The Broken Ridge or Broken Plateau is an

oceanic plateau An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides. There are 184 oceanic plateaus in the world, covering an area of or about 5.11% of the o ...

in the south-eastern

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

. The Broken Ridge once formed a

large igneous province A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive ( sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The format ...

(LIP) together with the Kerguelen Plateau. When Australia and Antarctica started to separate, the Broken Ridge and the Kerguelen Plateau got separated by the Southeast Indian Ridge. Alkalic

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

from the Broken Ridge has been dated to 95 Ma. The Broken Ridge stretches from the southern end of the Ninety East Ridge towards the south-western corner of Australia. It is up to wide and reaches below sea level. It is separated from the Diamantina fracture zone on its southern side by a escarpment, while on the northern side the ridge slopes gently towards the abyssal Wharton Basin. The sediment cover on the ridge reaches and the Moho is found at about . It is separated from the Naturaliste Plateau by the Dirck Hartog Ridge. The Kerguelen LIP covered making it the second largest LIP on Earth (after the Ontong Java Plateau in the Pacific). Both these enormous LIPs reaches above the surrounding ocean floor and have a crustal thickness of (compared to oceanic crust typically around thick.) The Broken Ridge and Kerguelen Plateau are now separated by . When they broke up, the southern flank of Broken Ridge was uplifted some and reached above sea level. The Kerguelen LIP has a long and complicated history, however, and is probably the least "typical" of all LIPs. Rocks from both the Broken Ridge and the Kerguelen Plateau contain a continental component or "fingerprint". In the Early Cretaceous, the Kerguelen hotspot was split into several diapirs of various sizes, composition, and ascent rates. These separate diapirs created the Bunbury Basalt, the Southern Kerguelen Plateau, the Rajmahal Traps/Indian

lamprophyre Lamprophyres () are uncommon, small-volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks, and small intrusions. They are alkaline silica- undersaturated mafic or ultramafic rocks with high magnesium o ...

s, Antarctic lamprophyres, and the Central Kerguelen Plateau/Broken Ridge. In the late Cretaceous, activity in the mantle slowed and the Kerguelen hotspot was reduced to a single plume which created the Ninety East Ridge. 120–95 Ma when the Southern and Central Kerguelen Plateau formed together with the Broken Ridge, the Kerguelen hotspot produced /year, but 95–25 Ma the output decreased to .

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* * * * {{Large igneous provinces Large igneous provinces Plateaus of the Indian Ocean Cretaceous volcanism