Q:

What is the theory of seafloor spreading?

A:

Seafloor spreading is an oceanic process involving the formation of new oceanic crust through the solidification of basaltic magma at mid-ocean ridges. This process is a partial explanation for the process of Continental Drift.

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The magma that forms these new plates emerges when oceanic plates part from one another due to climatic or geological stresses. Convection currents in the relatively weak and flexible upper mantle of Earth's crust are the driving cause of these stresses.

Rifts have the following features:

  • Most rift systems are triple-armed, meaning three fissures form.
  • Rifts begin as domes created by rising heat and pressure in the Earth's mantle.
  • Three-armed rifts spread until one arm dies and the remaining two extend to the extent of the crust's plasticity.

Full developed rifts can split continental masses from one another and eventually develop into new oceanic basins which will in time form oceans. Arabia and Africa are in the process of splitting due to the formation of just such a rift, but they will not complete this process for millions of years.

Existing rifts on the ocean floor map out the progress of continental masses and sea floor during the millennia of Earth's existence. Africa's Western coast is home to just such a concluded rift. The Earth is constantly being reshaped by this process.

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Related Questions

  • Q:

    How do hydrothermal vents form?

    A:

    Hydrothermal vents form in mid-ocean ridges where tectonic plates are spreading apart and seawater percolates down fissures and is heated by hot magma. They were first seen in 1977 in the Galapagos Islands by scientists who discovered that bacteria were converting toxic vent materials into usable energy for other organisms that had never been seen before.

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  • Q:

    What is the evidence for sea floor spreading?

    A:

    Encyclopædia Britannica states that many pieces of evidence support the sea floor spreading theory of plate tectonics, including increased heat flow along mid-ocean ridges, geomagnetic anomalies near ocean ridges, thickness of marine sediments and age of sediments. Sea floor spreading was first proposed by geophysicist Harry Hess in 1960 after reviewing submarine data. The theory is the basis for modern plate tectonics that states plates in the Earth's crust move.

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  • Q:

    What evidence is there of the continental drift theory?

    A:

    According to National Geographic, sea floor spreading and plate tectonics indicate that the continents do move or shift, which supports continental drift theory. Fossils of the Mesosaurus, an ancient freshwater reptile found in the southern parts of South America and Africa, also indicate that the two continents could have once been one solid continent that drifted apart, since the reptile could not have swum across the ocean.

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  • Q:

    What does the theory of evolution state?

    A:

    Darwin's theory of evolution states that evolution happens by natural selection. According to the evolutionary theory, the genes that allow a species to thrive are passed down from parent to offspring. Individuals of a particular species often have a wide range of variation and this variation occurs because of a difference in genes. Any individuals that possess the characteristics that will help the species thrive and survive in a particular environment will be the ones to reproduce.

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