Volcanic rock
Videos
Volcanic rocks are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic ro
Ignimbrite, a volcanic rock deposited by pyroclastic flows
Photomicrograph of a volcanic lithic fragment (sand grain); upper picture is plane-polarized light, bottom picture is cross-polarized light, scale box at left-center is 0.25 millimeter.
An aphanitic volcanic sand grain, with fine-grained groundmass, as seen under a petrographic microscope
Vesicular olivine basalt from La Palma (green phenocrysts are olivine).
Extrusive rock
Videos
Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out onto the surface as lava or explodes violently into the atmosphere to fall back
A volcanic rock from Italy with a relatively large six-sided phenocryst (diameter about 1 mm) surrounded by a fine-grained groundmass, as seen in thin section under a petrographic microscope