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How did seafloor spreading provide evidence for plate tectonics?
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geology
A rock formation called “faux amphibolite,” from the Nuvvuagittuq greenstone belt in northern Quebec, dated to 4.28 billion years ago.
Seafloor spreading provided critical evidence for plate tectonics by demonstrating that the ocean floor is dynamic rather than permanent, acting as a mechanism for the movement of continents.1
Key evidence includes:
- Age of Oceanic Crust: Samples show that the age of the oceanic crust increases with distance from the spreading centre. This confirms that new material is continuously created at mid-ocean ridges and pushed outward.12
- Marine Magnetic Anomalies: As magma cools at ridge crests, it records the polarity of Earth’s magnetic field. This creates symmetrical, parallel bands of magnetic anomalies on both sides of the ridge, providing a "tape recorder" of crustal movement over millions of years.13
- Sediment Thickness: The relative youth of marine sediments—none exceeding 200 million years—contradicts the older belief in the permanence of ocean basins, supporting the idea that the seafloor is constantly recycled.1
- Geological Activity: The presence of high heat flow, volcanic activity, and shallow earthquakes at ridge crests aligns with the upwelling of mantle material that drives plate divergence.124