Shield volcanoes have gentle slopes and large diameters. They are formed by the accumulation of low viscosity basalt lava flows. Because the flows have low viscousity they flow a long way. Lava tubes form which enable molten lava to flow long distances from the vent. They form where large volumes of basalt lava are erupted over along period of time from one location such as over a hot spot/mantle plume.
They are called shield volcanoes ecause they look like a warriors shield.
The most famous and largest shield volcanoes in the world are those in Hawaii. Mauna Loa is the largest volcano on earth , Mauna Kea is 16000m tall from base to summit thats greate than Everest.Kilauea is still active and pours lava into the sea everyday.Al located on Big Island/Hawaii.