Shield volcanoes usually erupt with splattering liquid lava that fountains out and has little explosive potential. This forms some of the largest volcanoes on Earth with very gentle slopes, since the liquid water cannot build steeper slopes. This type of lava cools to form basalt rock.
Shield volcanoes erupt the way they do because of a steady supply of hot magma that is altered little from when it formed. They frequently occur over volcanic hotspots, but they may also occur in chains over subduction zones or all by themselves. Examples of shield volcanoes are found in the Hawaiian and Galapagos islands. Shield volcanoes go through active and inactive periods. During active periods, their peaks are full of lava that sputters out around the opening. During inactive periods, the lava cools and collapses, creating a hollow known as a caldera.
Shield volcanoes are only one of several types of volcanoes. Lava domes are formed by viscous lava that comes to the surface. They can be quite explosive, but the lava does not flow far following an eruption. Cinder cones often only erupt once, and these may form a volcano between 300 and 400 feet in height composed of rock materials resembling cinders.