Convection Current Theory, paleomagnetism
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H. Harry Hess proposed the theory of seafloor spreading in 1960. Hess used the sonar to survey the ocean floor and find the mid-Atlantic ridge, also known as the mid-ocean ridge.
Additionally, he discovered that the area close to the mid-Atlantic ridge had a higher temperature than the surface farther away.
He thought that the magma seeping out of the ridge was the cause of the high temperature. This theory on the shifting position of the earth's surface supports Alfred Wegener's 1912 Continental Drift Theory.
Theory of Convection Currents
The foundation of the Seafloor Spreading Theory is the Convection Current Theory.
Convection currents in the mantle could be possible, according to Arthur Holmes' 1930s discussion.
These currents are produced by the mantle's temperature fluctuations brought on by radioactive materials.
This theory states that convection currents originate in the mantle as a result of the extreme heat produced by radioactive materials in the mantle, which is located between 100 and 2900 km below the surface of the earth.
Oceanic ridges are created on the seafloor wherever the rising limbs of these currents converge, and trenches are created wherever the failing limbs of these currents meet, as a result of the lithospheric plates' convergence (tectonic plates).
Magma in the mantle moves, which causes movement in the lithospheric plates.
Paleomagnetism
The study of the earth's magnetic field as it is preserved in rocks, silt, or archeological artifacts is known as paleomagnetism.
Thus, it is possible to determine the polarity of the Earth's magnetic field and magnetic field reversals by examining rocks from various eras.
Basaltic rocks, which make up the majority of the ocean floor, are primarily low silica and iron-rich rocks created by underwater volcanic activity.
Magnetic minerals are present in basalt, and when the rock solidifies, these minerals align themselves with the magnetic field's direction.
This preserves a record of the orientation of the magnetic field at that particular moment.
Geological time has seen repeated alternating (geomagnetic reversal) of the earth's magnetic field orientation, as evidenced by paleomagnetic examinations of rocks.
The resurgence of the continental drift theory and its development into the ideas of plate tectonics and sea floor spreading were both influenced by paleomagnetism.
The areas along the mid-ocean ridges where the seafloor is spreading contain the unique record of the earth's magnetic field.
It is discovered that alternating magnetic rock stripes were flipped, with one stripe having normal polarity and the other reversed, by examining the paleomagnetic rocks on either side of the oceanic ridges.
Therefore, the most significant evidence supporting the idea of sea floor spreading is found in paleomagnetic rocks (paleo: signifying rocks) on each side of mid-ocean or submarine ridges.
Records of magnetic fields can also reveal information about the historical positions of tectonic plates.
The boundaries where the tectonic plates are diverging are known as oceanic ridges.
Magma was able to ascend to the surface and solidify into a long, thin strip of rock on either side of the fissure, or vent, that existed between the ridge and the plates.
Before magma solidifies on the marine crust, it takes on the polarity of Earth's geomagnetic field as it rises.
The hardened band of rock moves away from the vent (or ridge) when the oceanic plates are pulled apart by conventional currents, and a new band of rock forms where the previous one was a few million years later when the magnetic field was reversed. The result is this magnetic striping where the polarities of the neighboring rock bands are opposing.
The result of this repeated procedure is an alternating pattern of magnetic striping on the seafloor and a succession of narrow parallel rock bands on either side of the ridge.
