Navigation
Contribute
Sister projects
From WinkyPedia, the free encyclopedia that tells you what you already knew
A volcano is a mountain with a hole in the top through which the inside of the Earth occasionally becomes the outside of the Earth. Geologists consider this the planet's way of showing its working.[1]
Unlike most mountains, which were pushed up from below, a volcano builds itself one layer at a time, entirely from rock it has melted down and poured over itself. It is, in this sense, the only mountain that is self-made, and it does not let the others forget it.
Volcanoes are officially classed as active, dormant or extinct. A volcano is active if it is erupting, dormant if it is not erupting, and extinct if it is not erupting with more conviction.[2]
The difference between dormant and extinct is decided by the International Panel on Volcanic Sleep, which meets at the foot of each volcano every thousand years and watches it carefully for a day. If nothing happens, the volcano is reclassified as extinct and the panel leaves quickly, just in case.
Lava is rock that has been heated until it is no longer prepared to be a rock. It flows downhill, because it is still, at heart, quite heavy. Once it cools it becomes rock again and never mentions the whole episode.
Lava is hot. Measurements taken over two centuries have repeatedly confirmed this, at a slightly increasing distance each time.
When a volcano erupts it can send a cloud of ash several kilometres into the sky. The ash eventually comes back down, which is the main thing everyone underneath it would like to know about ash.