Magmatic Volatiles - John Seach
Magmatic volatiles are the gas species which are present in magma and form bubbles at low pressure. Water and carbon dioxide are the most important volatiles in magma. Other volatiles include sulfur, chlorine and fluorine. Most volatiles are lost once the magma reaches the low pressure of the earth's atmosphere. There may be small amounts of volatiles trapped in scoria glass or pumice. Submarine erupted magmas are cooled under pressures of 500-600 atm and may be trapped under a rapidly cooled skin.