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?
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Rocks. There’s so to say tiny magnets in them. When this rock formed from cooled down lava, the tiny magnets aligned with the current magnetic field of the earth. By looking at the orientation of these tiny magnets and noticing a back and forth, it was deducted that the magnetic field flips. For determining the time frame, there’s statigraphy. Certain layers of rock are a certain age based on different properties like known fossilized species.
Solidified magma from the Mid-Atlantic Divide.
The North American and European continental plates are being pushed apart. The magma thrusting up between the two cools and turns to new rock. As the continents move further apart, more and more rock is formed in convey-belt fashion, creating a historical record
Frozen within the rock are magnetic particles oriented towards the pole. They are observed to point different directions, depending on the age of the rock.
So, pole reversals.
The ocean crust is a good one.
So Yknow how a long long time ago there was no Atlantic Ocean, and South America and Africa were touching?
Well, we know roughly how fast the Atlantic Ocean has grown, and as it grows more magma from the earths core rises up in the center and becomes new ocean crust.
Well, the magnetic field influences how the ferromagnetic Elements in the crust form crystals when solidifying from magma to rock.
So, using magnetometers we can “see” striped patterns where one stripe formed while the earths magnetic field was one way, and the other formed while the magnetic field was reversed. And by looking at how wide those stripes are and estimating how long each stripe took to form based on how quickly new crust is forming, we can estimate how much time there was between reversals based on those stripes.
This was actually discovered in large part by the US Navy, as they looked for technology to find submarines.
As they looked at patterns of magnetism across the Atlantic seafloor, they discovered patterns in the seafloor that showed magnetic reversals. These rocks were later age-dated to find the time line of the reversals. This also helped prove plate tectonic theory.
https://www.sciencenews.org/article/fluxgate-magnetometer-submarine-plate-tectonics
I remember learning about this in my college geology class. Good question – if this sort of question is frequent, go study geology, it’s fun, technical and you can make lots of $$! So cool how the spreading floor of the ocean tells us the answer.
Imagine squeezing toothpaste out in a line on the table as you spin the tube and you can see a spiral form. Every few inches you spin the tube the opposite direction and you notice the spirals on the toothpaste go in a different pattern.
The earth is squeezing out magma/lava like you were squeezing out toothpaste. The earth’s magnetic field puts a “twist” on the magma as it cools making it magnetic as well. There’s a magnetic pattern that changes every few hundred meters away from where the earth is squeezing out the magma. This is like you noticing the change in spirals to tell when you changed spinning the toothpaste tube.
People are forgetting to add that at places like the mid-Atlantic ocean, the make is welling up out of the earth and spreading away from a fault-line in the middle of the ocean. The magnetic field is frozen in stripes as the magma cools, kind of like a strip chart recording of the earths magnetic field as a function of time. Since the rate of spreading is known, we can tell how many years ago the magma cooled.
“Basically, scientists study rocks that act like magnetic time capsules to figure out when Earth’s magnetic field did a flip. They’ve seen a pattern where it happens every 200,000 to 300,000 years or so. It’s like Earth’s own magnetic history book!”
Is the flip sudden or gradual? What are the visible (e.g.compass) or noticeable effects of a flip? Do we know or can we calculate when the next flip will occur?
The answer lies in the alignment of magnetic poles in cooled magma. Carbon-date the rock (cooled magma), then look at the orientation of the poles. I highly recommend checking out Ancient Apocalypse on Netflix. There are some fascinating topics covered, including this process.
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