Tweed Volcano

Tweed Volcano
After activity ceased, the volcano rapidly eroded. Pictured here is Mount Warning, a volcanic plug that marks where the summit used to be.
Highest point
Elevation	~1,900-2,312 m (6,200-7,586 ft)
Geography
Location	Northeastern New South Wales
Parent range	Great Dividing Range
Geology
Age of rock	Over 23 Million Years
Mountain type	shield volcano
Last eruption	~23 Ma

Tweed Volcano is a partially eroded Early Miocene shield volcano located in northeastern New South Wales, which formed when this region of Australia passed over the East Australia hotspot 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 kilometres (62 mi) in diameter and nearly twice the height of Mount Warning today, at 1,156 metres (3,793 ft). 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.

Lavas from the Tweed Volcano are recognised as part of the Lamington Volcanics.

The volcanic stratigraphy of the Tweed Volcano is similar to many other hotspot volcanoes around the world. Eruptions of tholeiitic and some calc-alkaline basalts are the oldest recognised units derived from the volcano. These are named the Lismore Basalt and Beechmont Basalt in New South Wales and Queensland respectively. There are numerous flows recorded which may have been erupted irregularly as fossil soil (Paleosol) profiles and lacustrine type rock units are occasionally found within the rock unit.