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Felsic. In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz. [1] It is contrasted with mafic rocks, which are relatively richer in magnesium and iron. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen ...
Eruptions can last anywhere from hours to days, with longer eruptions being associated with more felsic volcanoes. Although they are usually associated with felsic magma, Plinian eruptions can occur at basaltic volcanoes, if the magma chamber differentiates with upper portions rich in silicon dioxide, [40] or if magma ascends rapidly. [42]
The most famous and destructive historical eruptions are mainly of this type. An eruptive phase can consist of a single eruption, or a sequence of several eruptions spread over several days, weeks or months. Explosive eruptions usually involve thick, highly viscous, silicic or felsic magma, high in volatiles like water vapor and carbon dioxide.
The word lava comes from Italian and is probably derived from the Latin word labes, which means a fall or slide. [2] [3] An early use of the word in connection with extrusion of magma from below the surface is found in a short account of the 1737 eruption of Vesuvius, written by Francesco Serao, who described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of ...
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. The process that forms volcanoes is called volcanism. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and because most of Earth ...
From the 1631 eruption until 1944, there was a comparatively small eruption every few years, emitting 0.001–0.01 km 3 of magma. For Vesuvius, the amount of magma expelled in an eruption increases roughly linearly with the interval since the previous one, and at a rate of around 0.001 cubic kilometres (0.00024 cu mi) for each year. [75]
Archean felsic volcanic rocks are felsic volcanic rocks that were formed in the Archean Eon (4 to 2.5 billion years ago). [2] The term "felsic" means that the rocks have silica content of 62–78%. [3] Given that the Earth formed at ~4.5 billion year ago, [4] Archean felsic volcanic rocks provide clues on the Earth's first volcanic activities ...
The magma forming this lava is often felsic, having high to intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less viscous mafic magma. [2] Extensive felsic lava flows are uncommon, but have traveled as far as 15 km (9 mi). [3] Stratovolcanoes are sometimes called composite volcanoes because of their ...