What Are Isochrones?


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Shumaela Rana answered
The ages of the sea floors of the world's oceans are determined by the fossil and magnetic reversal data. Each magnetic reversal band represents a span of time that gives the age of the crust within the band.
"The boundaries between the bands are contours that connect rocks of equal age and are called isochrones". The isochrones show the time that has elapsed and therefore the amount of spreading that has occurred since the crustal rocks were injected as magma into a mid ocean rift. The sea floor becomes progressively older on both sides of the ridge rifts, where sea floor spreading originates. The more widely spaced isochrones signify the faster spreading rates and vice versa. For example the isochrones of the eastern Pacific are wider than those in the Atlantic means the sea floor spreading rate is faster in case of the eastern Pacific than the Atlantic. Because of the fact that each isochrone was at the plate boundary of separation at an earlier time, isochrones that are of the same age but on opposite sides of an ocean ridge can be brought together to show the positions of the plates and the configuration of the continents embedded in them as they were in the earlier time. For example, using the isochrones, geologists can reconstruct the opening of the Atlantic Ocean.

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