Researchers Discover Iron Isotope in Earth’s Core May Have Penetrated Lower Mantle Over Billions of Years
Deep within the Earth, a massive solid metal sphere is surrounded by a liquid iron and nickel layer, forming the two innermost layers of the planet. However, these layers are not always stable. A study published in the journal Nature Geoscience in 2020 reveals that iron isotopes may migrate into the mantle, the next geological layer of the Earth that begins at a depth of about 2,900 kilometers below the planet’s surface, according to IFL Science.
Simulation of Earth’s core. (Photo: Vadim Sadovski).
Collecting samples from the Earth’s mantle is extremely challenging due to its depth. Instead, scientists have discovered through experiments and geodynamic modeling how liquid iron alloys react under temperatures reaching up to 2,000 degrees Celsius and extreme pressures like those found in the Earth’s core.
Experiments demonstrate how iron isotopes migrate based on temperature differences, with heavier isotopes moving toward cooler areas. This effect likely causes material from the metallic core to infiltrate various regions at the lowest part of the mantle. If this is accurate, the research findings suggest that iron from the core has been leaking into the mantle for billions of years, according to Charles Lesher, the lead researcher of the 2020 study. Lesher is an emeritus professor of geology at the University of California, Davis, and a professor of petrology at Aarhus University in Denmark.
This is not the only area within the Earth that exhibits movement. Just as material moves from the core outward, other substances also travel from the surface to the inner layers. Other scientists have pointed out that water from the Earth’s surface is pushed into the mantle due to tectonic plate movements.
A 2014 study indicated that the transition zone of the mantle, approximately 410 to 660 kilometers deep, contains dense green rocks. These blue minerals hold water, but not in solid, liquid, or gaseous forms. Instead, they integrate water in a different molecular form that forms within the crystal structure.
However, ringwoodite (a blue rock where water is hidden) reveals the existence of a significant amount of water deep within the Earth. Researchers estimate that if just 1% of the rock in the mantle transition zone is water, the total amount would be nearly three times the water in all the oceans combined. In other words, a large portion of Earth’s water may lie within its mantle, trapped within the crystal structure of ringwoodite.
