(HS-ESS2-3) In the lower mantle and asthenosphere, the matter can be described as a fluid, viscous solid. What is happening to this material in the mantle during convection?

In the lower mantle and asthenosphere, the material behaves as a viscous solid, which means it can flow slowly over geological timescales. During convection in the mantle, heat from the Earth's core and lower mantle causes the material to become less dense and rise toward the surface. As this material rises, it cools and becomes denser, eventually sinking back down. This process creates convection currents within the mantle. The hot, less dense material rises, while the cooler, denser material sinks, creating a continuous cycle. These convection currents are responsible for driving plate tectonics, influencing volcanic activity, and contributing to the movement of the Earth's lithospheric plates. The slow, viscous flow of the mantle material allows for the gradual movement of these plates, which can lead to geological phenomena such as earthquakes and mountain building.