Skip to main content

The origin of the Madagascar Ridge: three hypotheses

Expedition SO307 untersucht Geologie und Biologie des Madagaskar-Rückens. Am 12.09.2024 startete das Forschungsschiff SONNE zu einer Expedition in den südwestlichen Indischen Ozean. Vom 12. September bis zum 28. Oktober 2024 wird ein Team von 25 Wissenschaftler:innen unter der Leitung von PD Dr. Jör

Expedition SO307 investigates the geology and biology of the Madagascar Ridge On 12 September 2024, the research vessel SONNE set off on an expedition to the southwestern Indian Ocean. From 12 September to 28 October 2024, a team of 25 scientists led by PD Dr Jörg Geldmacher from the GEOMAR Helmholtz Centre for Ocean Research Kiel will explore the seabed south of Madagascar. Expedition SO307 will focus on geological and biological investigations to expand our understanding of the geology and biology of the seabed and seawater south of Madagascar.

The seabed is anything but flat - fascinating landscapes with high mountains, deep trenches and entire underwater mountains are hidden beneath the surface. And there are also plateaus - extensive, relatively flat areas that rise well above the ocean floor. Between Madagascar and Antarctica lies a striking example of such an oceanic plateau: the Madagascar Ridge. A team of 25 researchers is travelling there today on board the ship SONNE to solve a geoscientific mystery: During the SO307 MADAGASCAR/INDICOM expedition, one of the questions being addressed is when and how the Madagascar Ridge was formed.

The formation of the Madagascar Ridge: three hypotheses

For a long time, the theory was that the ridge was of volcanic origin. A so-called hotspot (mantle plume) could have pushed hot rock upwards from the earth's interior, where it emerged as molten rock and solidified into basalt. But there are also two other theories: It is possible that the elevation - like the island of Madagascar itself - is a remnant of the primeval large continent of Gondwana. This would mean that it consists of strongly stretched continental crust. Another, more recent theory assumes that the ridge was formed by the bulging of rock from the Earth's mantle, which became less dense as a result of earlier, massive melting events.

To test these theories, the research team will take rock samples directly from the Madagascar Ridge and the neighbouring mid-ocean ridge during the expedition. These samples can provide information about the composition, age and chemical properties of the ridge. ‘If we find basalt, this indicates a volcanic origin,’ says cruise leader Dr Jörg Geldmacher, marine geologist at the GEOMAR Helmholtz Centre for Ocean Research Kiel, ’but if we find mantle rock, this would confirm the theory of a bulging mantle. Both would be exciting.’ 

Biological diversity and material turnover in the deep sea

In addition to geological research, the biology of the seabed is also being investigated. Under the leadership of Professor Dr Carsten Lüter from the Museum für Naturkunde Berlin, the MADAGASCAR-BIO project focuses on researching the diversity of species in and on the seabed of the deep sea. The main aim is to identify previously unknown species and investigate their distribution. These investigations contribute to the long-term monitoring of deep-sea biodiversity and provide important insights into how oceanic elevations, such as the Madagascar Ridge, influence the distribution of species.

Another aim of the expedition is to better understand the cycle of organic material in the deep ocean. The INDICOM project, based at GEOMAR in the Marine Biogeochemistry research department led by Professor Dr Anja Engel, is investigating so-called gel particles, which are rich in carbohydrates and proteins and could take an important role in the microbial degradation of carbon. To this end, water samples are taken from different depths of the Indian Ocean using a crane water sampler in order to determine biogeochemical and biological parameters such as bacterial activity. This research is crucial for understanding carbon fluxes in the ocean and can contribute to improving climate models.

Keyfacts: 
Name: SONNE-Expedition SO307 MADAGASCAR/INDICOM
Coordinator: PD Dr. Jörg Geldmacher
Time: 12.09.2024 - 28.10.2024
Destination: Durban (Südafrika)
Shipping area: Southwest Indian Ocean

Funding:
The expedition is part of three research projects funded by the Federal Ministry of Education and Research (BMBF).

Links: 
Expedition SONNE SO307 via GEOMAR-Website 

Bildmaterial:
Image and pressmaterial: www.geomar.de/n9583