Oceania lies between Asia and South America and the Antarctica. Australia the biggest land mass is actually greater in size than all the other islands of Oceania combined. New Guinea is the second biggest island followed by New Zealand. New Zealand is bigger than all remaining islands. The next biggest island is New Caledonia which is joined to to New Zealand via a mainly submerged landmass called Zealandia. During glacial periods more of Zealandia becomes terrestrial rather than a marine environment.