Seafloor spreading hypothesis
Published on 31 Jan 2025
Proposed by Harry Hess. Based on extensive surveys, he made following observations,
Ocean floor features: Ocean floor have various diverse features, and the most remarkable one being Mid Oceanic Ridge (MOR).
Age of ocean crust: Nowhere older than mid-Mesozoic times
Rocks of MOR: Equidistant rocks from MOR shows similarities and age of rocks increases as moving away from crest.
Presences of trenches: Trenches in the ocean floor with high heat and thermal activity. There the sea mounts and guyots seems to have deformed and crushed.
He explained the above features with convectional current theory of Arthur Holmes.
Distribution of earthquake and rift valleys: At the locations of ascending and diverging mantle convection currents, there are the rift valleys and the MOR systems with volcanic eruptions.
Formation of faults: The diverging limbs stretch the ocean floors apart forming the normal fault.
Increasing age of ocean floor: Magma intrusion at mid-ocean ridges pushes older rocks apart, creating an older seafloor farther from the ridge, confirming seafloor spreading.
Consumption of earth crust: At the locations of descending mantle limbs, trenches are formed, where the ocean slabs are dragged into the mantle and destroyed.
Magnetic striping: Where alternate bands of reverse polarity rocks are found to be arranged on either side of the MOR system.
Hence, ocean floors are destructible and recyclable