During mantle convection, heat from the earth's core causes material in the mantle to expand and move upward. when it reaches the top, it

The correct answer is - cools, moves to the side, and sinks, making a circular pattern.

The mantle convection is the one responsible for the movement of the tectonic plates, as well as for the destruction, recycling, and creating of new crust on the surface of the Earth.

Once the material from the mantle reaches the surface, it starts to fill in the gap and expand, thus creating new crust as it cools off, and it moves sideways, which pushes the older crust. The older crust sinks at other place where it subducts, thus is getting melted into the mantle and recycled, and over time, that recycled material will come on the surface again, thus creating a circular pattern.