Igneous rock

Definition

Igneous rock is a type of rock formed from the cooling and solidification of molten magma or lava. This process can occur beneath the Earth's surface, resulting in intrusive igneous rocks, or on the surface following volcanic eruptions, leading to extrusive igneous rocks. Understanding igneous rocks is crucial for comprehending geological processes, especially in relation to mountain formation at convergent boundaries, where tectonic plates collide, and magma is generated.

5 Must Know Facts For Your Next Test

1. Intrusive igneous rocks form from slow-cooling magma beneath the Earth's surface, leading to larger crystal sizes, while extrusive igneous rocks form from rapid cooling of lava at the surface, resulting in smaller crystals.
2. Common examples of intrusive igneous rocks include granite and diorite, while basalt and pumice are typical examples of extrusive igneous rocks.
3. At convergent boundaries, subduction leads to melting of the descending plate, which generates magma that can rise and form igneous rock.
4. The formation of igneous rocks at convergent boundaries often contributes to mountain building and volcanic activity in those regions.
5. The texture of igneous rock can vary widely based on the cooling rate and environment, influencing properties like porosity and mineral composition.

Review Questions

• How does the cooling process of magma differ between intrusive and extrusive igneous rocks, and what implications does this have for their physical characteristics?
  • The cooling process of magma differs significantly between intrusive and extrusive igneous rocks. Intrusive igneous rocks cool slowly beneath the Earth's surface, allowing larger crystals to form, resulting in a coarse texture. In contrast, extrusive igneous rocks cool rapidly on the Earth's surface after a volcanic eruption, leading to smaller crystals and a fine-grained texture. This difference in cooling rates directly impacts the mineral composition and overall appearance of these rocks.
• Discuss the role of subduction zones in the formation of igneous rocks and how this relates to mountain ranges created at convergent boundaries.
  • Subduction zones play a crucial role in forming igneous rocks as one tectonic plate is forced beneath another. This process generates magma through melting due to increased pressure and temperature. The rising magma can lead to volcanic eruptions or solidify underground, creating new igneous rock formations. This activity not only contributes to the growth of mountain ranges at convergent boundaries but also affects local geology through volcanism and metamorphism.
• Evaluate the significance of understanding igneous rock formation in predicting geological hazards associated with convergent boundaries.
  • Understanding igneous rock formation is essential for predicting geological hazards at convergent boundaries. The processes involved in subduction and magma generation can lead to significant volcanic activity, earthquakes, and the formation of mountain ranges. By studying the characteristics and behavior of igneous rocks formed in these environments, geologists can assess potential risks such as volcanic eruptions and landslides. This knowledge aids in disaster preparedness and management efforts in regions susceptible to these hazards.

Related terms

Magma: Magma is molten rock located beneath the Earth's surface, which can cool and solidify to form igneous rock.

Lava: Lava is molten rock that reaches the Earth's surface during a volcanic eruption and can cool to form extrusive igneous rock.

Subduction Zone: A subduction zone is a region where one tectonic plate moves under another, often leading to the formation of magma and the creation of igneous rocks.