Earth is the planet on which we live. It is one of the eight planets in the Solar System and the only known celestial body in the Universe to support life. Earth was created over 4.5 billion years ago. During the early stage of the Earth, the entire planet was a ball of scorching matter. After it cooled down considerably, the ocean was formed, and the current layers of the solid Earth started to form. Earth is the third closest planet to the Sun. While large quantities of water can be seen in many celestial bodies in the Solar System, only the Earth possesses liquid surface water. Around 71% of the Earth’s surface is covered by polar ice, lakes, rivers, and oceans. The rest of the Earth’s surface is solid land, made up of islands and continents. The surface layer of the Earth is made of many slowly shifting tectonic plates — forming volcanoes, earthquakes, and mountain ranges. The liquid outer core produces the magnetic field that makes up the Earth’s magnetosphere, countering the dangerous solar winds.
The Earth’s structure is predominantly divided into four main components: the inner core, outer core, mantle, and crust. Every layer has its own distinct chemical composition and physical properties. The motion in the mantle is generated by fluctuations in heat from the core. It causes plates to shift slowly, which produces volcanic eruptions and earthquakes. Such natural phenomena physically alter our landscapes. Just like most known planets, our planet’s interior is layered clearly with distinct textures and properties. The entire internal structure is made of different sections, like the layers of an onion. The scientific analysis of the inner layers of the Earth is based on results generated with the help of seismic wave monitoring. Fundamentally, this involves detecting sound waves produced by earthquakes and analysing how going through various sections of the Earth forces them to slow down. The variations in seismic speed generate refraction, which is measured to find the variations in the layer’s density.
Important Layers of the Earth Questions with Answers
1) How can the Earth be divided?
The Earth is divided based on its mechanical and chemical properties. According to its mechanical properties, it can be divided into the inner core, outer core, mesospheric mantle, asthenosphere, and lithosphere. On the other hand, according to chemical properties, it can be divided into the core (subdivided into the inner core and outer core), the mantle (subdivided into lower mantle and upper mantle), and the crust. This is the most commonly used division. The Earth’s structure is predominantly divided into four main components: the inner core, outer core, mantle, and crust. Every layer has its own distinct chemical composition and physical properties.
2) Give a brief description about the evolution of the structure of the Earth.
The differentiation between the structural layers is predominantly due to phenomena that happened during the initial phases of Earth’s formation (about 4.5 billion years ago). At that time, melting would have forced denser materials to sink near the centre, while less-dense substances would have displaced to the crust. Thus, the core is considered to be largely made of iron and nickel, along with some less heavy elements.
3) What is meant by the crust of the Earth?
The crust is the outermost section of our planet, the hardened and cooled layer of the planet that extends in depth from around 5 km to 70 km. This structure makes up only 1% of the entire solid size of the blue planet, even though it constitutes the entire surface ( the ocean floor and the continents).
4) Explain the upper mantle.
The upper mantle ranges from the edge of the crust to a depth of around 410 km. The upper mantle is predominantly solid, but this mantle’s malleable sections create tectonic activity. Two sections of the upper mantle are frequently recognised as distinct areas of Earth’s structure: the asthenosphere and the lithosphere.
5) Explain the lower mantle.
The lower mantle lies between 660 kilometres and 2,891 kilometres in depth. This region’s temperature can reach over 4,000 °C at the boundary with the outer core, vastly greater than the melting point of mantle rocks. Interestingly, due to the extreme pressure applied to the mantle, viscosity and melting are very limited relative to the outer mantle. We know that it appears to be seismically homogeneous. Other than this, information about the lower mantle is very less when compared to the upper mantle.
6) Explain the outer core of the Earth.
The outer core is a fluid section about 2,260 km thick, made of mostly nickel and iron that exists above the planet’s inner core and under its mantle. The fluid outer core starts around 2,889 km under the Earth’s visible surface at the core-mantle frontier and ends 5,150 km under the Earth’s surface at the edge of the inner core boundary.
7) Explain the inner core of the Earth.
Just like the exterior core, the inner core layer is predominantly made of nickel and iron. The outer core has a radius of about 1,220 km. The density of the core extends from 12,600 kg/m3 to 13,000 kg/m3, which shows that there are a lot of heavy elements such as tungsten, palladium, platinum, silver, and gold. The average temperature of the Earth’s inner core is around 5,400 °C. The single reason why heavy metals can be in a solid state at such extreme temperatures is due to the pressure present there, which fluctuates from 330 gigapascals and 360 gigapascals.
8) When did different layers of the Earth form?
Earth was created over 4.5 billion years ago. During the early stage of the Earth, the entire planet was a ball of scorching matter. After it cooled down considerably, the ocean was formed, and the current layers of the solid Earth started to form.
9) What are the main constituents of the entire Earth?
Around 71% of the Earth’s surface is covered by polar ice, lakes, rivers, and oceans. The rest of the Earth’s surface is solid land, made up of islands and continents.
10) The surface layer of the Earth is made of many slowly shifting ______, forming volcanoes, earthquakes, and mountain ranges.
Answer: tectonic plates
Explanation: The surface layer of the Earth is made of many slowly shifting tectonic plates, forming volcanoes, earthquakes, and mountain ranges.
11) The scientific analysis of the interior structure of the Earth is based on results generated with the help of _____ wave monitoring.
Answer: seismic
Explanation: The scientific analysis of the interior structure of the Earth is based on results generated with the help of seismic wave monitoring.
12) The variations in seismic speed generate ________, which is measured to find the variations in each layer’s density.
Answer: refraction
Explanation: The variations in seismic speed generate refraction, which is measured to find the variations in each layer’s density.
13) The liquid outer core produces the magnetic field that makes up the Earth’s magnetosphere, countering the dangerous _____ winds.
Answer: solar
Explanation: The liquid outer core produces the magnetic field that makes up the Earth’s magnetosphere, countering the dangerous solar winds.
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Practice Questions
1) What is a mantle?
2) What is meant by the crust of the Earth?
3) What is the difference between the core and the mantle?
4) How are volcanoes formed?
5) Which is the hottest layer of the Earth?
6) How do earthquakes occur?
7) What is meant by tectonic plates?
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