Kerguelen Plateau

Lore & Background

The Kerguelen hotspot has produced basaltic lava for about 130 million years. The oldest volcanic rocks assigned to it are from the Early Cretaceous in the Comei large igneous province of southeastern Tibet, dated from 145 million years ago. The Southern Kerguelen Plateau formed between 120 to 110 million years ago, consistent with a large igneous province. The Central Kerguelen Plateau formed between 110 to 100 million years ago. The Northern Kerguelen Plateau was created by the hotspot after the opening of the Southeast Indian Ridge at 40 million years ago. The most recent activity has been near Heard Island and McDonald Islands, where there are two active volcanoes. The current location of the hotspot could be a wide area of the Central Kerguelen Plateau extending over about 440 km, back into the Kerguelen Archipelago, where there is current geothermal activity with active fumaroles.

Reader's Guide

The Kerguelen hotspot has produced several widely dispersed features. These include the Kerguelen Islands, Naturaliste Plateau, Heard Island, the McDonald Islands, the Comei large igneous province in south Tibet, and the Rajmahal Traps. One associated feature, the Ninety East Ridge, is distinguished by its over 5,000 km length, being the longest linear tectonic feature on Earth. The bulk of the Kerguelen Islands alkalic flood basalts were deposited between 30 and 24 million years ago. Younger lavas towards the southeast of the archipelago, found as dykes or plugs, have ages between 10 and 6 million years. To the south, the stratovolcano of Mont Ross on Grande Terre is between 2 million years and 100,000 years old. The Amsterdam–St. Paul Plateau, located near the current plate boundary of the Southeast Indian Ridge, has compositional similarities to the Kerguelen hotspot's eruptives, leading some to assign its recently active volcanoes to this hotspot rather than a separate Amsterdam-Saint Paul hotspot.

Did You Know?

• The Ninety East Ridge, associated with the Kerguelen hotspot, is over 5,000 km long, making it the longest linear tectonic feature on Earth.
• The total volume of magma erupted by the Kerguelen hotspot over 130 million years has been estimated at about 25,000,000 km³.
• The most recent volcanic activity of the Kerguelen hotspot has been near Heard Island and McDonald Islands, which have two active volcanoes.
• The Comei large igneous province in south Tibet contains the oldest volcanic rocks assigned to the Kerguelen hotspot, dating from 145 million years ago.
• The bulk of the Kerguelen Islands' alkalic flood basalts were deposited between 30 and 24 million years ago.

A 130-Million-Year Volcanic Engine

The Kerguelen hotspot has been producing basaltic lava for roughly 130 million years, making it one of the longest-lived volcanic sources on Earth. Over that vast span, it generated not just the Kerguelen Plateau itself but a remarkable constellation of geological features: the Kerguelen Islands, the Naturaliste Plateau, Heard Island, the McDonald Islands, the Comei large igneous province in south Tibet, and the Rajmahal Traps. The cumulative volume of magma erupted, including all associated features, is estimated at approximately 25 million cubic kilometers (about 6 million cubic miles). However, this figure carries uncertainty because the hotspot did not operate in isolation; it interacted with seafloor spreading systems, meaning some of the erupted material is difficult to attribute cleanly to the plume alone. The sheer longevity and geographic spread of this volcanic output—stretching from the Southern Indian Ocean to the Tibetan plateau—make the Kerguelen system one of the most extensive volcanic records preserved in Earth's crust.

The Ninety East Ridge and Plate Divergence

One of the most striking features linked to the Kerguelen hotspot is the Ninety East Ridge, a submarine ridge stretching over 5,000 kilometers (approximately 3,100 miles), making it the longest linear tectonic feature on the planet. The ridge is not merely a passive geological scar; it also functions as part of the diffuse boundary between the Indian Plate and the Australian Plate as those two fragments drift apart toward the north. Recent research, supported by seismic evidence including the 2012 Indian Ocean earthquakes, suggests the Indo-Australian Plate may have fractured into two or even three separate plates, with the Indian and Australian Plates potentially having been distinct since at least 3 million years ago. The ridge thus sits at the intersection of hotspot volcanism and active plate divergence. Additionally, present-day structures in the region, such as the Elan Bank, may owe their positions to ridge jumps that occurred during propagating rifts in the seafloor spreading process.

Still Bubbling: Recent and Historic Volcanism

The Kerguelen hotspot is far from a geological relic. Its most recent volcanic activity has been concentrated near Heard Island and the McDonald Islands, where two volcanoes remain active. Yet the hotspot's present-day location is debated; some plate tectonic models place it across a broad zone of the Central Kerguelen Plateau spanning roughly 440 kilometers, while others point back toward the Kerguelen Archipelago, where active fumaroles evidence ongoing geothermal activity. On Grande Terre, the stratovolcano Mont Ross dates between 2 and 0.1 million years old, and younger lavas in the archipelago's southeast, preserved as dykes and plugs, range from 10 to 6 million years. Further afield, the Boomerang Seamount erupted in 1995, and Île Saint-Paul last erupted in 1793. Some researchers even assign the recently active volcanoes of the Amsterdam–St. Paul Plateau to the Kerguelen system rather than a separate hotspot, though this remains contested.

Writing Gondwana's Breakup in Basalt

The volcanic record of the Kerguelen hotspot serves as a chronological archive of the breakup of the supercontinent Gondwana. The oldest rocks attributed to this system erupted during the Early Cretaceous, around 145 million years ago, forming the Comei large igneous province in southeastern Tibet. These basalts overlap in age with those found at Bunbury, Western Australia, which range from 137 to 123 million years old. Around 132 to 130 million years ago, India began separating from Antarctica, and between 132.6 and 96 million years ago, East Gondwana—comprising Antarctica, India, and Australia—underwent progressive fragmentation. India initiated its collision with Asia roughly 70 million years ago, while Eastern Australia and Antarctica completed their separation perhaps as recently as 45 million years ago. The hotspot's trail of volcanic deposits thus traces the successive rifts that tore a supercontinent apart, with each age-dated lava flow marking a chapter in one of Earth's most dramatic tectonic reorganizations.