Gases Dissolved in Magma Small amounts of gas(0.2 to 3%o by weight)are dissolved in all magma The principal gas in water vapor, which together with carbon dioxide, accounts for more than 98 percent of all gases emitted from volcanoes
Gases Dissolved in Magma ◼ Small amounts of gas (0.2 to 3% by weight) are dissolved in all magma. ◼ The principal gas in water vapor, which, together with carbon dioxide, accounts for more than 98 percent of all gases emitted from volcanoes
Temperature of Magmas and Lavas Magma temperatures range from 10000 to 12000C Magma temperatures can reach 1400C under some conditions
Temperature of Magmas and Lavas ◼ Magma temperatures range from 1000o to 1200oC. ◼ Magma temperatures can reach 1400oC under some conditions
Viscosity of Magmas and Lavas (1) The internal property of a substance that offers resistance to flow is called viscosity. The more viscous a magma, the less easily it flows Viscosity of a magma depends on temperature and composition(especially the silica and dissolved-gas contents)
Viscosity of Magmas and Lavas (1) ◼ The internal property of a substance that offers resistance to flow is called viscosity. ◼ The more viscous a magma, the less easily it flows. ◼ Viscosity of a magma depends on temperature and composition (especially the silica and dissolved-gas contents)
Viscosity of Magmas and Lavas(2) The higher the temperature, the lower the viscosity, and the more readily magma flows The smooth, ropy-surfaced lava in Hawaii, formed from a very hot, very fluid lava is called pahoehoe绳状熔岩 The rough-looking lava formed from a cooler lava having a high viscosity is called aa (ahah)
Viscosity of Magmas and Lavas (2) ◼ The higher the temperature, the lower the viscosity, and the more readily magma flows. ◼ The smooth, ropy-surfaced lava in Hawaii, formed from a very hot, very fluid lava is called pahoehoe 绳状熔岩. ◼ The rough-looking lava formed from a cooler lava having a high viscosity is called aa (ah ah)
Viscosity of Magmas and Lavas 3) The greater the silica content, the larger is the viscosity. a For this reason, rhyolitic magma(70% silica) is always more viscous than basaltic magma(50%silica) Andesitic magma has a viscosity that is intermediate between the two(60% slca
Viscosity of Magmas and Lavas (3) ◼ The greater the silica content, the larger is the viscosity. ◼ For this reason, rhyolitic magma (70% silica) is always more viscous than basaltic magma (50% silica). ◼ Andesitic magma has a viscosity that is intermediate between the two (60% silica)