A third type of volcano is the shield volcano. This type is built by fluid lava flows and has a gently sloping cone. Because the lava pours out in all directions, a shield volcano spreads in a wide area and builds up very slowly. Some shield volcanoes are three to four miles in diameter, but only rise 2,000 feet. The Hawaiian Islands are examples of shield volcanoes on a huge scale. Mauna Loa, one of the world’s most active shield volcanoes, is over 28,000 feet above the ocean floor. When the lava is so thick that it can’t move very far or very fast, lava domes are formed. The dome on this type of volcano grows from within. These sometimes form in the craters of large composite volcanoes.