The eastward flow of the equatorial counter-current is primarily explained by the Earth`s rotation on its axis. This phenomenon, known as the Coriolis effect, causes moving objects, including ocean currents, to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. In the equatorial region, where the trade winds from the northeast and southeast converge, the Coriolis effect influences the direction of the currents. The Coriolis effect deflects the equatorial currents slightly poleward, creating a narrow eastward-flowing counter-current between the equatorial currents. Therefore, the Earth`s rotation on its axis is the main factor that accounts for the eastward flow of the equatorial counter-current.