Igneous rock forms through the cooling and solidification of molten rock material called magma or lava. The process can occur in different environments, leading to two main types of igneous rock: intrusive and extrusive.
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Intrusive Igneous Rock:
- Formation: This type forms from magma that cools and solidifies below the Earth's surface. Because it cools slowly, the crystals have more time to grow, resulting in larger, well-formed crystals.
- Examples: Granite and diorite.
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Extrusive Igneous Rock:
- Formation: This type is formed when lava erupts from a volcano or fissure and cools quickly upon exposure to the atmosphere or water. The rapid cooling results in smaller crystals or a glassy texture.
- Examples: Basalt and obsidian.
The composition of the original magma or lava, including the minerals present, also influences the type of igneous rock that forms. Factors such as the rate of cooling, the presence of gases, and the environment of eruption contribute to the physical and chemical properties of the resulting igneous rock.