It is the thickest of all the layers.
Explanation
The internal structure of the Earth is divided into three main concentric layers based on chemical composition and physical properties: the Crust, the Mantle, and the Core. The Crust is the outermost solid shell of the Earth.
Option-wise Analysis
- It is the uppermost layer over the earth’s surface. is Correct: The crust is the uppermost layer of the Earth. It is a solid, brittle layer that forms the exterior surface of the planet.
- It is the thickest of all the layers. is Incorrect: The crust is the thinnest of all the layers, not the thickest. It constitutes less than 1% of the Earth's volume. In contrast, the Mantle extends to a depth of 2,900 km, and the Core has a radius of approximately 3,500 km.
- It is about 35 km on the continental masses. is Correct: The thickness of the crust varies significantly. The continental crust is thicker, with an average thickness of about 35 km, reaching up to 70 km in major mountain systems like the Himalayas.
- It is about 5 km on the ocean floors. is Correct: The oceanic crust is thinner and denser than the continental crust, with an average thickness of approximately 5 km.
Key Takeaway
The Earth's crust is the thinnest layer, comprising less than 1% of the Earth's total volume, while the Mantle and Core constitute the vast majority of the planet's mass and dimensions.