Mount Fuji. . Some of the Earth's biggest and most beautiful mountains are composite or stratovolcanoes. The cones of these volcanoes are tall and thin. When the magma is thick, the gas cannot escape, so it builds up until it explodes and sends out huge clouds of burning rock and gas. Most stratovolcanoes have a crater at the summit which contains a central vent or a group of vents. An example is Mount Fuji in Japan. . Shield volcanoes are built up slowly by thousands of very fluid lava flows. 0 Flow after flow runs out in all directions from a vent in the summit, or group of vents. These flows build a large, gently sloping 0 cone that looks like a shield. Some of the largest volcanoes in the world are shield volcanoes. Mount Etna in Sicily is an example of a shield volcano.