Short Answer:

Examples of igneous rock include granite, basalt, pumice, obsidian, and andesite. These rocks are classified into intrusive (plutonic) and extrusive (volcanic) igneous rocks. Intrusive rocks, like granite, form beneath the Earth’s surface, while extrusive rocks, like basalt and pumice, form from lava cooling quickly on the surface.

Igneous rocks form when molten magma or lava cools and solidifies. Intrusive rocks cool slowly, allowing large crystals to form, while extrusive rocks cool rapidly, resulting in fine-grained or glassy textures. These rocks are found in volcanic regions, mid-ocean ridges, and deep underground, shaping the Earth’s crust over millions of years.

Detailed Explanation:

Examples of Igneous Rock

Igneous rocks are formed from the cooling and solidification of magma or lava. They are divided into two main types based on their formation process:

1. Intrusive Igneous Rocks (Plutonic Rocks) – Form inside the Earth, cooling slowly and developing large crystals.
   • Examples:
     • Granite: A coarse-grained rock found in continental crust, used in construction.
     • Diorite: Similar to granite but darker in color, used in building materials.
     • Gabbro: A dense, dark rock, commonly found in oceanic crust.
2. Extrusive Igneous Rocks (Volcanic Rocks) – Form on the Earth’s surface when lava cools quickly.
   • Examples:
     • Basalt: A fine-grained rock that makes up most oceanic crust.
     • Pumice: A lightweight, porous rock formed from volcanic eruptions.
     • Obsidian: A glassy, black rock that forms when lava cools instantly.
     • Andesite: A medium-grained rock found in volcanic mountain ranges.

Each type of igneous rock has unique textures and mineral compositions, depending on how quickly it cooled and solidified.

How Igneous Rocks Form

Igneous rocks form through the cooling and crystallization of molten rock from the Earth’s interior. The formation process involves several steps:

1. Magma Generation:
   • Magma forms deep inside the Earth due to high temperature and pressure in the mantle.
   • Magma composition varies based on minerals present and plate tectonic settings.
2. Cooling and Crystallization:
   • Intrusive rocks: Magma cools slowly inside the Earth, forming large crystals (e.g., granite).
   • Extrusive rocks: Lava cools quickly on the surface, forming fine-grained or glassy textures (e.g., basalt, obsidian).
3. Solidification and Rock Formation:
   • As magma or lava cools completely, it hardens into igneous rock structures.
   • These rocks contribute to continental crust, ocean floors, and volcanic islands.

Uses and Importance of Igneous Rocks

• Construction Material: Granite and basalt are used in buildings, roads, and monuments.
• Soil Formation: Weathering of igneous rocks contributes to fertile soil.
• Volcanic Activity Indicators: Extrusive rocks help scientists study volcanic eruptions.
• Earth’s Crust Composition: Most oceanic and continental crust is made of igneous rocks.

Understanding igneous rock formation helps geologists explore Earth’s structure and history.

Conclusion

Examples of igneous rock include granite, basalt, pumice, obsidian, and andesite, classified as intrusive or extrusive based on their formation. Intrusive rocks cool slowly underground, forming large crystals, while extrusive rocks cool quickly on the surface, creating fine-grained or glassy textures. Igneous rocks play a vital role in Earth’s crust, volcanic activity, and construction materials.