Today in class we used a really cool (and expensive) program on the computer to measure how the magnetic field lets us know about sea floor spreading. Ms. Meyer set out aluminium bins filled with sand (and I think magnets) and we used a sensor to pick up the magnetism in the rocks and magnets and the sensor sent its reading to the computer where we graphed it. When the graph went negative on the y-axis, the magnetic field had switched - north was south and south was north - but when it was positive on the y-axis, the magnetic field was in the same position as it is currently - with north as north and south as south. Our graph went over the x-axis about 4 times. Paleomagnetism is linked with sea floor spreading in the way that when the lava comes up and cools, all the magnetic minerals in the lava cool in the direction that the current magnetic field is. The ridges in the ocean that are created by sea floor spreading have different polarities based on the current magnetic field when the cooled. We know that sea floor spreading is true because the different parts of the ridge must've been at the middle of the ridge when they cooled and since they aren't now, they must've moved. And how did they get there? Sea floor spreading!
We also got our rocks and minerals unit tests back!
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