What are some good and bad effects of Volcanic Eruptions?

Well, obviously volcanoes can kill a lot of people. ( I guess you knew that) The huge volcanic eruptions like Krakatoa in Sumatra and Pinatubo in the Philippines released huge amounts of ash and dust into the air which spread around the world. The temperatures dropped all around the world for a couple years after those eruptions. The lava flowing out of the volcanoes like in Hawaii and Iceland can destroy entire cities. However these lava flows also create new land at the edge of these islands. Volcanic ash is also very good for soil.