Mount Napier or Tapoc in the local Aboriginal language, has a composite lava shield with a superimposed scoria cone. The cone rises above the surrounding plains to an elevation of , making it the highest point on the Western District Plains of Victoria. Mount Napier is part of the Newer Volcanics Province, which is the youngest volcanic region in Australia. The Newer Volcanics Province covers an area of and contains over 400 vents.