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The summit craters represent the junction area of the volcanic activity through which breathes the persistent vent of Etna, and in more or less regular intervals, are the site of explosive events of various types as: Strombolian obstruction phreatic activities etc. that continually change the morphology.
Stratovolcanoes sometimes have a crater at the summit that is formed by explosive ejection of material from a central vent. Sometimes the craters have been filled in by lava flows or lava domes, sometimes they are filled with glacial ice, and less commonly they are filled with water.