Volcanoes are one of nature's great wonders. For years they can stand dormant, but once active they can erupt in tremendous explosions of power. Some eruptions are so big, they change the earth's climate. Luckily, geologists can now approximate when an eruption will occur. What are the causes of an eruption and what are the warning signs? Read and find out!Lloyd, Megan is the author of 'Volcanoes ', published 2007 under ISBN 9780064451895 and ISBN 0064451895.