All volcanoes have the same basic parts. The summit crater is the mouth of the volcano where the lava comes out. The magma chamber is where the magma wells up underground. The central vent connects the magma chamber to the summit crater. Around the central vent is the volcano's edifice. The different shapes of volcanoes are characterized by the shapes of their summits and edifices.
• Stratovolcanoes have steep, symmetrical sides leading up to a small summit crater at the top.
• Scoria cone volcanoes have the most common volcano shape; this type also has steep, symmetrical sides, but with a very wide summit crater.
• Shield volcanoes are wide, short and get a bit steeper closer to their wide summit craters.
Volcanic activity creates other types of natural structures as well. One is the caldera, a large, crater-shaped basin that occurs when a magma chamber is completely drained of its magma. Once all the magma is gone, the volcano's edifice collapses into itself and water often fills it up. As a result, calderas can become lakes, such as Crater Lake in Oregon. Another type of volcanic structure is the lava dome. If the initial eruption causes most of the gas bubbles to escape, there isn't enough gas pressure to push out the rest of the lava. So the lava slowly pours out of the summit crater, which creates a dome shape as it plugs up the top of the volcano.
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