Came across a (https://www.youtube.com/watch?v=g6thUIR3_rI) which describes Earth’s magnetic field having switched hundreds if not thousands of times during Earth’s 4.5 billion years.
So, how do we know thats a fact? What are scientists looking at that helped them determine this?
In: 2148
1) It doesn’t flip on intervals of 200ka (ka = kilo-annum = thousands of years) to 300ka. It is not periodic at all. It flips statistically randomly over durations as short as a few thousand years to millions. One of the longest periods was the Cretaceous Quiet Zone which lasted over 30 million years. To characterize the duration the best you can do is calculate an average with a wide variability. There’s a pretty decent overview on the [wikipedia page about geomagnetic reversals](https://en.wikipedia.org/wiki/Geomagnetic_reversal#).
2) We know about reversals from rocks that preserve the orientation of the former field in magnetic minerals that formed within the rock (e.g., the most obvious example is the mineral magnetite, which is an iron oxide mineral and quite common). For igneous (formerly molten) rocks that’s normally the time the melt cooled and crystallized, and for sedimentary rocks (made up of particles deposited on the surface of the Earth) it’s usually shortly after deposition.
There’s tiger stripes miles in width and thousands of miles long where freshly solidified unmagnetized rock is magnetized by the earths natural field. The rock is produced continuously, so when the field flips, the newer rocks are magnetized the opposite way from before, this making a boundary between one tiger stripe and the newest tiger stripe of magnetized rock
There are magnets in rocks and there are clocks in rocks. The magnets tell us which way the magnetic field was pointing…the clocks say when it was like that.
Look up the tennis racket effect.
In the 80s they thought the world would flip up side down. But the earth isn’t actually round so the racket effect doesn’t apply.
Theory or we can ask our great great great x127 grandparents, since they were here at the time. 🥴
Rocks in the earth were made and had metal in them. Metal being magnetic wanted to point the direction of the pole. So when they cooled it made lines of metal pointing to where the pole was. When we look at other rock samples the direction of the metal lines change. Newer rocks point opposite direction so we know they flipped
As a side note, I don’t really like to watch these kinds of videos because there is just something kind of off or odd about them. The narrator almost sounds like an AI bot at times.
The discovery of regular polarity reversals on Earth’s magnetic field was made through geological research and the study of magnetic minerals in rocks. Scientists observed that as lava or molten rock solidified, iron-rich minerals within it aligned with the prevailing magnetic field at the time. By examining rock layers of different ages, they noticed alternating patterns of magnetic alignment, indicating a flip in the Earth’s magnetic polarity over time. This phenomenon, known as geomagnetic polarity reversal, provided crucial evidence that the Earth’s magnetic field changes direction periodically.
I assume this has to do with the flow of metals inside the Earth‘s core, but do we know WHY this happens? 🤔
Would we feel it when it happens? Or be able to observe macroscopic manifestations?
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