Here's why:
* Intrusive: This term means the rock formed *within* the Earth's crust. Magma, molten rock, rises from the Earth's mantle and cools slowly underground.
* Igneous: This term simply means the rock formed from cooling magma or lava.
Examples of intrusive igneous rocks:
* Granite: A very common and hard rock often used in building materials.
* Diorite: A medium-grained rock with a distinctive speckled appearance.
* Gabbro: A dark-colored, coarse-grained rock.
Key Characteristics of Intrusive Igneous Rocks:
* Large crystals: Since magma cools slowly underground, the mineral crystals have time to grow large.
* Solid texture: The crystals interlock, giving the rock a solid and durable structure.
* No vesicles: Vesicles are air bubbles trapped in volcanic rocks. Intrusive rocks don't form under conditions where bubbles would be present.
