A team of French and Australian scientists believe that a new embryonic continent may have begun to form on the Kerguelen underwater plateau in the Indian Ocean. The hypothesis may help to better understand how magma has evolved over thousands of years.
From a geological point of view, it is the planet’s outer crust that distinguishes the continents from the oceans. The Earth’s oceanic layer is relatively thinner and is composed primarily of basalts that formed as a result of melting of Earth’s underlying mantle.
The continental crust is thicker and its granitic composition is the result of magma that evolved deep in our planet before solidifying. Said magma usually forms in subduction zones, that is, where two tectonic plates slide one on the other.
The new study published in the Terra Nova magazine provides evidence that embryonic continents could also form on oceanic plateaus such as those of the Kerguelen Islands. Formed by extensive basalt flows, the lining of these plateaus is abnormally thick compared to normal oceanic crust, suggest the researchers, led by the Toulouse Environmental Geosciences Laboratory.
They reached this conclusion after having studied geometry and internal structure of syenite – a kind of igneous plutonic rock – present in the solidified lava of the plateaus. Furthermore, the scientists were able to reconstruct their history and found that their samples closely resemble rocks extracted from a large number of magma intrusions into the continental crust.
Now they wonder if the intrusion of the syenite could point to the formation of a new continent. To answer this puzzle, the team is studying the chemical composition of the syenites. The results of this research will help to know its origin and understand how magma has evolved over thousands of years.