Meaning & use
igneous rock
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Meaning
nouncountable or uncountabletechnical
Rock that forms when hot melted material from inside the Earth cools and becomes solid.
Grammar: Can be countable when talking about types: an igneous rock, granites and other igneous rocks; uncountable when talking about the material in general: The cliff is made of igneous rock.
Patterns
- igneous rock forms
- a type of igneous rock
- made of igneous rock
Granite is a common igneous rock that cooled slowly deep underground.
The island is mostly igneous rock produced by ancient volcanoes.
Geologists classify igneous rocks by how quickly the melted material cooled.
Word forms
| plural | igneous rocks |
|---|
Common combinations
- igneous rock formation
- The hike passes a striking igneous rock formation.
- intrusive igneous rock
- Intrusive igneous rock cools below the surface and has large crystals.
- extrusive igneous rock
- Extrusive igneous rock cools quickly at the surface after a volcanic eruption.
- igneous rock is formed
- Igneous rock is formed when magma or lava solidifies.
- a layer of igneous rock
- Drilling revealed a thick layer of igneous rock beneath the soil.
Synonyms and how they differ
- volcanic rock
- Use volcanic rock mainly for igneous rock that cooled at the surface; igneous rock also covers rock that cooled deep underground.
- magmatic rock
- A more technical term used in some geology texts; igneous rock is the usual term in school and general writing.
Word family
- igneous adjective
- Relating to rock formed from cooled magma or lava.
Commonly confused: igneous rock or sedimentary rock? igneous rock or metamorphic rock?
igneous rock vs sedimentary rock
Sedimentary rock forms from layers of sand, mud, or shells, not from cooling melted material.
igneous rock vs metamorphic rock
Metamorphic rock forms when existing rock is changed by heat and pressure, not by cooling from a melt.
Practice
Which sentence uses "igneous rock" correctly?
Choose one answer.
Basalt really is an igneous rock formed by cooling lava, so option 3 fits. Option 1 describes limestone, which is sedimentary; option 2 describes layering, typical of sedimentary rock; option 4 describes metamorphic change, not igneous formation.
Make it your own
Write a sentence using “igneous rock”, then check it and compare it with the examples above.