There are many types of igneous rocks. Volcanoes can damage themselves in the explosion. A volcano literally blows its top off. One of the volcanoes that has blown its top from an explosion is Mt. St. Helens. Mt. St. Helens has erupted more than once.
Volcanoes can be under water or on land.
It just depends on the environment how fast the volcano can make the magma the magma makes lava and the volcano makes an explosion. If the volcano is under water the cooled lava will probably make an island. The Hawaiian Islands is an example of island made by a chain of volcanoes. Now go back to the front page of our site and go to a different page on our site and of course be prepared to learn more about volcanoes.