Correct Option
The correct option is (a).
Explanation
Igneous rocks are classified based on their place of origin into two main types: Intrusive (Plutonic) rocks, which form deep within the Earth, and Extrusive (Volcanic) rocks, which form on the surface.
Statement-wise Analysis
- Statement 1 is Correct: Extrusive igneous rocks are formed when molten magma erupts onto the Earth's surface as lava and solidifies. This process typically occurs during volcanic eruptions.
- Statement 2 is Incorrect: Due to exposure to the atmosphere, lava on the surface cools and solidifies rapidly. This rapid cooling prevents the growth of large crystals, resulting in a fine-grained or glassy structure. Large-grained structures are characteristic of intrusive rocks, which cool slowly at great depths.
- Statement 3 is Incorrect: Granite is a classic example of an intrusive igneous rock formed deep underground. A common example of an extrusive igneous rock is Basalt (found in the Deccan Traps).
Key Takeaway
Extrusive rocks (e.g., Basalt) form from the rapid cooling of lava on the surface and have a fine-grained texture. Intrusive rocks (e.g., Granite) form from the slow cooling of magma underground and have a coarse-grained texture.