For a long time, scientists thought that changes deep inside the Earth, like volcanic eruptions and tectonic plate movements, were the main drivers of surface events.
These events included mass extinctions, like the one 66 million years ago, and climate shifts between icy and warm periods.
However, a new study has uncovered an unexpected twist: the sun’s rays can also impact the Earth’s deep interior.
This groundbreaking study, published in Nature Communications, shows that solar radiation affects the Earth more deeply than previously thought. Solar radiation varies with latitude, creating temperature differences on the sea surface.
These differences affect marine life, which is rich in carbon. When oceanic plates subduct, or sink, into the Earth, they carry these carbon-rich organisms with them.
Researchers from the Institute of Geology and Geophysics at the Chinese Academy of Sciences found that this process significantly influences the redox state of arc magma. The redox state of arc magma is about the balance between reducing conditions (losing oxygen or gaining electrons) and oxidizing conditions (gaining oxygen or losing electrons) in magma formed in volcanic arcs.
Marine organisms act as a major reducer for the solid Earth, meaning they help balance this redox state.
The study collected thousands of magma samples to understand these variations globally. These samples are important for identifying metal ores like copper, tin, and lithium, which are essential for renewable energy technologies. By analyzing these samples, the researchers gained remarkable insights into how surface climate and deep Earth processes interact.
The researchers focused on the levels of vanadium and scandium in arc magma, using global geochemical data from the Cenozoic era and olivine-hosted melt inclusions. They discovered a pattern: less oxidized magma is found at lower latitudes, while more oxidized magma is found at higher latitudes.
“Previous studies only compared samples from the same longitudinal regions, such as the United States and Mexico, without finding significant differences. However, our samples from different latitudes showed varying redox responses, which sparked our curiosity. Trying to explain these differences led us to discover this unexpected pattern,” explained Wan Bo, a geologist and co-author of the study.
This discovery suggests that the surface climate has a direct influence on the deep Earth. Wan Bo emphasized that the Earth’s surface environment and climate have a significant impact on the deep interior of the planet.
Further evidence came from studies of the seafloor, showing more reduced carbon deposits at lower latitudes. This carbon interacts with sulfur to form sulfide, which is then transported into the mantle, contributing to the observed redox pattern.
“The observed pattern shows a strong link between the surface environment and the redox state of the deep Earth, providing new directions for exploring the resources and environmental impacts of subduction systems at different latitudes,” said Hu Fangyang, the study’s corresponding author.
While these results are compelling, the researchers acknowledge the need for more extensive data from global marine and subducted sediments. This study opens new avenues for scientific exploration, revealing how the sun’s influence penetrates deep into the Earth.
