what is the importance of magnetic reversals to the theory of plate tectonics? This is a topic that many people are looking for. bluevelvetrestaurant.com is a channel providing useful information about learning, life, digital marketing and online courses …. it will help you have an overview and solid multi-faceted knowledge . Today, bluevelvetrestaurant.com would like to introduce to you Magnetic Reversals and Sea Floor Spreading. Following along are instructions in the video below:
Everyone were going to talk about the earths magnetic field. And how the the reversals in the earths magnetic field revealed that seafloor spreading is happening. Thes magnetic field creates lines of invisible force that you cant see.
But that your compass needle senses and the reason your needle points north is that these field lines emerge from the south magnetic pole and wrap around the earth and point toward the north magnetic pole now we know that the earths magnetic field has actually reversed flipped around so that these arrows would all point. The other direction coming out of the north pole and pointing into the south pole and these are called magnetic reversals. They happen every few million years.
The earths magnetic field flips back and forth through time the reason. We know this is from lava flows like this lava flow on hawaii. When lava flows out of the earth.
Theres little magnetic minerals in the lava. And they line up with the magnetic field at the time and actually preserve like a tape recorder the direction of the earths magnetic field whichever way it was pointing either normal or reversed. So if we go look at a whole series of lava flows.
What well find if we sample through the lava layers into older and older. Layers well find some layers oriented with a magnetic. Fieldsay like today and other older layers that are reversed and then still older layers that are like today so through geologic time the earths magnetic field flips back and forth.
And we call. These magnetic polarity reversals. Now the way that this all relates to seafloor spreading can be realized by remembering that lava is pouring out of the earth at mid ocean ridges.
So i want you to imagine that were going to let this ocean basin spread. And were going to let the earths magnetic field flip back and forth as the ocean basin spreads. Remember that when the lava erupts and cools down.
It records. The direction of the magnetic field at the time whether its normal or reversed. So well start the animation here were going to start it at a time when the earths magnetic field is like today.
What we call normal polarity and as the seafloor spreads. Its all going to get polarized in the direction of the magnetic field shown by the blue part of the ocean floor. But now we have a reversal.
Happening and any new lava that erupts is going to get magnetized in the opposite direction. So you can see the little compass needles. Here are flipped showing us that all this new seafloor is recording.
The direction of the earths magnetic field at a time when it was reversed. Now well let the earths polarity flip again any new lava that forms is going to record the polarity of the earth at that time so what we see on the mid ocean ridges of the world today is a series of stripes symmetrical stripes on both sides of the ridges of seafloor rock. Thats magnetized in the same direction as the magnetic field today.
Then older rock. Thats reversed and still older rock. Thats back to normal this pattern is impossible to explain if seafloor spreading didnt actually happen and the earths magnetic field.
Didnt flip back and forth. So it constitutes some of the best evidence we have that the seafloor is actually spreading over geologic time. .
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