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Key Information

Igneous Rocks

Type Formed from Cooling Magma
Area Small amounts on the surface, or crust, of the Earth, the rest underground or at the bottom of the oceans
Examples Granite, gabbro, diorite (intrusive), andesite, tuff, basalt, obsidian (extrusive)

Learning Point

  • Igneous rocks (or volcanic rocks) are the building blocks for most other rock types, coming from the molten magma of the Earth. Depending on where it forms, either on the surface, or deep underground, affects the texture of the rock. Often they form various crystalline patterns. Just 15% of the surface of the Earth is volcanic rock.

Project

  • Draw some igneous rocks from near where you live.
  • Overview
  • Coarse Grain
  • Fine Grain
Igneous Rocks
Nmnogueira, CC BY-SA 3.0, via Wikimedia Commons
Coarse Grain Igneous Rock - Granite
Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster). [1], Public domain, via Wikimedia Commons
Fine Grain Igneous Rocks - Basalt
B.W. Hallett, V. F. Paskevich, L.J. Poppe, S.G. Brand, and D.S. Blackwood, Public domain, via Wikimedia Commons

Fun Facts

  • Igneous rocks are divided into two basic categories, intrusive and extrusive.
  • Intrusive rocks are more grainy, where as extrusive rocks are finer in texture.
  • Igenous means made of fire, whereas volcanic is named after the Roman god of fire, Vulcan.
  • About 90 to 95% of the top 10 miles of the Earth’s crust is made from igneous rock.

Past Lessons

101 February 12, 2024 (North America)
No Past Lessons

Upcoming Lessons

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