Question.
Q1. Give an account of the different layers of the interior of the earth. (UPPSC 2017)
Q2. Analyze the structure of the earth's interior. ( UPPSC 2000)
Q3. Write short notes on the Interior of Earth. ( UPPSC 1996)
Q4. Highlight the internal structure of the earth on the basis of seismological evidence. ( UPPSC 1994)
Answer.
Our Earth has three distinct layers:
- Crust
- Mantle
- Core
Crust:
The crust is the outermost and thinnest layer of the Earth. It is in solid form and brittle in nature. The thickness of the crust is not the same everywhere, it varies from 5 km (average thickness of oceanic crust) to 70 km (mountainous areas of a continent such as the Himalayas). The crust is mainly composed of lighter materials such as silicon and aluminum, which is why it is also called sial (SiAl).
The crust makes up 1% of the total volume of the Earth.
The following are the primary chemical structures of the crust:
- Oxygen (the largest, it is about 46.6% by weight)
- Silicon (the second largest, 27.7% by weight)
- Aluminum (8.1%)
- Iron (5%)
Mantle:
- The mantle is the second layer of the Earth, the thickness of the mantle is about 2900 km.
- The mantle makes up 84% of the Earth's total volume.
- The Moho discontinuity separates the mantle from the crust.
- The mantle is also divided into two sub-layers—the upper mantle and the lower mantle.
- The upper mantle is also called the asthenosphere. It is in semi-liquid form. The asthenosphere is the source of magma for volcanoes.
- The crust and the asthenosphere are collectively known as the lithosphere. The thickness of the lithosphere varies from 10 to 200 km.
- The lower mantle extends beyond the asthenosphere and is in the solid part.
- Due to the uneven presence of radioactive elements in the mantle, many convection cells form in the lower mantle and are the major driving force of the displacement of tectonic plates (asthenospheric plates).
- The major elements of the mantle are silicon and magnesium.
Core:
- The core is the third layer of the Earth, it starts from about 2900 km above the Earth's surface, and the average thickness of the core is about 3500 km.
- The core is further divided into two parts - the outer core and the lower core.
- The Gutenberg discontinuity separates the outer core from the mantle.
- The outer core is in liquid form.
- The inner core is in solid form, this is because the pressure here is much higher than the temperature, which is why the material is found in the solid form here.
- The entire core is composed of two major elements—nickel (20%)—and ferrous (80%).
- The core makes up 15% of the Earth's total volume.
You may like also:
ConversionConversion EmoticonEmoticon