Final answer:
The classification of lava is based on the mineral composition and texture, which refers to crystal size determined by the cooling rate. Slow cooling results in coarse-grained intrusive rocks such as granite, while rapid cooling leads to fine-grained extrusive rocks like basalt. Rock naming varies according to specific mineral amounts and grain sizes, exemplified by diorite and andesite.
Step-by-step explanation:
Classification of Lava
The classification of lava is primarily based on composition and texture. These factors are influenced by the original chemical makeup of the magma and the cooling process it undergoes. When it comes to igneous rocks, which form from the solidification of magma or lava, the size of the mineral grains within the rock is pivotal, determined by the rate at which the magma cools. Slowly cooling magma, which stays beneath the Earth's surface, forms intrusive or plutonic rocks with larger crystals, such as granite. Conversely, when lava is ejected onto the surface and cools rapidly, smaller mineral grains form, leading to extrusive or volcanic rocks like basalt or rhyolite.
The actual naming of an igneous rock is based on the amount of specific minerals it contains. For instance, a rock with a composition of 10% quartz, 50% plagioclase feldspar, 10% potassium feldspar, 20% pyroxene, and 10% amphibole with coarse grains would be classified as diorite. On the other hand, if these minerals are of fine grain size, the rock would then be identified as andesite.
Volcanic fragmental rocks, like tuff and agglomerate, are also classified based on the size and origin of their particles. Agglomerate is made up of large volcanic fragments, typically greater than 2 centimeters. These classifications are key to understanding both geological and archeological histories, as the dating of volcanic materials can provide insight into when certain objects were created or used, primarily through radiometric dating techniques which focus on the consistent chemical signatures of materials from a volcanic eruption.