The Mount Napier Lava Flow followed the Harman Valley west from the volcano, and then south towards nearby Mount Eccles which is 25 km south-west of Mount Napier. Lava blisters or tumuli occur along the flow - these are house-sized mounds of basalt rocks. The blisters are the best developed in Australia and uncommon in the rest of the world. They are formed by the pressure of liquid lava pushing up against the crust. Several caves and lava tubes can also be found at Byaduk.