Earth Structure — Set 3
Geography · पृथ्वी की संरचना · Questions 21–30 of 50
Which theory explains the movement of Earth's lithospheric plates?
Correct Answer: C. Plate Tectonics
The theory of Plate Tectonics explains the movement of lithospheric plates. It builds upon the earlier concept of Continental Drift. It describes how plates move over the semi-fluid asthenosphere.
Which is the thinnest layer of the Earth?
Correct Answer: C. Crust
The Crust is the thinnest layer of the Earth. Its thickness ranges from about 5 km under oceans to 70 km under mountains. Compared to the mantle and core, it is like the skin of an apple.
What is the approximate radius of the Earth?
Correct Answer: B. 6,371 km
The approximate mean radius of the Earth is 6,371 kilometers. This distance is measured from the surface to the center of the core. The equatorial radius is slightly larger than the polar radius.
What is the average density of the Earth as a whole?
Correct Answer: A. 5.5 g/cm³
The average density of the Earth is approximately 5.5 g/cm³. The crust has a density of about 2.7-3.0 g/cm³, while the core is much denser at around 13 g/cm³. This makes Earth the densest planet in the Solar System.
The existence of a shadow zone for S-waves is the primary evidence for?
Correct Answer: C. A liquid Outer Core
The S-wave shadow zone exists because S-waves cannot travel through liquids. When seismic waves hit the liquid Outer Core, S-waves stop. This absence of S-waves on the opposite side of the globe confirms the liquid nature of the Outer Core.
Magma that erupts from volcanoes is primarily sourced from which layer?
Correct Answer: A. Asthenosphere
Magma is primarily sourced from the Asthenosphere in the upper mantle. Partial melting of rocks in this zone creates magma. This magma rises through the lithosphere to erupt as lava.
What is the most abundant element in the Earth's crust by weight?
Correct Answer: A. Oxygen
Oxygen is the most abundant element in the Earth's crust, making up about 46% by weight. Silicon is the second most abundant. Together, they form silicates, the most common mineral group.
What is the most abundant element in the Earth as a whole (entire planet)?
Correct Answer: D. Iron
Iron is the most abundant element in the Earth as a whole, constituting about 35% of the mass. Most of this iron resides in the core. Oxygen is the second most abundant element for the whole Earth.
The Inner Core stays solid despite temperatures exceeding 5000°C due to?
Correct Answer: C. Extreme Pressure
Extreme pressure keeps the Inner Core solid. The pressure is millions of times greater than atmospheric pressure at sea level. This raises the melting point of iron above the ambient temperature.
The Lithosphere rests and moves upon which layer?
Correct Answer: C. Asthenosphere
The tectonic plates of the Lithosphere rest and move upon the Asthenosphere. The Asthenosphere acts like a lubricant due to its plasticity. This interaction is central to plate tectonics.