Sea Floor Spreading And And Ocean Age

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Sea floor spreading and and ocean age.

Every once in a while the currents in the liquid core which create the earth s magnetic field reverse themselves. These age data also allow the rate of seafloor spreading to be determined and they show that rates vary from about 0 1 cm 0 04 inch per year to 17 cm 6 7 inches per year. This idea played a pivotal role in the development of the theory of plate tectonics which revolutionized geologic thought during the last quarter of the 20th century. This has happened many times throughout earth s history.

It is called a geomagnetic reversal. The magnetism of mid ocean ridges helped scientists first identify the process of seafloor spreading in the early 20th century. Seafloor spreading rates are much more rapid in the pacific ocean than in the atlantic and indian oceans. At a spreading center basaltic magma rises up the fractures and cools on the ocean floor to form new seabed.

For that geologists date and study continental crust. Hydrothermal vents are common at spreading centers. Since the oldest ocean crust is so much younger than the oldest continental crust scientists realized that seafloor was being destroyed in a relatively short time. At spreading rates of about 15 cm 6 inches per year the entire crust beneath the pacific ocean about 15 000 km 9 300 miles wide could be produced in 100 million years.

Ages for ocean floor between the oldest identified magnetic anomalies and continental crust are interpolated by geological estimates of the ages of passive continental margin segments. The oldest seafloor is near the edges of continents or deep sea trenches and is less than 180 million years old. Because of this correlation between age and subduction potential very little ocean floor is older than 125 million years and almost none of it is older than 200 million years. Seafloor spreading leads to the renewal of the ocean floor in every 200 million years a period of time for building a mid ocean ridge moving away across the ocean and subduction into a trench.

Scientists can determine the age of the seafloor by examining the changing magnetic field of our planet. The age spreading rate and asymmetry at each grid node is determined by linear interpolation between adjacent seafloor isochrons in the direction of spreading. Older rocks will be found farther away from the spreading zone while younger rocks will be found nearer to the spreading zone.