Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks.
For these reasons, in geology, volcanics and shallow hypabyssal rocks are not always treated as distinct.
Pyroclastic rocks are the product of explosive volcanism. Pyroclastic rocks are often the result of volcanic debris, such as ash, bombs and tephra, and other volcanic ejecta.
Examples of pyroclastic rocks are tuff and ignimbrite.
Volcanic rocks are usually fine-grained or aphanitic to glass in texture.
They often contain clasts of other rocks and phenocrysts.
Volcanic rocks are named according to both their chemical composition and texture.
Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from magma erupted from a volcano.
In other words, it differs from other igneous rock by being of volcanic origin.
Dorn -- Thermoluminescence dating of surficial archaeological material / Robert C. Feathers -- Surface exposure dating with cosmogenic nuclides / Mark D. Brook -- Surface exposure dating by cosmogenic chorine-36 accumulation / Marek G. Phillips -- Lichenometric dating: a review with particular reference to 'Little Ice Age' moraines in southern Norway / John A.
Matthews -- Using dendrochronology for the dating of land surfaces / Olavi Heikkinen.