Rocks and Earth Materials

Igneous rocks are also called ‘primary rocks’ because they were the first ones to be formed. ‘Extrusive igneous rock’ is the name given to magma erupting and solidifying on reaching the earth’s surface. As magma cools down rapidly on reaching the earth’s surface, so these rocks are very fine-grained. Basalt is a typical example of extrusive igneous rocks.

The first three are sedimentary soils; quartzite is a metamorphic rock.

Availability of various rock forming elements (in percent) in earth’s crust (in % mass) is Oxygen – 46.6 Silicon – 27.7 Aluminium – 8.1 Iron – 5.0

Statement (1) is correct. Igneous rocks are the first one to be formed. All other rocks are formed by subsequent work of various rock forming processes and factors over these rocks. Thus, igneous rocks are also called parent rocks. Statement (2) is correct. Unlike sedimentary rocks, igneous rocks do not have any strata. Statement (4) is also correct. In the absence of pores in the igneous rocks, water does not penetrate in these rocks easily. Hence, igneous rocks are less affected by chemical weathering. Statement (3) is wrong. Sedimentary rocks are not the most widely distributed rocks on the earth’s surface.

Igneous rocks are divided into two main categories: plutonic rock and volcanic rock. Plutonic or intrusive rocks result when magma cools and crystallises slowly within the earth's crust. A common example of this type is granite. Volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta forming minerals such as pumice or basalt.

The scientific study of rocks is called petrology; pedology is the scientific study of soils.

Feldspars are a group of rock-forming tectosilicate (framework silicates) minerals that make up as much as 60% of the Earth's crust. Zeolites are framework silicates, with a completely linked framework of tetrahedra, each consisting of 4 O^2- surrounding a cation (usually Si⁴⁺ or Al³⁺).

It is correct.

Sandstone is a sedimentary rock composed of sand-sized mineral particles or rock fragments. It has significant porosity (typically 10-30%) and permeability due to the spaces between grains. In contrast, basalt, granite, and slate are much denser with very low porosity, making sandstone the most porous option.

Rocks are naturally occurring solid aggregates of minerals. Minerals are the homogenous substances (with definite chemical composition) that combine to form rocks. A single rock can contain one or multiple minerals.

Sedimentary rocks are formed from the accumulation of sediments in layers or beds over time. These layers often contain minerals that have settled out of water or air, leading to the occurrence of minerals in beds or layers. Examples include coal beds, iron ore bands, and limestone layers.

They contain oil and natural gas.

Coal and petroleum are fossil fuels that form from the accumulation and compression of organic matter over millions of years. This process occurs in sedimentary rocks, which are formed through the deposition and cementation of sediments. Metamorphic and igneous rocks like granite do not contain these fossil fuels.

Clay has the smallest particle size of all soil types, with particles less than 0.002mm in diameter. Particle size increases in the order: clay (<0.002mm) < silt (0.002-0.05mm) < sand (0.05-2mm) < gravel (>2mm). This gives clay its smooth texture when wet.

This is the correct answer. The peninsular plateau is composed of igneous and metamorphic rocks with gently rising hills and wide valleys.