Lava Vesuvius between May 14 and June 4, 1737. Serao described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of the volcano following heavy rain. The composition of almost all lava of the Earth's crust is dominated by silicate minerals, mostly feldspars, olivine, pyroxenes, amphiboles, micas and quartz. Igneous rocks, which form lava flows when erupted, can be classified into three chemical types: "felsic", "intermediate", and "mafic" (four if one includes the super-heated "ultramafic"). These classes are primarily chemical, however, the chemistry of lava also tends to correlate with the magma
Geology of Wisconsin and metavolcanics formed first, followed by granites more than 2.7 billion years ago. The rock record contains an uncertain age gap with younger 2.3 billion year old Proterozoic quartzofeldspathic and migmatite gneiss, with amphibolite and biotite schist. Around 1.9 billion years ago, mafic, intermediate and felsic rocks, in some cases with subordinate metasedimentary rocks, began to form and metamorphosed, reaching greenschist and amphibolite grade on the sequence of metamorphic facies. The Ironwood and Riverton Iron formations are recognized from aerial magnetic surveys. Metamorphosed argillite, quartzite, greywacke conglomerate and marble with small areas of interbedded metavolcaic rocks make up the Tyler