Igneous rock (derived from the Latin word ignis meaning fire) is one of the three main rock types, the others being sedimentary and metamorphic rock. Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of Earth's crust.
Read more about Igneous Rock: Geological Significance, Morphology and Setting, Classification, Mineralogical Classification, Magma Origination, Etymology
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“When we were at school we were taught to sing the songs of the Europeans. How many of us were taught the songs of the Wanyamwezi or of the Wahehe? Many of us have learnt to dance the rumba, or the cha cha, to rock and roll and to twist and even to dance the waltz and foxtrot. But how many of us can dance, or have even heard of the gombe sugu, the mangala, nyang’umumi, kiduo, or lele mama?”
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