![]() 21 For comparison, water has a viscosity of about 1 cP (0.001 Pas). Although magma near the top of HMM may be more vesiculated and less dense, and while the first magmas to erupt at Leilani estates were relatively high-viscosity (Roman et al., 2021), we assume. Felsic mineral crystallisations occur at higher temperatures and produce lower heat of crystallisation so felsic melts cool as they set where basalts, and even moreso ultramafic lavas, can actually, initially, increase in temperature as they crystallise. With such a high silica content, these magmas are extremely viscous, ranging from 10 8 cP (10 5 Pas) for hot rhyolite magma at 1,200 C (2,190 F) to 10 11 cP (10 8 Pas) for cool rhyolite magma at 800 C (1,470 F). Add the fact that felsic melts tend to be water saturated and lose a lot of heat when they dehydrate near the surface and so tend to be much colder when observed and they are very viscous indeed. Felsic melts being much lower in magnesium and iron and relatively higher in sodium, potassium, lithium, and calcium, as well as silicon, have very little olivine and are high in feldspar minerals which have a very different micro structure (they are composed of long chains of interlinked silica tetrahedra that share atoms similar to polymers but with much higher melting points) and are far less able to flow past and around each other.ĭue to these differences in chemistry a felsic melt at 1000ᵒC will be many times more viscous than a mafic melt at the same temperature. The minerals that are highest in iron and magnesium are the olivines they are also quite soft and slippery due to their microstructure (individual silica tetrahedra that stack together to form grains that don't share any internal atomic bonds) which means they flow more easily past each other in a melt at a given temperature. In contrast, a high viscosity tends to trap bubbles such that they can build up pressure as they grow within the magma. ![]() Water has the effect of depolymerizing (6). Select one: True False The following statement is an interpretation: 'Temperatures over the last 100 years have increased roughly 1 degree Celsius. Viscosity is just the ability to resist flow - essentially, it is the opposite of fluidity. Partial crystallisation products are the primary factor, iron and magnesium are many times more common in mafic melts than felsic ones. The higher the number of bonds, the higher the viscosity One way to change the viscosity of a magma is too add water. Volcanoes that form along subduction zones tend to have higher viscocity magmas and are more likely to erupt explosively.
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