Earth Structure — Set 4
Geography · पृथ्वी की संरचना · Questions 31–40 of 50
Approximately what percentage of Earth's total volume is occupied by the Mantle?
Correct Answer: A. 84%
The Mantle occupies about 84% of Earth's total volume. It is the most voluminous layer. In terms of mass, it makes up about 67% of the Earth.
What percentage of the Earth's volume does the Crust occupy?
Correct Answer: D. Less than 1%
The Crust occupies less than 1% of the Earth's volume. It is a very thin shell compared to the planet's size. Despite its small volume, it is the only layer we can directly explore.
The temperature at the center of the Earth is estimated to be approximately?
Correct Answer: C. 6,000°C
The temperature at the center of the Earth is estimated to be around 6,000°C. This is comparable to the surface temperature of the Sun. Heat is generated by pressure and radioactive decay.
Earth's magnetic field is generated by the 'Dynamo Effect' in which layer?
Correct Answer: D. Outer Core
The magnetic field is generated in the liquid Outer Core. Convection currents of molten iron create electric currents. These electric currents produce the magnetic field (Geodynamo).
Which discontinuity separates the Outer Core from the Inner Core?
Correct Answer: A. Lehmann
The Lehmann Discontinuity separates the Outer Core and the Inner Core. It marks the transition from liquid to solid iron. It is located at a depth of about 5,150 km.
The Mantle extends to a depth of approximately?
Correct Answer: D. 2,900 km
The Mantle extends to a depth of approximately 2,900 km. This depth marks the boundary with the liquid Outer Core (Gutenberg Discontinuity). The mantle is divided into upper and lower sections.
What is the average density of the Earth's crust?
Correct Answer: B. 2.7 to 3.0 g/cm³
The average density of the crust is about 2.7 to 3.0 g/cm³. Continental crust is lighter (~2.7) compared to oceanic crust (~3.0). This low density is why it forms the surface layer.
What is the approximate density of the Earth's Core?
Correct Answer: B. 13.0 g/cm³
The density of the Core ranges from about 9.9 to 13.0 g/cm³. The high density is due to the presence of heavy metals like iron and nickel under extreme pressure. The center is the densest point.
Which chemical compound is the most common constituent of both SIAL and SIMA?
Correct Answer: A. Silica
Silica (Silicon Dioxide) is the common constituent. SIAL is Silica + Aluminum, and SIMA is Silica + Magnesium. Silicate minerals make up the vast majority of the Earth's crust.
Which of the following is considered a 'Direct Source' of information about Earth's interior?
Correct Answer: A. Volcanic eruptions
Volcanic eruptions are a direct source of information. Magma brings material from the deep interior to the surface for analysis. Drilling projects are another direct source, though limited in depth.