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Geology & Earth Sciences vocabulary · Rocks & Minerals

Igneous rock

Meaning in geology & earth sciences, with examples

/ˈɪɡniəs rɑːk/nounCore term

In geology & earth sciences, igneous rock means: Rock that forms when molten magma or lava cools and becomes solid. Granite forms slowly underground, while basalt forms quickly at the surface.

In Turkish: magmatik kayaç, püskürük kayaç

How it is used

One of the three main rock groups. Textbooks divide igneous rocks into intrusive (plutonic) rocks, which cool inside the crust, and extrusive (volcanic) rocks, which cool at the surface. Grain size usually tells you which is which.

Example sentences

  1. The large crystals tell us that this igneous rock cooled slowly at depth.

  2. Most of the oceanic crust is made of igneous rocks such as basalt and gabbro.

Common collocations

  • intrusive igneous rock
  • extrusive igneous rock
  • igneous intrusion
  • igneous activity
  • magmaMolten or partly molten rock beneath the Earth's surface, often containing crystals and dissolved gases. It is called lava once it reaches the surface.
  • lavaMolten rock that has come out of a volcano onto the Earth's surface, and also the solid rock that forms when it cools.
  • graniteA light-coloured, coarse-grained igneous rock made mainly of quartz, feldspar and mica, formed when magma cools slowly deep in the crust.
  • basaltA dark, fine-grained igneous rock formed when lava cools quickly at or near the surface. It is the most common volcanic rock and makes up the ocean floor.
  • rock cycleThe model that shows how igneous, sedimentary and metamorphic rocks change into one another over long periods through melting, weathering, burial and heat.

More terms: Rocks & Minerals

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