Tweed Volcano was an Early Miocene shield volcano in northeastern New South Wales, Australia. In the course of about three million years, Tweed Volcano was formed over the East Australia hotspot when this part of the continent passed over it around 23 million years ago. Mount Warning, Lamington Plateau and the Border Ranges between New South Wales and Queensland are among the remnants of this volcano that was originally over 100 km in diameter and nearly twice the height of Mount Warning today (1,156 m). Despite its size, Tweed Volcano was not a supervolcano; other shield volcanoes - such as on Hawaii - are much larger. In the 23 million years since the volcano was active, erosion has been extensive, forming a large erosion caldera around the volcanic plug of Mount Warning. Its erosion caldera is the largest in the Southern Hemisphere.^[2]

• http://en.wikipedia.org/wiki/Tweed Volcano