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Volcanoes and Their Products
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Magma may contain up to 7% volatiles (dissolved gases). Water vapor is the most common volatile, carbon dioxide too may be significant, and lesser amounts of other gases are typically present. In particular, besides water and carbon dioxide, magmas typically contain sulfur, either in the form of sulfur dioxide or as hydrogen sulfide. The amount of sulfur varies from volcano to volcano. When a magma reaches Earth’s surface, gas pressure is released and the dissolved gases may escape into the atmosphere. Commonly, however, some gas bubbles become trapped, forming open holes called vesicles, which are preserved in solidified vesicular volcanic rock. Figure 7.27 shows a colorful lizard on top of vesicular basalt on Lanzarote Island in the Canary Islands, Spain.
Magmatism and Magmatic Rocks
Published in Aurèle Parriaux, Geology, 2018
When lava contains lots of gas, the rock texture is called vesicular (scoria, pumice). The variety called liparite (from the island of Lipari in northern Sicily) has abundant vesicles that are not interconnected, which allows them to float. Pozzolans are scoriaceous volcanic ashes rich in silica, aluminum and iron oxide.
Magmatism and Magmatic Rocks
Published in Aurèle Parriaux, Geology, 2018
When lava contains lots of gas, the rock texture is called vesicular (scoria, pumice). The variety called liparite (from the island of Lipari in northern Sicily) has abundant vesicles that are not interconnected, which allows them to float. Pozzolans are scoriaceous volcanic ashes rich in silica, aluminum and iron oxide.
Spectral indices derived, non-parametric Decision Tree Classification approach to lithological mapping in the Lake Magadi area, Kenya
Published in International Journal of Digital Earth, 2018
Gayantha R. L. Kodikara, Tsehaie Woldai
Trachyte series rocks collected from the study area were grouped based on their texture and petrology. Basaltic rocks (e.g. P020) containing pyroxene and plagioclase phenocrysts.Alkali trachytes (e.g. P033, Figure 3) characterized by fine-grain matrix in greenish or brownish color.Rhyolite (e.g. P005, Figure 3). Volcanic rock, mainly composed of alkali feldspar and free silica with a minor amount of mafic minerals. The rocks are characterized by light brown color with an aphanitic texture.Scoriaceous basalt (e.g. P015, Figure 3). Basaltic rocks with empty cavities. It is heavier, darker and more crystalline than pumice.Vesicular basalt (e.g. P001) is a basaltic rock with small ellipsoidal cavities which are formed by bubbles of gas trapped during the solidification of rocks.