Recent research published in Nature Geoscience suggests that lava from volcanic hotspots around the world, including Hawaii, Samoa, and Iceland, likely comes from a single, uniform reservoir within the Earth’s mantle.
This study shows that the Earth’s mantle is chemically more uniform than scientists previously believed. The distinct chemical characteristics of lavas only develop as they rise towards the surface.
Dr. Matthijs Smit, an associate professor and Canada Research Chair at the University of British Columbia’s Department of Earth, Ocean and Atmospheric Sciences, remarked, “This finding completely changes our perspective on hotspot lavas and the mantle itself. Much like humanity, Earth’s lavas represent a diverse population, all sharing a common origin, yet evolving differently in different locations.”
Direct sampling of the mantle is impossible, which complicates research. Instead, scientists perform geoscientific investigations by analyzing trace elements and isotopes in lava that erupts from mantle sources at oceanic volcanoes worldwide. Previous assumptions about the significant variances in lava composition – along with the belief that the isotope makeup of magma remains unchanged from its source to the surface – led to the idea that the mantle contains distinct reservoirs of different ages and origins. However, Dr. Smit and co-author Dr. Kooijman from the Swedish Museum of Natural History have made observations suggesting a different picture.
“By examining a specific group of elements, we identified the chemical influences of various processes that occur as magma moves to the surface,” explained Dr. Smit. “It turns out that all hotspot lavas actually originate from the same basic composition. The differences arise because the magmas interact with various types of rocks while they rise.”
The Earth’s mantle, a turbulent layer consisting of molten and semi-molten materials, makes up about 84% of the planet’s volume. It is positioned between the iron core and the Earth’s surface crust. When mantle-derived magma breaches the crust and erupts, it is referred to as lava.
Understanding the composition of the mantle is crucial for comprehending the formation of our planet, its evolution, and its behavior. This knowledge may also offer insights into the mechanisms of plate tectonics and the global cycle of elements.
In addition to providing new insights into oceanic hotspot lavas, this analysis found a notable connection to basaltic lavas on continents. These basaltic melts, which can include diamond-rich kimberlites, are fundamentally distinct from those at oceanic hotspots, yet they trace back to the same magma “ancestor.”
Dr. Smit called this finding a pivotal advancement in understanding Earth’s chemical evolution and global element cycles. “The mantle is not only more homogenous than previously thought, but it likely does not contain ‘primordial reservoirs’ – concepts that were once deemed necessary to explain prior data but didn’t quite fit with the idea of mantle convection.”
According to Dr. Kooijman, “This new model clarifies existing observations and opens the door to numerous new hypotheses for future global geochemical research.”
The research was financially supported by the National Science and Engineering Research Council of Canada.