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प्रश्न
How are igneous rocks formed?
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उत्तर
Igneous rocks are formed by the cooling and solidification of molten rock called magma, which lies beneath the earth’s crust. These rocks are crystalline and compact. They do not occur in layers or strata, nor do they contain fossils. The cooling and solidification may take place at some depth within the earth or at the surface. The molten magma that reaches the surface of the earth is called lava. Thus, there are two types of igneous rocks classified on the basis of their place of origin – intrusive rocks, which form at some depth in the earth’s crust and extrusive rocks which form at or near the surface of the earth.
संबंधित प्रश्न
How are sedimentary rocks formed?
Distinguish between the following pair:
Degradation and aggradation
State two points of distinction between rocks and minerals.
Name the rocks which are most widespread on the earth.
Name the types Sedimentary rocks based on agents of formation.
Distinguish between the following:
Acid Igneous Rocks and Basic Igneous Rocks.
Describe how igneous rocks are formed.
In what type of rocks do you find fossils and why?
What is meant by the term ‘metamorphism’?
Classify the following rock: Gypsum
Classify the following rock: Marble
Give one word for the following.
The lower part of ocean floor, comprising mainly of silica.
Give one word for the following.
The core of the earth occupied by rock in iron and nickel.
Give one word for the following.
Igneous rocks, which contain a high percentage of silica.
Give one term for the following statement:
Igneous rocks of deep seated origin.
Give one term for the following statement:
Sheet like body of igneous rock.
Give one term for the following statement:
Formed by evaporation in saline lakes.
Fossils are found in.
Chemical sedimentary rocks are found in the beds of reservoirs.
Igneous rocks are found in the regions of volcanoes.
Kola sample title is located in ______.
The word ‘Igneous’ is derived from the ______ word.
Distinguish between:
Internal Processes and External processes.
Igneous Rocks are ______ rocks.
Explain about Petrology.
The oldest sedimentary rocks of the world have been identified in ______.
Minerals exist in nature ¡n the form of ______ or ______.
Statement (1): Sedimentary rocks consist of many layers.
Statement (2): Sedimentary rocks are formed by the sediments deposited at different points of time.
Match the following:
| A. | Basalt | 1. | Anthracite |
| B. | Limestone | 2. | Extrusive igneous |
| C. | Coal | 3. | Metamorphic rock |
| D. | Gneiss | 4. | Sedimentary rock |
