For Igneous rocks we have terms and definitions in 3 topics. The topics are Natural Hazards, Science and Volcano.

Igneous Rocks (Natural Hazards)

Igneous rocks make up most of the earth's surface, and can form in two ways:

* from (mainly) silicate magma forced from a volcano or a volcanic vent (‘extrusive’)
* within the earth’s crust as a molten body (‘intrusive’), which becomes visible on the surface when the overlying sediment and soil has been eroded away.

Igneous Rocks (Science)

Rock produced by the freezing of molten rock.

Igneous Rocks (Volcano)

Igneous rocks are formed from melted rock that has cooled and solidified. When rocks are buried deep within the Earth, they melt because of the high pressure and temperature; the molten rock (called magma) can then flow upward or even be erupted from a volcano onto the Earth's surface. When magma cools slowly, usually at depths of thousands of feet, crystals grow from the molten liquid, and a coarse-grained rock forms. When magma cools rapidly, usually at or near the Earth's surface, the crystals are extremely small, and a fine-grained rock results. A wide variety of rocks are formed by different cooling rates and different chemical compositions of the original magma. Obsidian (volcanic glass), granite, basalt, and andesite porphyry are four of the many types of igneous rock. (Barker, 1997)

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