Exam Focus: Igneous Rock Statements
This solution analyzes the provided statements to identify the correct description of igneous rocks.
Analyzing Igneous Rock Statements
Let's evaluate each statement regarding igneous rocks:
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Statement 1: "When magma cools deep in the Earth's interior, it results in the formation of fine-grained igneous rocks."
Incorrect. Magma cooling slowly deep within the Earth forms intrusive igneous rocks, which are typically coarse-grained. Fine-grained rocks usually form from rapid cooling on the surface (extrusive).
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Statement 2: "Basalt is a type of intrusive igneous rock."
Incorrect. Basalt is a common example of an extrusive igneous rock, formed from lava cooling quickly on the Earth's surface.
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Statement 3: "Most of the minerals of igneous rocks are silicates."
Correct. Igneous rocks are derived from molten material (magma or lava). The Earth's crust and mantle are predominantly composed of silicate minerals (compounds of silicon and oxygen). Therefore, the minerals that crystallize from this molten material are primarily silicates (e.g., quartz, feldspar, mica, pyroxene, amphibole).
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Statement 4: "Extrusive igneous rocks often undergo lithification."
Incorrect. Extrusive igneous rocks form from lava cooling on the surface. Lithification is the process that converts sediments into sedimentary rock, not igneous rock.
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Statement 5: (Empty option)
Not applicable.
Conclusion on Igneous Rocks
Based on the analysis, the only correct statement is that the majority of minerals comprising igneous rocks belong to the silicate group.
Important Questions from Rocks and Soils
Which of the following statements with reference to Salt Weathering is/are correct? 1. Salt crystallisation is the most effective of all the salt weathering processes. 2. Salt crystal growth is more effective over sedimentary rocks as compared to igneous rocks.
Which of the following statements with reference to Salt Weathering is/are correct?
1. Salt crystallisation is the most effective of all the salt weathering processes.
2. Salt crystal growth is more effective over sedimentary rocks as compared to igneous rocks.- Consider the following statements regarding metamorphic rocks :
1. Ortho-metamorphic rocks are formed from igneous rocks.
2. Intense heat of the intruding magmas results in metamorphism of the surrounding rocks, a process known as dynamic metamorphism.
Which of the statements given above is/are correct ? - Which of the following statements about the Black Soils of India is/are correct ?
1. Black Soils cover most of the Deccan Plateau.
2. Also known as 'Regur', they are generally clayey, deep and impermeable.
3. Since they are impermeable, rainfed crops do not grow well in Black Soils.
Select the answer using the codes given below : - Loose sediments are transformed into sedimentary rocks by the process of
