If the oldest seafloor near the East coast of Brazil is 300Myr old, and the enti

Question

If the oldest seafloor near the East coast of Brazil is 300Myr old, and the entire Atlantic was formed by seafloor spreading at a constant rate, compute what is the rate of creation fof the enw seafloor near the mid-Atlnatic ridge in cm/yr? (the width of Atlantic ocean between Brazil and Sierra Leone is about 2848km).

b) In contrast, the oldest rocks found on the continents are about 4 billion years old. Explain why there is such a large difference in ages between oceanic and continental crust?

thanks..

Explanation / Answer

answer At a fast-spreading ridge (opening at up to 15 cm a year) the crust is smoother, with flat lavas flowing from fissures, than at a slow-spreading ridge (about 2 cm a year), where the median valley contains a chain of small volcanoes linked by fissure eruptions. The rate at which the mid-ocean ridge creates new material is known as the spreading rate, and is generally measured in mm/yr. The common subdivisions of spreading rate are fast, medium and slow, whose values are generally >100 mm/yr, ~60 mm/yr and

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