A textbook-altering discovery of a nearly 400-mile-wide iron ball present as the innermost layer of the earth. called the innermost inner layer.
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Scientists have found proof of the presence of another layer inside our planet, the earth. Earlier this month, a study revealed that the earth might have begun spinning in the opposite direction. In the previous week, another study suggested the presence of another layer of superheated rock inside the earth.
Until now, it was known that the earth has a solid metallic ball mainly made of iron which is known as the inner core. A new study has found the presence of a solid metallic ball inside the inner core called the innermost inner core.
This study suggests that the earth is made up of five layers instead of four. This could give new insights into the history of the planet and how it was formed.
The study was conducted by the geologists of the Research School of Earth sciences, Australian National University (ANU), Canberra, Australia. It was published in Nature Communications.
Joanne Stephenson, a geophysicist at ANU, said that the study might result in the rewriting of the textbooks.
The suggestion of the presence of another layer inside the earth was first suggested about 20 years ago. The detection of the innermost core was done by using data sets that were collected for the measurement of seismic waves of earthquakes as those passed through the earth’s center.
In the published paper, the scientists have said that now several different lines of investigation have enough seismological evidence about the existence of the innermost inner core.
Detection
Seismic Waves
Seismic waves are vibrations that run along or within the surface of the earth through its inner layers, which results in the form of volcanoes, earthquakes, or by other means.
The seismic waves generated by the earthquakes that pass through the inner core are measured to find out about the core of the planet as mentioned earlier.
Probes are stationed around the planet; these record the wave signals. Data from existing probes were collected to measure the different arrival times of seismic waves created by the earthquake’s energy that traveled through the earth.
It was observed by researchers that the waves reverberate through the earth’s diameter up to five times. Previous studies have recorded just a single antipodal bounce. The waves traveled through the center of the earth and spit out on the globe’s opposite side, which was then triggered by the earthquake, known as an antipode. These waves then traveled back to the source of the quake.
B, C: Five times reverberating waves through the inside of the earth. Different anisotropy of the innermost inner layer of the earth is shown in image.
Image Source: Nature
Dr. Thanh-Son Pham, a postdoctoral fellow, seismologist, and co-author of the study at ANU said that the composition of the innermost inner layer and the previous layer to that is similar, that is, both are made up of iron-nickel alloy and this is why the layer was not detected earlier.
Furthermore, he added that its observation via direct reflections of seismic waves cannot be done because the transition from the innermost ball, which is solid, to the outer shell of the inner core, also solid, seems gradational rather than sharp.
A distinct anisotropy was observed by researchers by studying the seismic waves that traveled through the center of the earth in different directions.
Anisotropy
Anisotropy is the property used to describe the speed of the seismic waves traveling through the inner core in different directions. It depends upon the arrangement of iron atoms at high pressure or temperature, or the alignment of growing crystals.
The researchers found that the bouncing seismic waves probed the spots near the earth’s center repeatedly from different angles. The variation in travel time of seismic waves from different earthquakes was analyzed and it was found that the crystallized structure inside the inner core’s innermost region was different from the outer layer.
It is believed that this finding could give a better understanding of the magnetic field of the earth, its evolution, and its future. Further investigations may be done to analyze the layer’s radius, precise anisotropic properties, and the nature of the transition to the outer inner core.
