Today we delved a little deeper into pole reversal and how it relates to the evidence for seafloor spreading and did an enrichment worksheet in class. The kids are picking this stuff up pretty fast. I also had them take some notes, which they balked at. It’s funny how much they hate to take notes! Here’s what they had to write down:
Magnetic Shift
Polar shift is easily confused with pole reversal, in which the Earth’s magnetic poles change places. Evidence for such reversals is abundant, locked in the iron oxides of ancient rocks, which aligned along the direction of magnetic north when they cooled. This alignment still occurs in some igneous rocks, such as when lava cools and crystallizes. Magnetic pole reversals occur irregularly (around every 300,000 years) and require thousands of years to complete. Some call the South Atlantic Anomaly — a trough in the Earth’s magnetic field near the coast of Brazil that enables cosmic rays and charged particles to delve lower than usual into the atmosphere — a harbinger of an upcoming pole reversal, due perhaps as soon as 2012. Scientists think it unlikely; even if it happened, they say, the results would not be catastrophic.
One would have thought I asked them to copy War and Peace. I might make this paragraph part or all of the next quiz.