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
Lava delta Lava delta Lava deltas, similar to river deltas form wherever sufficient sub-aerial flows of lava enter standing bodies of water. The lava cools and breaks up as it encounters the water, with the resulting fragments filling in the adjacent seabed topography such that the flow can move further offshore sub-aerially. Lava deltas are generally associated with large-scale, effusive type basaltic volcanism. Lava deltas are found mainly associated with volcanic islands, particularly those formed at hotspots as they produce the necessary effusive basaltic flows. The largest lava delta systems known are associated with formation of volcanic type passive margins. Just prior