Types of Rock
The Correct Answer and Explanation is:
There are three main types of rocks: igneous, sedimentary, and metamorphic. Each type of rock forms under different conditions and has distinct characteristics.
- Igneous Rocks: These rocks form from the cooling and solidification of molten rock, either magma below the Earth’s surface or lava that has erupted from volcanoes. Igneous rocks are classified into two categories: intrusive (or plutonic) and extrusive (or volcanic). Intrusive igneous rocks, such as granite, form when magma cools slowly beneath the Earth’s surface, allowing large crystals to form. Extrusive igneous rocks, like basalt, form when lava cools quickly on the surface, resulting in smaller crystals.
- Sedimentary Rocks: These rocks form from the accumulation and compaction of sediments, which could be bits of rock, minerals, and organic material. Over time, these sediments are pressed together and cemented into solid rock. Sedimentary rocks are often layered and can contain fossils. Common examples include sandstone, limestone, and shale. These rocks are typically found in environments like rivers, lakes, or oceans, where sediments can accumulate over time.
- Metamorphic Rocks: These rocks form when pre-existing rocks (either igneous, sedimentary, or other metamorphic rocks) undergo changes due to high pressure, temperature, or chemical reactions deep within the Earth’s crust. This process, known as metamorphism, alters the mineral composition and structure of the original rock. Metamorphic rocks can be foliated, meaning they have a layered texture, or non-foliated, which means they lack such a structure. Examples of metamorphic rocks include marble (which forms from limestone) and schist.
Each type of rock plays a vital role in the rock cycle, a continuous process where rocks are constantly being formed, broken down, and transformed into new types.
