Presentation on theme: "9.2 Magma and Erupted Materials"— Presentation transcript:
1 9.2 Magma and Erupted Materials Purpose: After completing this lesson we learn what materials erupt from volcanoes.
2 Types of MagmaMagma is molten rock. The main “ingredient” in rocks is a mineral named silica (SiO2); besides silica, there are many other minerals.Magma also contains significant amounts of fluids dissolved in the molten rock: water vapors and carbon dioxide are most commonSilica, however, is the one that determines the type of magma in every igneous activity.Silica determines the viscosity (resistance to flow) of magma as well.
3 There are three types of magma, depending on the content of silica: 1. Basaltic2. Andesitic3. Rhyolitic
4 Basaltic Magma Some characteristics of basaltic magma are: it has about 50% silicahas a small amount of gases dissolvedflows easily (least viscous)the eruption is rarely explosiveit has the highest melting point (>1300 C degrees)
5 Basaltic EruptionLava flows easily, due to reduced viscosity
6 Andesitic Magma contains about 60% silica Has a moderate amount of gassesSometimes it generates explosive eruptionsThe melting temperature is around 1000 C degrees
8 Rhyolithic Magma Contains most silica ( over 70%) Contains a significant amount of dissolved gassesIt has a high viscosity (flows very slowly)The eruptions are usually explosive and create tremendous damage.The melting point is below 900C degrees.
9 Rhyolithic EruptionThis type is highly explosive
10 Location of Each Type of Magma Each type pf magma form in certain areas:Basaltic magma is found at rifts and hot spotsAndesitic magma is found at subduction boundariesRhyolitic magma is found at continental hot spots.
11 Magma versus LavaMagma is the molten material that rises from the deep. It contains a significant amount of volatile compounds; water vapors and CO2 are most common. As the magma reaches the surface of the earth, it loses very quickly the volatiles, because of the difference in pressure. (Shake a can of soda and open it quickly; the fizz is nothing else but the CO2 which is released from the liquid)Lava is magma which has lost most of its volatile components. Lava has temperatures between 700 and 1200 C degrees.
12 Other Volcanic Products Lava is the main product that is released from a volcano.Pyroclastic materials (“pyro” means hot and “clast” means fragment in Greek). These are hot, solid materials of different sizes. Sometimes the lava cools down on the pipe, creating a plug; the magma is climbing up the pipe at great pressures, and breaks apart this plug, creating fragments of different sizes.The most common pyroclastic materials are:-volcanic ashes (the particles have less than 2 mm in diameter)-lapilli- pebbles with diameters between 2-64 mm- bombs or blocks, are fragments larger than 64 mm
13 Types of Lava FlowPahoehoe is lava with smooth, ropelike surfaces.
14 Pillow LavaLava that cools under water has a rounded, pillow like form.
15 AaAa is lava that cools quickly with a rough, jagged surface.