extrusive
Volcanic rock type
Extrusive describes rock formed when molten material erupts onto Earth's surface and cools quickly.
Basalt and obsidian are extrusive rocks, formed from lava rather than from magma cooling slowly underground.
The term contrasts with intrusive, which describes rock that solidifies beneath the surface: The Hawaiian islands are built from extrusive volcanic rock.
Erupted liquid stone
- eruptionViolent sudden release
- pyroclasticHot eruption debris
- ashCombustion's powdery remains
- tephraEjected volcanic material
vent · caldera · stratovolcano · fumarole · spatter · volcanologist · geyser · hotspot
Fine-grained volcanic stone
Composed of minute particles
- glassySmooth and shiny
- vesicularHaving small sacs
- porousAllowing passage of fluids
- groundmassRock's fine-grained foundation
ropy · blocky · pillow · microcrystalline
lava
Erupted liquid stone
- eruptionViolent sudden release
- pyroclasticHot eruption debris
- ashCombustion's powdery remains
tephra · vent · caldera · stratovolcano · fumarole · spatter · volcanologist · geyser · hotspot · fissure
basalt
Fine-grained volcanic stone
pumice · scoria · tuff · perlite · pitchstone · glassy · vesicular
fine-grained
Composed of minute particles
groundmass · ropy · blocky · pillow · microcrystalline
intermediate
Between two levels
magma · olivine · pyroxene · quartz · feldspar · amphibole · temperature · fluidity
aa
Sharp, blocky lava flow
extrusiveintrusive
Invading others' privacy
plutonic · deep-seated · subsurface · subterranean · abyssal