The main reason why the tectonic plates move is the conversational currents. There is magma between the upper mantle and the asthenosphere that heats up at the upper mantle. The weight is so small that the magma rises with the help of these conversational currents. When the magma has ascended towards the asthenosphere, it has nowhere to go so the magma lies along the asthenosphere. There the magma cools down again because the asthenosphere is colder than the upper mantle, which makes the magma heavier and goes back down to the upper mantle, where the magma heats up again and everything starts all over again and so it goes on over and over again. Scientists have concluded that the earth's gravity causes two other processes that also cause the tectonic plates to move.
Ridge push - in the spreading zones, the sides of the tiles are raised and slide to the side as in a slide.
Slab pull - when a plate is pulled down by gravity in a subduction zone like an anchor.
About 71 percent<span> of the Earth's surface is water-covered, and the oceans hold about </span>96.5 percent<span>of all Earth's water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers</span>
The ocean floor preserve evidence of past magnetic reversals because c) the ocean floor is uniformly old, preserving the earth's 4.6 billion history.
<h3 /><h3>What subjects need to be studied to study the earth's magnetism?</h3>
Paleomagnetism is the study of naturally occurring residual magnetism in rocks with the goal of understanding the strength and direction of the Earth's magnetic field in the geologic past and understanding the motion history of plates. Paleomagnetic fields have played a large role in confirming undersea propagation, through the discovery and understanding of seafloor anomalies. In the 1960s, geophysicists studied the magnetic properties of the ocean floor and began to discover some amazing properties.
The seabed has a system of linear magnetic anomalies in which a "band" has all its magnetic minerals oriented in the same way as the current magnetic field and the magnetic minerals in the bands alternating is oriented in the opposite direction. These bands are oriented parallel to the mid-ocean ridge system; where the ridges compensate for the transform error, the anomalies are also compensated. Symmetrical anomalies are found on either side of the ridge, and similar symmetry is found in ridges around the world.
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