Our planet’s magnetic field is what defends us and makes the Earth habitable by impeding dangerous high-energy particles from space, including from the Sun. The origins of this magnetic field are the heart of the middle of our planet. However, the Earth’s core is tough to analyze, mostly because it starts at a depth of approximately 2,900 kilometers, which makes it too deep to test it and directly study it. Still, a research team has discovered a way to get information about our planet’s mantle and core. The paper has been published in the journal Geochemical Perspective Letters.
Earth’s core is extremely hot
The heart is the most heated area of our planet, with the outer core attaining temperatures of over 5,000℃. This has to impact the overlying mantle, and it is thought that 50 percent of volcanic heat comes from within the core.
The matter of whether there is any transfer of solid material between the core and the mantle has been argued since decades. This recent study implies that some core material does send into the base of these mantle pens, and the core has been seeping this element for the last 2.5 billion years. The scientists found this by analyzing tiny variations in the ratio of isotopes of the element tungsten.
Hunting for tungsten isotopes
Tungsten (noted as W), as the base element has 74 protons. The element has numerous isotopes, including 182W, with 108 neutrons, and 184W, with 110 neutrons. These isotopes of tungsten can likely be the most conclusive tracers of the core material. This is because the mantle is thought to hold much higher 182W/184W ratios than the core.
However, the analysis needed to identify variations in tungsten isotopes is complicated, as the team is looking at differences in the 182W/184W ratio in parts per million and the denseness of tungsten in rocks is quite low, more precisely, tens of parts per billion.
Earth’s core leaks material into our planet’s mantle
The study depicts a significant change in the 182W/184W ratio of the coat during the planet’s lifetime. The difference in the rate suggests that tungsten from the core has been seeping into the mantle for a while now. Surprisingly, in Earth’s oldest volcanic rocks there is no substantial change in the mantle’s tungsten isotopes. This suggests that from 4.3 billion to 2.7 billion years ago, a bit or no material from the core was leaked into the upper mantle.
Then, in the following 2.5 billion years, the tungsten isotope composition of the mantle has critically changed. It is possible that a change in plate tectonics resulted in convective currents sufficiently prominent in the mantle that changed the tungsten isotopes of the modern rocks.
Why is there a leak?
Experiments suggest that an increase in oxygen concentration at the core-mantle limit could result in tungsten splitting from the core into the mantle. Besides, inner core solidification would also raise the oxygen concentration of the outer core. The study gave researchers a tracer that can be utilized to examine core-mantle interaction and the change in the internal movements of the Earth. This can help scientists understand how and when the magnetic field was started.
Bo has over six years experience as a teacher, advocate and speaker. He has a B.S. from Cornell University, and a Ph.D. in Human rights from Harvard University Graduate School.