Between Sial and Sima, Sima is heavier.
Understanding Sial and Sima
The Earth's crust is sometimes conceptually divided into two main layers based on their typical composition and density:
- Sial: This term is derived from the primary elements found in this layer: Silicon and Aluminium.
- Sima: This term comes from the primary elements: Silicon and Magnesium.
Density Comparison
According to the reference provided:
Sial means Silicon and Aluminium; it has a lighter density than the Sima (Silicon and Magnesium layer). Sial is lighter than Sima due to increased amount of aluminium, and decreased amount of iron and magnesium in it.
This clearly states that Sial is lighter than Sima, meaning Sima is heavier than Sial.
Why Sima is Heavier
The difference in density is attributed to their mineral composition. As the reference notes:
- Sial has a higher amount of aluminium.
- Sima has a relatively higher amount of iron and magnesium.
Elements like iron and magnesium are generally denser than aluminium. The presence of more iron and magnesium in the Sima layer contributes to its higher overall density compared to the Sial layer.
Quick Comparison Table
| Feature | Sial | Sima |
|---|---|---|
| Composition | Silicon and Aluminium | Silicon and Magnesium |
| Key Minerals | Aluminium, Silicates | Magnesium, Iron, Silicates |
| Density | Lighter | Heavier |
| Found In | Primarily Continental Crust | Primarily Oceanic Crust |
In Summary
The Sial layer, rich in silicon and aluminium, is less dense. The Sima layer, rich in silicon and magnesium (and also containing more iron), is denser. This density difference is why continental landmasses (largely composed of Sial-type rocks) effectively "float" on the denser, more fluid Sima-type material beneath.
