What is the main difference between the two layers of the mantle?

Answer 1

Chances are, you're on land right now. Scientists would say you are living on the sial. The sial is the part of the crust that is above water. It's a continental plate floating over the globe. Right underneath the sial is the sima. The sima is the layer of the Earth's crust that covers the entire planet. The sial is different in that it can begin and end where the plates do. You can think of the sima as the ocean floors. Under the sima is the mantle. When you consider the mantle is when you really start talking about the inner workings of the planet.

Answer 2

The main difference between the two layers of the mantle, the upper mantle and the lower mantle, is in their physical properties. The upper mantle is more rigid and behaves in a brittle manner, while the lower mantle is more ductile and capable of flowing like a slow-moving fluid over long periods of time. Additionally, the upper mantle is closer to the Earth's surface, while the lower mantle is located beneath the upper mantle.