Darn volcanoes have no respect for national boundaries! Chaiten is soaking Argentina in ash, and they've had to shut down the main airport. This image is neat if looked at in detail.
There's good chance that it will go through a full cycle, like it did 7000 years ago. That means a collapse of the caldera, and a big explosion of hot gas and lava. Currently the sulfur production is real low, so we don't have to worry about the tomatoes! And this would be confined to the S. Hemisphere anyway.