Which best compares earth crust and mantle
To compare the Earth's crust and mantle, we need to understand their characteristics and composition.
The Earth's crust is the outermost layer of the planet and is generally divided into two types: continental crust and oceanic crust. Continental crust is thicker and less dense than oceanic crust, consisting mainly of granitic rocks. On the other hand, oceanic crust is thinner and denser, primarily composed of basaltic rocks.
The Earth's mantle is located beneath the crust and makes up a significant portion of the planet's volume. It is divided into two main sections: the upper mantle and the lower mantle. The upper mantle is composed mainly of peridotite, a rock rich in minerals like olivine and pyroxene. The lower mantle is under immense pressure and heat, causing minerals to undergo structural changes.
Now, let's compare the crust and mantle in terms of thickness, composition, and physical properties:
1. Thickness: The Earth's crust varies in thickness, with continental crust ranging from approximately 20 to 70 kilometers and oceanic crust averaging around 7 kilometers. In contrast, the mantle extends for approximately 2,900 kilometers from the crust-mantle boundary to the outer core.
2. Composition: The crust is primarily composed of lighter, low-density rocks like granite (continental crust) and basalt (oceanic crust). In contrast, the mantle consists mainly of denser rocks like peridotite.
3. Physical Properties: The crust is relatively cooler and less dense compared to the mantle. It also experiences more surface interactions, leading to more significant variations in temperature and pressure. The mantle, being deeper within the Earth, is subject to higher temperatures and pressures, leading to more significant flow and convective movements.
In summary, the crust is the Earth's thin outer layer, while the mantle lies beneath it and extends much deeper. The crust is less dense and composed of different types of rocks, while the mantle is denser and primarily made up of peridotite.