Tasmantid Seamount Chain: A Volcanic Legacy in the South Pacific
Hidden beneath the surface of the South Pacific Ocean lies a massive geological feature known as the Tasmantid Seamount Chain. Stretching across the depths of the Coral and Tasman Seas, this chain of extinct volcanic peaks provides a window into the tectonic movements that have shaped the region east of Australia over millions of years.
The Nature of the Tasmantid Seamounts
The Tasmantid Seamount Chain (also referred to as the Tasman Seamounts or Tasmantide Volcanoes) is a linear sequence of underwater mountains. A seamount is an underwater mountain formed by volcanic activity that does not reach the ocean surface. This specific chain extends for approximately 2,000 km (1,200 mi), consisting of more than 16 extinct volcanic peaks.
Many of these peaks are immense, rising more than 4,000 m (13,000 ft) from the ocean floor. The chain runs north-south, positioned at approximately 156°E longitude, making it one of two parallel seamount chains located off the east coast of Australia, the other being the Lord Howe chain (located at approximately 159°E).
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Geological Origins and Formation
The formation of the Tasmantid Seamount Chain is a result of hotspot volcanism. This occurs when a tectonic plate moves over a stationary hotspot—a localized area of intense heat in the Earth's mantle that melts the overlying plate to create volcanoes.
In this case, the Indo-Australian Plate moved northward over a stationary hotspot, leaving a trail of volcanic peaks in its wake. Because the plate continued to move while the hotspot remained fixed, the volcanoes became extinct as they were carried away from their magma source. The age of the rocks within the chain ranges from approximately 56 million to 7 million years old.
Key Facts
- Total Length: Approximately 2,000 km (1,200 mi).
- Composition: Over 16 extinct volcanic peaks.
- Maximum Height: Some peaks rise over 4,000 m (13,000 ft) from the seabed.
- Location: South Pacific Ocean, spanning the Coral Sea and Tasman Sea.
- Age Range: 56 to 7 million years.
- Tectonic Driver: Northward movement of the Indo-Australian Plate over a stationary hotspot.
Named Features of the Chain
The chain includes a variety of geological features, ranging from deep seamounts and guyots (flat-topped seamounts) to coral reefs that have formed on the shallower peaks.
| Feature Name | Type |
|---|---|
| Mellish Reef, Kenn Reef, Wreck Reefs, Cato Reef | Coral Reefs |
| Fraser, Moreton, Mooloolaba, Stradbroke, Kimbla, Gascoyne | Seamounts |
| Recorder, Brisbane, Queensland, Britannia, Hunter | Guyots |
| Taupo Bank, Barcoo Bank | Banks |
| Derwent | Seamount |
Frequently Asked Questions
What is the Tasmantid Seamount Chain?
It is a 2,000 km long chain of over 16 extinct volcanic peaks located in the South Pacific Ocean, specifically within the Coral and Tasman Seas east of Australia.
How were these seamounts formed?
They were formed by the Indo-Australian Plate moving northward over a stationary hotspot in the Earth's mantle, which created a sequence of volcanoes over time.
How old are the Tasmantid Seamounts?
The volcanic rocks in the chain date back between 56 million and 7 million years.
What is the difference between the Tasmantid and Lord Howe chains?
While both are parallel north-south chains off Australia's east coast, the Tasmantid chain is located at approximately 156°E, while the Lord Howe chain is located at approximately 159°E.
Do any of these seamounts reach the surface?
While many are deep underwater, some have become coral reefs, such as Mellish Reef and Wreck Reefs.