Rocks

Lithification

Step 1: The question focuses on the specific process that turns loose sediment into solid rock. Step 2: When sediment layers accumulate, the weight of the upper layers puts pressure on lower layers, compressing them. Step 3: Water is squeezed out and the particles bond together to form hard rock — this process is called 'lithification'. Step 4: 'Diagenesis' refers to all physical and chemical changes during conversion of sediment to rock, while lithification is specifically the pressure-based hardening process. Step 5: Metamorphism involves heat and pressure changing existing rocks, and weathe

Dynamic metamorphism

Step 1: Metamorphism can be caused by heat, pressure, or both. Step 2: The question asks about the type caused by pressure alone. Step 3: Dynamic metamorphism is caused by pressure — for example, granite is converted into gneiss, and clay/shale becomes schist due to pressure at great depths. Step 4: Thermal (contact) metamorphism is caused by high temperatures, such as when magma comes in contact with surrounding rocks. Step 5: Regional metamorphism involves both heat and pressure over large areas, so it is not caused by pressure alone.

Regur

Step 1: Basalt is the main igneous rock of the Deccan Trap region. Step 2: Over millions of years, basalt undergoes weathering and breaks down. Step 3: The weathered product of basalt is a rich, dark-coloured soil called 'regur', also known as black cotton soil. Step 4: Regur is very fertile and ideal for cotton cultivation, hence it is also called 'black cotton soil'. Step 5: Loess is wind-deposited sediment, alluvium is river-deposited material, and laterite is a soil formed in hot, wet regions — none of these come from basalt weathering.

Marble

Step 1: The Taj Mahal is one of India's most famous monuments, located in Agra. Step 2: It is built from pure white marble, which is a metamorphic rock. Step 3: Marble is formed when limestone (a sedimentary rock) is subjected to high heat and pressure — this is thermal/contact metamorphism. Step 4: The white marble used for the Taj Mahal comes from Alwar, Ajmer, Jaipur, and Jodhpur districts of Rajasthan and near Jabalpur in Madhya Pradesh. Step 5: Slate, quartzite, and gneiss are all metamorphic rocks but are not used in the construction of the Taj Mahal.