The Kerguelen Plateau is located in the Indian Ocean, and is the longest continually erupting supervolcano. From 90 to 120 million years ago, basaltic lava eruptions from fissures on the seabed led to the formation of a volcanic plateau that eventually rose above the sea level. The presence of soil layers and charcoal from previous vegetation in the basalt indicates that the Kerguelen Plateau was once above sea level. Due to the volcanic rock sinking slowly, the Kerguelen Plateau is currently oceanic, 1000-2000m below the sea level. The Kerguelen Islands, (French territory) and the Heard and McDonald Islands (Australian territory), are the only parts of the plateau that remain above the sea level (Bressan, 2020).
The Kerguelen Plateau is classified as a Large Igneous Province (LIP). LIPs are formed as a result of massive volcanic events. They are formed due to the accumulation of basalt and volcanic rocks. LIPs can form on existing continents, in the ocean or at tectonic plate boundaries (Coffin, 1994). The Kerguelen Plateau has an area of 1250000 sq km. To put things in perspective, its area can be compared to half the size of the Australian continent.
The plateau is situated in the temperate zone of the Southern Hemisphere. It is a part of the sub-Antarctic shelf (Barnes et al., 2018). On the map, it can be found between Africa and Australia, towards the south of both continents.
Why is there volcanic activity even today?
The unique geological features of Kerguelen Plateau make it conducive for volcanic activity. The edges of three large tectonic plates are found in the Indian ocean – the African, the Antarctic and the Australian plates. The Kerguelen Plateau was initially located in between the Antarctic and Australian plates, which was a hot-spot of volcanic activity. This provided the heat needed to melt the rocks and the magma spread along the ridge between the tectonic plates. The magma cooled and solidified to form the plateau.
The Kerguelen Plateau drifted towards the south across millions of years, moving away from the volcanic hotspot. Thus, though it is still volcanically active due to its location, the frequency of these eruptions has decreased (Bressan, 2020).
The ecosystem comprising the plateau, Kerguelen islands and the Heard and McDonald Islands are isolated from the mainstream human settlements. The plateau is home to rich biodiversity. It supports the growth of these species as the mineral content from the volcanic eruptions make the region nutritious.
The plateau is home to a rare and expensive variety of fish called the Patagonian toothfish. It is also called the Chilean seabass, sold in the market at high prices. The white flesh of these fish is considered as a delicacy and is said to be healthy. The toothfish populations are vulnerable to unsustainable fishing and illegal poaching (Dell, 2019).
Since the toothfish is a top predator, it has ecological importance in balancing the population of other marine species it feeds on, maintaining the food chain and structure of the ecological community.
The banks of the plateau are inhabited by coral species, crustaceans, sponges and anemones. They are slow growing communities, and ecologically sensitive to anthropogenic disturbances.
The plateau intercepts the strong water currents around the south pole. There is an upwelling of cold water from the depths of the sea with volcanic minerals to the surface, which again returns to the bottom. This nutrient transport supports diverse marine life and a food cycle from zooplankton to penguins, albatross, elephant seals and sperm whales. The seabed supports invertebrates and fish species that are only present due to the nutrients from the plateau (Dell, 2019).
Implication for climate change
Ocean currents from the tropical deep-sea carry nutrients towards the Arctic and Antarctic regions. There are no primary producers at the poles because phytoplankton (consumed by small organisms which are then consumed by the predators) do not survive in the frigid temperatures. So, the nutrients are transported back to the tropical regions by the currents.
In the case of global warming, the poles receive more sunlight because of the melting glaciers. The warming conditions allow for phytoplankton to grow. Therefore, the polar regions and the surrounding oceanic environment will utilize more nutrients and support marine species that migrate to cooler, polar waters.
The location of the Kerguelen Plateau close to the south pole makes it important for scientists to understand the pole-ward shift of marine organisms due to climate change (Dell, 2019). The plateau is being studied to understand how this change will impact oceanic ecosystems near the equator and vulnerable species.
Blue carbon sequestration
Blue carbon sequestration refers to the carbon removed from the atmosphere and stored in coastal and marine ecosystems.
Snowmelt in the polar region results in increased phytoplankton bloom due to the sudden increase in sunlight and heat. This increases the carbon sequestration abilities of the region, which is negative feedback on climate change (i.e., slows the rate of global warming by capturing atmospheric carbon near the poles) (Barnes et al. 2018).
Research shows that the Kerguelen Plateau has potential for blue carbon sequestration in the future while supporting marine biodiversity. There was an increase in organisms at the Kerguelen region across the past decade, suggesting that carbon storage would have also increased (Bax et al., n.d).
Oceans are carbon sinks – dead marine organisms are decomposed and the carbon is sequestered at the seabed. Phytoplankton at the surface of the water uptake carbon for their growth.
The Kerguelen Plateau’s features and location could help provide a better understanding of marine ecology and the changes caused by climate change. There is still a lot of research left to do, and is being undertaken by various international organizations.
The Kerguelen Plateau and its islands are a fragile ecosystem. Since it is isolated from human activity, it is also important from the aspect of biodiversity conservation.
Barnes, D., Fleming, A., Sands, C., Quartino, M., & Deregibus, D. (2018). Icebergs, sea ice, blue carbon and Antarctic climate feedbacks. Philosophical Transactions Of The Royal Society A: Mathematical, Physical And Engineering Sciences, 376(2122), 20170176. https://doi.org/10.1098/rsta.2017.0176
Bax, N et al. Carbon storage by Kerguelen zoobenthos as a negative feedback on climate change. The Kerguelen Plateau: Marine Ecosystem + Fisheries Proceedings of the Second Symposium. Retrieved 13 June 2022, from http://heardisland.antarctica.gov.au/__data/assets/pdf_file/0019/229141/18-Bax-EA.pdf.
Bressan, D. (2020). Kerguelen Plateau Is Earth’s Longest Continuously Erupting Supervolcano. Forbes. Retrieved 13 June 2022, from https://www.forbes.com/sites/davidbressan/2020/11/06/kerguelen-plateau-is-earths-longest-continuously-erupting-supervolcano/?sh=118a0ba032c8.
Coffin, M. (1994). Large Igneous Provinces. Retrieved 13 June 2022, from https://www.ldeo.columbia.edu/~polsen/nbcp/lipmc.html.
Dell, J. (2019). Australia’s only active volcanoes and a very expensive fish: the secrets of the Kerguelen Plateau. The Conversation. Retrieved 13 June 2022, from https://theconversation.com/australias-only-active-volcanoes-and-a-very-expensive-fish-the-secrets-of-the-kerguelen-plateau-123351.