A shield volcano has broad, gentle slopes and is built by the eruption of fluid basalt lava. Basalt lava tends to build enormous, low-angle cones because it flows across the ground easily and can form lava tubes that enable lava to flow tens of kilometers from an erupting vent with very little cooling. The largest volcanoes on Earth are shield volcanoes. The name comes from a perceived resemblance to the shape of a warrior's shield.
Mauna Loa from Mauna Kea, Hawaii (1989). Photo: J. AleanShield volcano gallery