About 2,890 kilometers beneath our feet lies a giant ball of liquid metal: the core of planet . Scientists use the waves created by earthquakes as a kind of ultrasound to "see" the shape and structure of the core. In doing so, they discovered a "doughnut" in the Earth's core.
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Using a new way to study these waves, scientists have made a surprising discovery: there is a large, doughnut-shaped region of the Earth's core around the equator, a few hundred kilometers thick, where seismic waves travel about 2% slower than in the rest of the core.
This region is believed to contain more lighter elements such as silicon and oxygen and may play a crucial role in the huge currents of liquid metal that flow through the core and create Earth's magnetic field . The results of the research were published in Science Advances .
The Earth's outer core has a radius of about 3,480 km, making it slightly larger than the planet Mars. It is composed mainly of iron and nickel, with some traces of lighter elements such as silicon, oxygen, sulfur, hydrogen , and carbon.
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The bottom of the outer core is hotter than the top, and the temperature difference causes the liquid metal to move like water in a boiling pot. This process is called thermal convection, and it is believed that the constant movement should mean that all the material in the outer core is well mixed and uniform.
But if everywhere in the outer core is filled with the same material, seismic waves should travel at roughly the same speed everywhere. So why do these waves slow down in the doughnut-shaped region found in the Earth's core?
The research suggests that there should be a higher concentration of light elements in this region. These may be released from the Earth's dense inner core into the outer core, where their buoyancy creates more convection.
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A more detailed view of the composition of the outer core – including the new doughnut of lighter elements – will help us better understand Earth's magnetic field. In particular, how the field changes its strength and direction over time is critical to life on Earth and the potential habitability of planets and exoplanets.
Source: sciencealert
