Like many of Tasmania's mountains, Mount Wellington consists of volcanic dolerite, i.e. lava pressed through vents in now eroded layers of sedimental rock. Slowly cooling off, the lava formed hard cores and sometimes roughly hexagonal columns, densely packed, which under erosion break up and form hedgehog-like landscapes like above. The geology is similar to Chile, being "only" 11'000 km away, which even in 1953 made an experienced geologist, Charles F. Laseron, author of "The Face of Australia", speculate about a land bridge drowned under the Pacific. Never heard about continental drift, it seems...