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प्रश्न
How are sedimentary rocks formed?
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उत्तर
Sedimentary rocks are formed from sediments accumulated over long periods, usually underwater on the floors of shallow seas, rivers, and lakes. These rocks are non-crystalline and are found in layers or strata and contain fossils. Conglomerate, sandstone, limestone, chalk, calcite, and dolomite are examples of sedimentary rocks. Sedimentary rocks are divided into various types depending on how they are formed.
- Mechanically formed sedimentary rocks :
These rocks have been formed by the accumulation of materials derived from other rocks which have been cemented together.
Examples – conglomerate (rounded fragments), breccia (angular fragments). - Organically formed sedimentary rocks :
These rocks have been formed by the accumulation of the remains of living organisms.
Examples – calcareous rocks such as limestone and chalk. - Chemically formed sedimentary rocks:
These rocks have been commonly formed by the process of evaporation of water containing salts in solution.
Examples – rock salt, gypsum, potash, nitrates, calcite, and dolomite.
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संबंधित प्रश्न
Fill in the blank
A category of rock which is formed by the alteration of the parent rock due to heat and pressure is called: ______________.
Classify the following rocks by selecting the correct option given below:
sandstone
Explain the structure of the earth’s interior?
Give two examples of sedimentary rocks.
Fill in the blanks
______ rocks are formed by the deposition of shells and skeletons of organism.
Give reasons for the following
Rocks are of great economic significance.
Lava comes out from a volcano.
Out of 2,000 different types, only ______ are the basic minerals commonly found all over the earth.
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 |
