- Definition: Metamorphic rocks are formed when pre-existing rocks undergo changes in their mineralogical composition and texture due to high temperatures, high pressures, or the presence of chemically active fluids.

- Formation: Metamorphic rocks are created through a process called metamorphism, which occurs deep within the Earth's crust due to tectonic activity, volcanic heat, or the intrusion of magma.

- Characteristics:

- Metamorphic rocks are characterized by their distinct mineral composition and texture, which result from the recrystallization of minerals in response to the changes in temperature and pressure.

- They often exhibit foliations or banding due to the alignment of minerals during metamorphism.

- Common examples of metamorphic rocks include slate, marble, gneiss, and schist.

Igneous Rocks:

- Definition: Igneous rocks are formed when magma or lava cools and solidifies. Magma is molten rock that originates from the Earth's interior, while lava is molten rock that reaches the Earth's surface through volcanic eruptions.

- Formation:

- Igneous rocks are classified into two main types based on their mode of formation:

- Plutonic igneous rocks are formed when magma cools slowly beneath the Earth's surface, allowing for the growth of larger crystals.

- Volcanic igneous rocks are formed when lava cools rapidly on the Earth's surface, resulting in the formation of fine-grained or glassy textures.

- Characteristics:

- Igneous rocks are primarily composed of minerals that crystallized directly from molten rock.

- They exhibit a wide range of textures, including crystalline, glassy, or porphyritic (containing larger crystals embedded in a finer-grained matrix).

- Common examples of igneous rocks include granite, basalt, obsidian, and pumice.

Comparison:

- Metamorphic rocks are formed through the transformation of pre-existing rocks, whereas igneous rocks are formed through the solidification of molten rock.

- Metamorphic rocks are typically formed at deeper levels within the Earth's crust, while igneous rocks can be formed at both deep and shallow levels, depending on whether they are plutonic or volcanic.

- Metamorphic rocks can exhibit foliated textures, while igneous rocks commonly have crystalline or glassy textures.

- Metamorphic rocks include minerals that are stable under relatively high temperatures and pressures, while igneous rocks contain minerals that crystallized from molten material.

In summary, metamorphic and igneous rocks differ in their formation processes, geological environments, textures, and mineral compositions, reflecting the distinct physical and chemical conditions under which they are created.