Igneous Rocks:
* Formation: Formed from the cooling and solidification of molten rock (magma or lava).
* Characteristics: Typically have a crystalline texture, may be coarse-grained (slow cooling) or fine-grained (rapid cooling). Examples: granite, basalt, obsidian.
Sedimentary Rocks:
* Formation: Formed from the accumulation and cementation of sediments (rock fragments, mineral grains, organic matter).
* Characteristics: Often layered, may contain fossils, typically porous. Examples: sandstone, limestone, shale.
Metamorphic Rocks:
* Formation: Formed when existing igneous, sedimentary, or even other metamorphic rocks are transformed by heat and pressure, often deep within the Earth's crust.
* Characteristics: Often have a layered or banded appearance, may contain distinctive minerals. Examples: marble, slate, gneiss.
Here's a table summarizing the key differences:
| Feature | Igneous Rocks | Sedimentary Rocks | Metamorphic Rocks |
|---|---|---|---|
| Formation | Cooling and solidification of molten rock | Accumulation and cementation of sediments | Transformation of existing rocks by heat and pressure |
| Texture | Crystalline, may be coarse or fine-grained | Layered, may contain fossils | Layered or banded |
| Examples | Granite, basalt, obsidian | Sandstone, limestone, shale | Marble, slate, gneiss |
Important Note: Rocks are constantly being recycled through the rock cycle. This means that an igneous rock can be weathered and eroded to form sediment, which can then be compacted and cemented to form sedimentary rock. This sedimentary rock can then be subjected to heat and pressure to become metamorphic rock. Finally, metamorphic rock can be melted and cooled to form igneous rock again, completing the cycle.
