The Kerguelen Plateau (//, //) is an underwater volcanic large igneous province (LIP) and also a microcontinent and submerged continent in the southern Indian Ocean. It lies about 3,000 km to the southwest of Australia and is nearly three times the size of Japan. The plateau extends for more than 2,200 km in a northwest-southeast direction and lies in deep water.
The plateau was produced by the Kerguelen hotspot, starting with or following the breakup of Gondwana about 130 million years ago. There is a small portion of the plateau that breaks sea level, forming the Kerguelen Islands plus the Heard and McDonald Islands. Intermittent volcanism continues on the Heard and McDonald Islands.
Symmetrically located across the Indian Ocean ridge and due west of Australia is the Broken Ridge underwater volcanic plateau, which at one time was contiguous with the Kerguelen Plateau prior to rifting by the mid-ocean ridge.
The formation of the Kerguelen Plateau started with a series of large volcanic eruptions 110 million years ago. The presence of soil layers in the basalt with included charcoal and conglomerate fragments of gneiss indicate that much of the plateau was above sea level as what is termed a microcontinent for three periods between 100 million years ago and 20 million years ago. The so-called Kerguelen microcontinent may have been covered by dense conifer forest in the mid-Cretaceous. It finally sank 20 million years ago and is now 1 to 2 km (0.6 to 1.2 mi) below sea level.
- Oxford English Dictionary
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