The Anahim volcanoes are grouped into three types: volcanic cones, shield volcanoes and lava domes. The shields are characterized by their large size (hundreds of kilometres in volume) and their symmetrical shape. They are the most prominent of the three volcano types, with the Rainbow Range being the highest at around above sea level. Their outer slopes merge with older flat-lying basalt flows of the Chilcotin Group, which covers a large percentage of the Interior Plateau. The more abundant lava domes and volcanic cones are much smaller in size (less than one kilometre in volume). These comprise two extensive volcanic fields in the vicinity of the Itcha Range.