DMPQ- Explain the concept of sea floor spreading

Concept of sea floor spreading was given by Henry Hess which was crucial to establish the formation of different geological surface on the earth. The major findings were:

  • The crust below the ocean floor was found only 7-8 km thick.
  • The existence of mid Atlantic ridge was known, but it was found that mid oceanic ridgesare present in every ocean and they are subjected to earthquakes and volcaniceruptions.
  • The rocks of the ocean floor were found not older than the cretaceous period anywhere(about 200 million years).
  • The normal and reverse magnetic anomalies are found in alternate manner on eitherside of the mid- oceanic ridges.
  • The youngest crust is at the mid oceanic ridge. With increasing distance from thesecenters, earth’s surface is increasingly older. The oldest seafloor is found near Japan inwestern pacific called the Pigafetta basin.


On the basis of the above discoveries, Hess postulated that the ocean floor is moving. Thehot magma rises up along the mid oceanic ridges due to convection currents and the floormoves away on either side of the ridges and finally gets lost in the ocean trenches situatedalong the continental margins. It is through this process of spreading that the ocean floorhas been built. In other words, the ocean floor is relatively new feature which is constantlybeing built , regenerated , subjected to constant lateral spreading and finally is destroyed intrench systems and becomes re-incorporated in to the mantle.


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