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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
What are minerals?
Distinguish between the following pair:
Degradation and aggradation
What are metamorphic rocks?
Give some examples of metamorphic rocks formed from sedimentary and igneous rocks.
Give reasons for the following
Extrusive rocks generally have small crystals.
Give reasons for the following
Silicates are the most common rock forming minerals.
Match the following:
| A. | Basalt | 1. | Anthracite |
| B. | Limestone | 2. | Extrusive igneous |
| C. | Coal | 3. | Metamorphic rock |
| D. | Gneiss | 4. | Sedimentary rock |
______ rocks are also called Primary rocks.
______ rocks are also known as stratified rocks.
Statement (1): Sedimentary rocks consist of many layers.
Statement (2): Sedimentary rocks are formed by the sediments deposited at different points of time.
