What is the name of the process where a material that is weak enough to flow will rises when it is hot and sinks when it is cool causing a circulation cell?

Convection process

Explanation:

The process of convection is commonly takes place in the mantle portion of the earth and also at the atmosphere.

This process is usually defined as the process where the materials are heated at a high temperature, thereby making them less denser, and due to their low density they are gradually pushed upward into the upper zones. As the materials rises up, the density gradually increases due to the lowering of the temperature, and then the materials again sinks. This give rise to the formations of a circulating cell, which are commonly known as the convection cells.