GG231 Chapter 4: Chapter 4.docx
Document Summary
Mount unzen, 1991: one of the most destructive of japan"s 19 volcanoes, more than 200 years ago killed an estimated 15,000 people, lay dormant until june 3, 1991 when another eruption forced the evacuation of. 12,000 people: produced 0. 2 km of lava and more than 10,000 superheated flows of hot gas, ash and large rock fragments, more flows than any other volcano in recent time. Magma: composed of melted silicate minerals and dissolved gases, main elements include: oxygen, silicon, aluminum, iron, magnesium, calcium, sodium and potassium. Gentle sloped sides and broad summits: among the tallest mountains on earth when measured from their bases, common on the hawaiian islands, iceland and some islands in the indian. Ocean: non-explosive eruptions of very hot, low-viscosity, basaltic magmas, magma of basaltic composition erupts as lava through openings, or vents, in the volcano and flows down its sides.
