According to the theory of plate tectonics, the distance between two continents on opposite sides of a mid-oceanic ridge will generally..

The plate will continue to move apart and the distance between two opposite sides will continue to increase very slowly.

Explanation:

The theory of plate tectonic also talks about how divergent boundaries occur. Divergence boundary usually occur between continental-continental plate or oceanic-oceanic plate.

According to the theory of plate tectonic, the opposite sides in a divergent boundary will continue to move apart from each other. The moving apart from each other creates a room for the introduction of molten magma to the surface of the earth. This magma after exposure to the earth surface, solidifies to form a new crust. The magma can be introduce through the mid oceanic ridge . Closer to the mid oceanic ridge much younger rocks are formed . As one move farther way from the mid oceanic ridges the rocks become older.

Generally, between two continents of opposite side the continents will continue moving apart  from each other and the distance between them will continue to increase creating a space for magma to migrate to the surface of the earth . New crust are formed in the process.

The picture above illustrate diverging boundary with the mid oceanic ridges.