Answer:
A) The process of how convection cells form in the Earth's mantle involves heat sources that cause magma to expand and rise. These heat sources are primarily associated with the decay of radioactive isotopes in the Earth's interior. The decay of elements like uranium, thorium, and potassium releases a significant amount of heat. This heat warms up the surrounding rock, causing it to become less dense and more buoyant. As the rock becomes less dense, it starts to rise towards the Earth's surface. This rising, less dense material is what we commonly refer to as magma.
B) The magma eventually cools and sinks due to the process of heat loss. As magma rises to shallower depths, it comes into contact with cooler rocks and surroundings. The heat from the magma is transferred to the surrounding rocks, causing the magma to lose some of its heat energy. As the magma loses heat, it starts to cool and become denser. The denser, cooler magma is more likely to sink back down into the mantle. This sinking motion completes the cycle of convection cells, where warmer, less dense material rises, cools and sinks, and is then reheated by the heat sources in the Earth's interior, restarting the process.
Step-by-step explanation:
This continuous cycle of heat transfer and movement of magma creates convection currents within the Earth's mantle, contributing to the movement of tectonic plates and various geological processes.