Types of volcanic eruptions eruptions are associated with volatile-rich dacitic to rhyolitic lavas, and occur most typically at stratovolcanoes. Eruptions can last anywhere from hours to days, with longer eruptions being associated with more felsic volcanoes. Although they are associated with felsic magma, Plinian eruptions can just as well occur at basaltic volcanoes, given that the magma chamber differentiates and has a structure rich in silicon dioxide. Plinian eruptions are similar to both Vulcanian and Strombolian eruptions, except that rather than creating discrete explosive events, Plinian eruptions form sustained eruptive columns. They are also similar to Hawaiian lava fountains in that both eruptive types
Lithology for the presence of calcite (or other forms of calcium carbonate) using dilute hydrochloric acid and looking for effervescence. The mineralogical composition of a rock is one of the major ways in which it is classified. In general, igneous rocks can be categorized by increasing silica content as ultramafic, mafic, intermediate, or felsic, though more mineral-specific classifications also exist. Likewise, metamorphic facies, which show the degree to which a rock has been exposed to heat and pressure and are therefore important in classifying metamorphic rocks, are determined by observing the mineral phases that are present in a sample. The colour