Sea floor spreading is the process of new oceanic crust formation at mid-ocean ridges, where tectonic plates diverge and magma rises to fill the gap. This fundamental mechanism drives continental drift and reshapes Earth’s surface.

Mechanism of Sea Floor Spreading

1. Magma Ascension: At mid-ocean ridges, decompression melting produces magma that rises through the lithosphere, solidifying into new basaltic oceanic crust. Example – Mid-Atlantic Ridge creates symmetrical crust patterns.
2. Plate Divergence: New crust pushes existing plates apart at varying rates. Example – Mid-Atlantic Ridge spreads at 2-3 cm/year while East Pacific Rise moves at 10-15 cm/year.
3. Magnetic Striping: Earth’s magnetic field reversals create symmetrical bands of alternating polarity on the ocean floor. Example – Vine-Matthews hypothesis explains magnetic anomalies discovered in the 1960s.
4. Ridge Morphology: Spreading rate influences ridge characteristics – slow ridges form deep rift valleys, fast ridges create broad rises. Example – Slow Mid-Atlantic Ridge vs fast East Pacific Rise topography.
5. Transform Faults: Offset segments of mid-ocean ridges accommodate differential spreading rates. Example – Fracture zones in Atlantic Ocean connecting ridge segments.

The hypothesis of ‘Sea-Floor Spreading’ which proves the theory of Continental Drift was put forward jointly by Harry H. Hess and Robert Dietz in 1960.

The following three important facts were established by Hess:

1. The crust below the ocean floor was found to be only 6 to 7 km thick, whereas below the continental surface it was 30 to 40 km. 
2. Mid-Oceanic Ridges were present in all the oceans.
3. The ocean floors, nowhere, were found to be older than 135 million years, though the oceans are 3.9 billion 3900 million years old.

Evidence for Sea-Flooring Spreading

1. Occurrence of earthquakes along the crust of Mid-Oceanic Ridges.
2. The dearth of sediments at the crest of Mid-Oceanic Ridges and active volcanic islands like Iceland and Canary Islands.
3. Thickness of the sedimentary deposits increases away from the Mid-Oceanic Ridges.
4. There is reversal, in the main magnetic field of the earth known as ‘magnetic di-pole’ (magnetic field).
5. The normal and reverse magnetic anomalies are found in alternate manners on either side of the Mid-Oceanic Ridges. 

Contemporary Research and Evidence

1. Magma Supply Influence: Recent 2023 research shows magma supply affects seafloor morphology more than spreading rates. Higher supply creates longer, straighter abyssal hills.
2. Global Deceleration: Studies indicate seafloor spreading rates decreased over the past 19 million years, potentially reducing volcanic greenhouse gas emissions and altering ocean circulation.
3. SWOT Satellite Mapping: NASA’s SWOT satellite launched in December 2022 revolutionized seafloor mapping through precise water surface measurements, revealing underwater features with unprecedented detail.
4. Red Sea Evolution: Represents mature ocean basin with typical oceanic crust, demonstrating spreading system evolution over 13 million years of expansion.
5. Climate Implications: Seafloor spreading regulates volcanic outgassing, influencing atmospheric CO2 levels and long-term climate patterns through mantle-atmosphere carbon exchange.

Understanding sea floor spreading mechanisms enhances comprehension of plate tectonics, ocean basin formation, and earthquake-volcano distribution patterns, supporting modern geodynamic research and climate studies.