EAR 110 1st Edition Lecture 11Outline of Previous Lecture:I. Temperature and Pressure inside earthII. How do rocks melt?III. How do igneous rocks form?IV. How does magma solidify?V. How does magma form along divergent plate boundaries?VI. How does magma form along convergent plate boundaries?Outline of Current Lecture:I. Types of volcanoesII. How do gases affect magma?III. Viscosity and eruptionsIV. Classification of igneous rocksV. Lava flowsVI. Flood basalts Chapter 6: VolcanoesI. Types of volcanoesa. Scoria Conei. Small, typically mafic lava (low silica, high Fe/Mg)ii. Successive layers of ash/lavaiii. Rock types: vesicular basalt, nonvesicular basalt, scoriab. Shield Volcanoi. Broad, giant, low angled (due to low viscosity magma)ii. Example: Hawaii, Icelandiii. Successive layers of lava flowsiv. Often caldera in center of ventv. Magma fed by fissuresvi. Eruption into water forms pillow basaltsc. Composite volcanoi. Dangerous – felsic compositionii. Steep slopes – due to high viscosity magmaiii. Composed largely of pyroclastic material (ash, glassy material, breccias, some crystals)d. Volcanic domei. Very viscous magma - bulges outwardii. Siliceous magmaII. How do gases affect mamga?a. Subduction zoneThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. Begin with mafic magma; then partial melting increases silica content (becomes intermediate) then more partial melting further increases silica content (becomes felsic magma)ii. Weight percent water increases with melting (up to 10% water at the end)b. Dissolved gas held in magma by pressurec. Under less pressure, gas forms bubbleIII. Viscosity and eruptionsa. Controls shape of volcanoesb. All liquid – lava flows – low viscosity – maficIV. Classification of igneous rocksa. Extrusive (volcanic rocks)i. Felsic = rhyoliteii. Intermediate = andesiteiii. Mafic = basaltiv. Ultramafic = komatiitev. Others – obsidian, pumice, tuffV. Lava Flowsa. Tubes – insulated tube of hot, flowing materialb. Aa - more solid materialc. Pahoehoe – low crystals, ropy structured magmaVI. Flood Basaltsa. Plume rises through mantle to base of lithosphereb. Plume partially meltsc. Plume spreads with additional meltingd. Examplei. Columbia river (western US), Siberia, Indiaii. Largest = MOR/ocean floore. Hazardsi. Lava fountains, ash, lava flows into developed areasii. Eruptions near ice or snow melt ice and cause mudslides or floodsiii. Gas