Privileged Planet: Inner inner core (Introduction)

by David Turell , Wednesday, February 22, 2023, 15:23 (430 days ago) @ David Turell

New seismic study, we have an iron core inside the inner core:

https://www.sciencealert.com/after-a-20-year-search-scientists-have-finally-found-earth...

"A new analysis of Earth's innards suggests the presence of an inner core within the inner core – a dense ball of iron at the very center of our planet.

"This could reveal some previously unknown details about the history of Earth's formation and evolution, suggesting a significant global event early in our planet's history.

"Earth's interior structure consists of a series of concentric layers, from the crust to the core. At the very center, with a radius of about 1,227 kilometers (762 miles) is the inner core – the densest part of our planet, a solid ball mostly composed of iron and nickel, comprising less than 1 percent of Earth's volume.

"This inner core is like a time capsule of Earth's history.

"As the inner core grows, the solidification process releases heat and light that drives convection in the outer liquid core – the engine that powers the dynamo that converts kinetic energy into magnetic energy and maintains Earth's global magnetic field. That magnetic field is thought to keep harmful radiation out, and the atmosphere in, allowing life to thrive.

"Changes in the inner core could thus trigger changes in the dynamo, which in turn could have implications for Earth's habitability over time.

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"'This study uses the ever-growing global seismograph network to produce global stacks for some significant seismic events individually," they write in their paper.

"'This study reports a previously unobserved and unutilized class of seismological observations of reverberating waves through the bulk of the Earth along its diameter up to five times … To our knowledge, reverberations from more than two passages are hitherto unreported in the seismological literature."

***

"By stacking the data – adding a collection of seismic signals together into a single trace – Phạm and Tkalčić were able to amplify the signal from several major seismic events, thus breaking this record. For the first time, they identified three-, four-, and five-fold seismic reverberations, which in turn allowed a more detailed probe of the inner core than previously achieved.

"The different travel times of pairs of waves inferred the presence of the innermost inner core no wider than 650 kilometers (404 miles) across, made of dense iron. This structure could be the result of a fundamental change in the growth of the inner core at some point in Earth's past."

Comment: it is like pealing an onion. The finding gives an even clearer picture of how our protective magnetic field is generated.