Basalt
Explanation
The Deccan Plateau is a large igneous province located in western and southern India. Its geological structure is primarily defined by the Deccan Traps, which are massive flood basalt layers formed by volcanic activity.
Detailed Analysis:
- Basalt (Correct): The Deccan Plateau was formed during the late Cretaceous period (approximately 66 million years ago) through a series of fissure eruptions. Huge volumes of lava flowed out and spread over vast areas. This lava cooled and solidified on the surface to form extrusive igneous rocks, specifically basalt. Basalt is fine-grained and dark-colored, characteristic of rapid cooling on the Earth's surface.
- Granite (Incorrect): Granite is an intrusive igneous rock, meaning it forms when magma cools slowly beneath the Earth's surface. While granite is found in parts of the Indian peninsular shield (e.g., Karnataka plateau), the Deccan Traps specifically are composed of basalt.
- Sandstone (Incorrect): Sandstone is a sedimentary rock formed by the accumulation of sand grains. It is not the primary constituent of the volcanic Deccan Plateau.
- Marble (Incorrect): Marble is a metamorphic rock formed from limestone under heat and pressure. It is not associated with the primary volcanic formation of the Deccan Traps.
Key Takeaway:
The Deccan Plateau is composed of flood basalts (Deccan Traps) formed by fissure volcanic eruptions, making Basalt the predominant rock type.