The correct Answer is A-1, B-2, C-3, D-4
Explanation
This question pertains to the classification and characteristics of intrusive igneous landforms, which are formed when magma solidifies beneath the Earth's surface. These landforms are distinguished by their shape, orientation, and relationship with the surrounding rock strata.
Statement-wise Analysis
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A. Lapolith - 1. Saucer shape, concave to the sky body
Correct. Lapoliths are large, saucer-shaped intrusive bodies that are concave upwards, meaning they are bowl-shaped with the open side facing the sky. They typically form when magma intrudes between sedimentary layers and sags downwards due to its weight.
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B. Phacolith - 2. Wavy mass of intrusive rocks found at the base of synclines
Correct. Phacoliths are lens-shaped or wavy masses of intrusive igneous rocks that occur along the crests of anticlines or in the troughs of synclines in folded rock strata. They conform to the folds of the country rock.
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C. Sill - 3. Thick horizontal deposits
Correct. Sills are intrusive igneous bodies that are concordant, meaning they intrude parallel to the bedding planes of the pre-existing country rock. They are typically tabular and can be thick or thin, extending horizontally.
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D. Dyke - 4. Wall-like structure perpendicular to the ground
Correct. Dykes are discordant intrusive igneous bodies, meaning they cut across the bedding planes or other structures of the country rock. They are typically wall-like or sheet-like and are often oriented vertically or steeply inclined.
Key Takeaway
Intrusive igneous landforms like lapoliths, phacoliths, sills, and dykes are differentiated by their distinct shapes, orientations (concordant or discordant), and their relationship with the surrounding rock strata.