Answer:
The convection current in the mantle are generated due to the heat radiated from the interior of the earth. This heat is produced from the radioactive element that are deep inside the earth's surface. Due to this heat, the magma near the mantle core boundary gets heated up, as a result of which the magma becomes less dense and slowly rises up towards the top portion of mantle. This magma when reaches the top portion, the temperature decreases and becomes dense. It then sinks. This continuous motion of magma is known as the convection current in the mantle.
In the oceans, the convection currents are generated when the water becomes less due to the increasing heat near the surface at the equatorial region. This warm water is then carried towards the polar region by the wind. This warm water when reaches the poles becomes denser and sinks due to its lower temperature at the poles. This denser water again flows from the poles to the equator at the bottom of the ocean. This motion of water between equator and poles forms a the convection current.
These convection currents are similar because they are responsible for the formation of the earth's surface.
The are differences between the convection current in the mantle and ocean. The convection current in the mantle can create or destroy the crust, whereas the convection in the oceans are not responsible for this.
