Tweed Volcano was an early Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 shield volcano

Shield volcano

A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...

 in northeastern New South Wales

New South Wales

New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. In the course of about three million years, Tweed Volcano was formed over the East Australia hotspot

East Australia hotspot

The East Australia hotspot is a volcanic hotspot that forces magma up at weak spots in the Indo-Australian Plate to form volcanoes in Eastern Australia. There have been no eruptions in Australia during historic times. It does not produce a single chain of volcanoes like the Hawaiian Islands...

 when this part of the continent

Continent

A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...

 passed over it around 23 million years ago. Mount Warning

Mount Warning

Mount Warning is a mountain west-south-west of Murwillumbah, near the border with Queensland in the Northern Rivers region of New South Wales, Australia...

, 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

Kilometre

The kilometre is a unit of length in the metric system, equal to one thousand metres and is therefore exactly equal to the distance travelled by light in free space in of a second...

 in diameter

Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...

 and nearly twice the height of Mount Warning today (1,156 m). Despite its size, Tweed Volcano was not a supervolcano

Supervolcano

A supervolcano is a volcano capable of producing a volcanic eruption with an ejecta volume greater than 1,000 cubic kilometers . This is thousands of times larger than most historic volcanic eruptions. Supervolcanoes can occur when magma in the Earth rises into the crust from a hotspot but is...

; 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

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 caldera

Caldera

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

 around the volcanic plug

Volcanic plug

A volcanic plug, also called a volcanic neck or lava neck, is a volcanic landform created when magma hardens within a vent on an active volcano. When forming, a plug can cause an extreme build-up of pressure if volatile-charged magma is trapped beneath it, and this can sometimes lead to an...

 of Mount Warning. Its erosion caldera

Caldera

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

 is the largest in the Southern Hemisphere

Southern Hemisphere

The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

.

Volcanic Stratigraphy

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

The volcanic stratigraphy

Stratigraphy

Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....

 of the Tweed Volcano is similar to many other hot spot volcanoes around the world. Eruptions of tholeiitic and some alkaline basalts are the oldest recognised units derived from the volcano. These are named the Lismore/Beechmont Basalt in New South Wales

New South Wales

New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

 and Queensland

Queensland

Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...

 respectively. There are numerous flows recorded which may have been erupted erreguarly as soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 profiles and lacustrine

Lacustrine

Lacustrine means "of a lake" or "relating to a lake".Specifically, it may refer to:*Lacustrine plain*Lacustrine delta-Fish:*Lacustrine goby , a type of small fish found in Philippine waters belonging to the Gobiidae family, known in Tagalog as dulong-See also:*Fluvial - of or relating a...

 type rock units are occasionally found within the rock unit.

Following eruption of the Lismore/Beechmont Basalt a period of eruption of rhyolite

Rhyolite

This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...

 lavas took place. Eruptions occurred in lava

Lava

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

 and some pyroclasic

Pyroclastic rock

Pyroclastic rocks or pyroclastics are clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic...

forms. These rhyolites are known in New South Wales as the Nimbin Rhyolite and Queensland as the Binna Burra Rhyolite. Following eruption of this rhyolite a period of basaltic volcanism resumed (or continued) with the eruption of the Blue Knob(NSW)/Hobwee(QLD) Basalt.