extrusive rock

crystal size

Crystals in aphantic rocks are small in size due to their rapid formation during eruption.

effect of extrusion

The main effect of extrusion is that the magma can cool much more quickly in the open air or under seawater, and there is little time for the growth of crystals.

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intrusive rock

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Waiting for Godot (YouTube)

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Igneous rocks can be either intrusive (plutonic and hypabyssal) or extrusive (volcanic).

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texture

The texture of extrusive rocks is characterized by fine-grained crystals indistinguishable to the human eye, described as aphantic.

Wikidata

https://www.wikidata.org/wiki/Q1352521

Wikipedia

Extrusive rock (Wikipedia) Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. In contrast, intrusive rock refers to rocks formed by magma which cools below the surface.