![]() ![]() The potential difference between the innermost metallic ball and the outer shell of the inner core is not in its chemical composition, like with some other Earth layers. ![]() By capturing them, we obtain an unparalleled sampling of the innermost inner core. It differs from previous studies because it uses seismic waves that bounce multiple times within Earth, along its diameter and through its centre. These new observations are exciting because they provide new probes from different angles of the centremost part of our planet.Ī critical advantage of our study was getting data from dense continental-scale networks (consisting of several hundred seismometers) installed around some of the largest quakes. Now, for the first time, we report observations of seismic waves originating from powerful earthquakes travelling back and forth from one side of the globe to the other up to five times like a ricochet. Several lines of evidence have confirmed its existence, including recent studies from our research group. With the limited data we do have from such antipode measurements, an internal metallic ball within the inner core – the innermost inner core – was hypothesised about 20 years ago, with an estimated radius of about 300km. To target this relatively small volume in the planet’s centre, seismometers often need to be positioned on the opposite side of the globe, the so-called antipode of an earthquake.īut that’s unlikely in practice because the antipodes of active earthquake zones are often in the ocean, where seismometers are expensive to install. Meanwhile, seismometers mainly exist on land.įurthermore, the inner core, which is one-fifth of Earth’s radius, accounts for less than 1% of Earth’s volume. Large earthquakes useful for our probes are confined near tectonic margins, such as the Ring of Fire surrounding the Pacific. However, unlike medical imaging, we do not have the luxury of having sources and receivers equally distributed around the body. Earthquakes are our sources, and seismometers recording ground motions or vibrations that move through Earth are our receivers. Like radiologists imaging a patient’s internal organs, seismologists use seismic waves from large earthquakes to study the deep interior of Earth. So, understanding the evolutionary history of our planet’s inner core and its connection with the geomagnetic field is relevant to understanding the timeline of life’s evolution on Earth’s surface. ![]() ![]() Without the shield it provides, life on Earth would not be possible in the form we know today. The magnetic field protects life on Earth from harmful cosmic radiation. In turn, this convection generates our planet’s geomagnetic field. As these materials solidify, heat is released and causes upward movement in the liquid layer – what’s known as a convection current. This is because the inner core grows outwards by solidifying materials from the liquid outer core. Studying Earth’s centre is not just a topic of academic curiosity, but something that sheds light on the very evolution of life on our planet’s surface. In a new study published today in Nature Communications, we provide further evidence for the existence of an “innermost inner core” – a distinct internal metallic ball embedded in the inner core like the most petite Russian nesting doll. NOT so long ago, Earth’s interior was thought to be made up of four layers: the crust, mantle, (liquid) outer core and (solid) inner core. Studying Earth’s centre is not just a topic of academic curiosity, but something that sheds light on the very evolution of life on our planet’s surface, write THANH-SON PHAM and HRVOJE TKAL Č IĆ. ![]()
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