Briefly explained the basis for how three major rock types are categorized
The correct answer and explanation is:
Rocks are classified into three major types based on their formation processes: igneous, sedimentary, and metamorphic.
- Igneous Rocks: These rocks form from the cooling and solidification of molten material, known as magma beneath the Earth’s surface or lava on the surface. The classification of igneous rocks is based on their mineral composition and texture, which is determined by how quickly they cool. Intrusive igneous rocks, like granite, cool slowly below the Earth’s surface and have large mineral crystals. Extrusive igneous rocks, like basalt, cool quickly on the surface, resulting in fine-grained textures. The ratio of silica and other minerals, such as iron and magnesium, further determines their categorization into felsic, intermediate, mafic, or ultramafic.
- Sedimentary Rocks: These rocks are formed from the accumulation and lithification of sediments, which are particles from other rocks, organic materials, or chemical precipitates. Sedimentary rocks can be classified into clastic, chemical, and organic types. Clastic sedimentary rocks, like sandstone, are formed from the compression of weathered rock fragments. Chemical sedimentary rocks, like limestone, form from evaporating water or precipitation. Organic sedimentary rocks, like coal, are formed from the remains of plants and animals. The characteristics of the sediments, including their size, composition, and origin, help in classifying the rocks.
- Metamorphic Rocks: These rocks are formed when existing rocks—either igneous, sedimentary, or other metamorphic rocks—are subjected to high pressure, temperature, or chemically active fluids. The heat and pressure cause mineral changes, leading to a new rock type with a different texture and structure. The degree of metamorphism helps classify these rocks. Foliated metamorphic rocks, such as slate, have mineral alignment due to pressure, while non-foliated rocks like marble do not exhibit this alignment. The original rock, known as the protolith, also influences the final characteristics.
Each rock type is categorized based on the processes involved in its formation, leading to distinct textures, mineral compositions, and structures.