Scientists have observed that earth's tectonic plates move in predictable directions. what is the cause of this observation?

Uniform temperature inside earth forces the plates move.

Explanation:

The movements carried out by the tectonic plates occur due to the high temperatures existing inside the Earth.

The Earth's crust is located on the mantle, a layer of Earth composed of magma. The intense heat causes the circular movement of the mantle in convection currents. This convective movement transfers heat from the core (the Earth's innermost layer) to the outermost layers, causing the plates to move, leading to the junction or separation of the continents.

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