Some steep sided ash and cinder cones are made of small fragments of magma exploded out of the vent (opening) On the other hand, quiet volcanoes emit streams of molten lava. If the lava is thick and pasty, it flows only a short distance before cooling. this lava creates steep sided mountains. Runny lava spreads out over large areas before cooling. Layer upon layer of this lava piles up in broad domes, or shield volcanoes, such as Mauna Loa in Hawaii. Most volcanoes are composite cones, consisting of alternating layers of ash and hardened lave.