Changes

*Volcanic rock (or lava) that characteristically is light in color, contains 69 percent silica or more, and is rich in potassium and sodium. (Foxworthy and Hill, 1982)  

Volcanic rock (or lava) that characteristically is light in color, contains 69 percent [[silica]] or more, and is rich in [[potassium]] and [[sodium]]. <ref>[http://vulcan.wr.usgs.gov/Glossary/volcano_terminology.html Glossary of Volcano and Related Terminology (Foxworthy and Hill, 1982) ]</ref>

*'''Rhyolite''' is a light-colored rock with silica (SiO2) content greater than about 68 weight percent. Sodium and potassium oxides both can reach about 5 weight percent. Common mineral types include quartz, feldspar and biotite and are often found in a glassy matrix. Rhyolite is erupted at temperatures of 700 to 850° C. (USGS/VHP) <ref>[http://vulcan.wr.usgs.gov/Glossary/volcano_terminology.html Glossary of Volcano and Related Terminology]</ref>

 

'''Rhyolite''' is a light-colored rock with [[silica]] (SiO2) content greater than about 68 weight percent. [[Sodium]] and [[potassium]] [[oxides]] both can reach about 5 weight percent. Common mineral types include [[quartz]], [[feldspar]] and [[biotite]] and are often found in a glassy [[matrix]]. Rhyolite is erupted at temperatures of 700 to 850° C. <ref>[http://vulcan.wr.usgs.gov/Glossary/volcano_terminology.html Glossary of Volcano and Related Terminology (USGS/VHP)]</ref>

==References==

==References==

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