Chapter 2: Structure of Earth
Questions included are
1. What are the various layers of Earth?
2. What is Crust?
3. Write the difference between Continental Crust and Oceanic crust?
4. Write short notes on Mantle?
5. Define Magma?
6. Write short notes on core?
7. Write difference between Rocks and minerals?
8. Define Ore?
9. Write difference between Intrusive Igneous rock and Extrusive Igneous rock?
10. Write major difference between Igneous, Sedimentary and Metamorphic rocks?
11. What are uses of Rocks and Minerals?
12. Define Rock Cycle?
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1. What are the various layers of Earth?
Earth is constituted by three layers.
Crust – Topmost layer.
Mantle = Middle layer.
Core = Inner most layer
2. What is Crust?
Crust is the thinnest Layer of the Earth
It is also called as Lithosphere.
There are two types of Crust. Continental Crust and Oceanic Crust.
Outer Crust has soil, that provides various minerals.
The main elements of crest are Silica (Si), Alumina (AI) Magnesium (Mg).
3. Write the difference between Continental Crust and Oceanic crust?
| Continental crust | Oceanic Crust |
| Continental Crust is below the landmass. | Oceanic Crust is below the ocean. |
| It is about 35km thick. | It is about 5km thick. |
| Main elements of continental crust is silica and aluminia. | Main elements of oceanic crust is Silica and Magnesium. |
| It is also called as Sial | It is also called as Sima |
4. Write short notes on Mantle?
- Mantle is present between crust and core
- It is about 2900 Km thick.
- It is made up of Magnesium, Iron and Silica.
- There are two layers of Mantle.
- Upper mantle average temperature is 890°C.
- Lower mantle average temperature is 2400°C.
5. Define Magma?
- Magma is present in lower mantle.
- It is the red molten Magma that comes out from interior of Earth through volcanoes in the form of lava.
- Lava is rich in metals and minerals.
6. Write short notes on core?
- Core is present below the mantle.
- It has a radius of 3500 Km.
- It is made up of heavy metals such as Nickel and Iron (Nife).
- There are two layers of core.
- Outer core has temperature 2200°c and Inner come 5000°C.
- The material inside the core is in molten form.
7. Write difference between Rocks and minerals?
| ROCKS | MINERALS |
| Material that forms the crust of Earth is called as Rock | Minerals are natural substances Found in the Earth’s oust and contain one or more elements. |
| Rocks do not have definite chemical composition | Minerals have definite chemical composition and physical properties |
| Rocks are hard and soft | Minerals may Non Metallic or Metallic |
| Ex: Granite, Marble, Clay,Chalk etc. | Ex: Coal, Natural gas, Petroleum. |
8. Define Ore?
A rock in which particular mineral is found in large percentage is called as Ore
Mining is done in areas where Ores are found.
9. Write difference between Intrusive Igneous rock and Extrusive Igneous rock?
| Intrusive Igneous Rock | Extrusive Igneous Rock |
| When magma cools below the surface of earth it is called as Intrusive Igneous rock. | When magma reaches the surface of Earth and cools down, it solidifies and form Extrusive Igneous Rock |
| It takes thousands of years to form and they develop into large crystals. | Crystals are small in size due to rapid cooling of lava. |
| Ex: Dolerite, Granite etc. | Ex: Basalt, Obsidian |
10. Write major difference between Igneous, Sedimentary and Metamorphic rocks?
| Igneous Rocks | Sedimentary Rocks | Metamorphic Rocks |
| Igneous rocks are formed by cooling of molten magma inside or on the Surface of Earth. | Sedimentary rocks are formed temperature by the sediments or layer of Plant, animal, remains deposited over large period of time hardened to form these rocks. | Under high temperature and pressure Igneous and sedimentary rock change their form to form metamorphic rocks. |
| These are formed either as large crystals or fine grained. | These are softer than Igneous rock and found in horizontal layers | These rocks are very hard, closed banded structures. |
| These rocks have metals and minerals. like Silver, Iron, gold etc. | These rocks have remains of plants and animals called as fossils. | These rocks do not have empty Space between them. |
11. What are uses of Rocks and Minerals?
- Rocks are used to make weapons and tools in olden days.
- Soil is formed from rocks.
- On the soil only we are constructing our houses, roads, buildings.
- Chemicals obtained from Sedimentary rocks are used to make fertilizers.
- Fossil fuel like Coal, Petroleum are the major Source of power.
12. Define Rock Cycle?
- A rock cycle is a process in which, under specific circumstances, one form of rock cycles repeatedly into a another type.
- With the help of erosion, deposition, pressure, melting, and cooling, older rocks are continuously changed into new ones.
- Rocks are created, destroyed, and then recreated in an eternal cycle. Igneous rocks are created when molten, heated lava cools.
- These igneous rocks are eroded and weathered by various weathering and erosional forces to produce sediments, which then transform into sedimentary rocks.
- Igneous and sedimentary rocks are transformed into metamorphic rocks under conditions of intense heat and pressure.
- The metamorphic and sedimentary rocks are buried once more and melt to create magma. On cooling, this magma again produces Igneous rocks.
- The Whole process is called as Rock cycle. The Scientific study of rocks is called as Petrology.
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