homes, but the really destructive eruptions are, thankfully, few and far between. Here are the six worst since 1700:
Lakagígar (Laki), Iceland, 1783: This volcano spewed 100 million tons of sulfur dioxide and other toxic gases, killing 20 to 25 percent of Iceland's 50,000 people and thousands more in England and Europe, along with livestock and vegetation. Models of the eruption suggest it may have been responsible for a weak Asian monsoon season and a famine in Egypt.
Unzen, Japan, 1792: In Japan's worst volcanic disaster, a month after the volcano stopped spewing lava, the collapse of a lava dome triggered a landslide and tsunami that killed more than 15,000 people.
Tambora, Indonesia, 1815: The most explosive eruption in recorded history, Tambora killed thousands on Sumbawa Island and triggered a tsunami that killed around 4,600. Tens of thousands more died of starvation and disease in the following months. Global temperatures dropped by 7 degrees Fahrenheit and 1816 became the "year without a summer" in Europe and North America, which may have inspired Mary Shelley's Frankenstein.
Krakatau, Indonesia, 1883: A series of four explosions—so violent they could be heard 2,200 miles away in Perth, Australia—caused the collapse of the volcano and triggered a tsunami that was responsible for at least 36,000 deaths (though some estimate that more than 120,000 may have died). Global temperatures fell in the following year, and weather patterns did not return to normal until 1885 (though the red sunsets may have inspired Edvard Munch's Scream).
Mont Pelée, Martinique, 1902: Hot gas and rock moving as fast as 100 miles per hour or more descended on the town of St. Pierre, killing 30,000 in minutes.
Nevado del Ruiz, Columbia, 1985: When this volcano exploded, the hot gas and ash rapidly melted the glacier that had covered the summit. The resulting lahars—volcanic mudflows—were as much as 130 feet thick and traveled as fast as 30 miles per hour. The town of Armero, 45 miles away, was swept away by a lahar two and a half hours after the eruption began, killing 23,000.
If you've been inconvenienced by the Icelandic volcano's ash plume and had to cancel a trip or been stuck far from home, I do feel sorry. However, just think, it could have been a lot worse.