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9.2 Magma and Erupted Materials Purpose: After completing this lesson we learn what materials erupt from volcanoes.

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Presentation on theme: "9.2 Magma and Erupted Materials Purpose: After completing this lesson we learn what materials erupt from volcanoes."— Presentation transcript:

1 9.2 Magma and Erupted Materials Purpose: After completing this lesson we learn what materials erupt from volcanoes.

2 Types of Magma  Magma is molten rock. The main “ingredient” in rocks is a mineral named silica (SiO 2 ); 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 common  Silica, 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 Types of Magma  There are three types of magma, depending on the content of silica: 1. Basaltic 1. Basaltic 2. Andesitic 2. Andesitic 3. Rhyolitic 3. Rhyolitic

4 Basaltic Magma Some characteristics of basaltic magma are:  it has about 50% silica  has a small amount of gases dissolved  flows easily (least viscous)  the eruption is rarely explosive  it has the highest melting point (>1300 C degrees)

5 Basaltic Eruption  Lava flows easily, due to reduced viscosity

6 Andesitic Magma  contains about 60% silica  Has a moderate amount of gasses  Sometimes it generates explosive eruptions  The melting temperature is around 1000 C degrees

7 Andesitic Eruption  This is an explosive eruption

8 Rhyolithic Magma  Contains most silica ( over 70%)  Contains a significant amount of dissolved gasses  It 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 Eruption  This 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 spots  Andesitic magma is found at subduction boundaries  Rhyolitic magma is found at continental hot spots.

11 Magma versus Lava  Magma 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) -volcanic ashes (the particles have less than 2 mm in diameter) -lapilli- pebbles with diameters between 2-64 mm -lapilli- pebbles with diameters between 2-64 mm - bombs or blocks, are fragments larger than 64 mm - bombs or blocks, are fragments larger than 64 mm

13 Types of Lava Flow  Pahoehoe is lava with smooth, ropelike surfaces.

14 Pillow Lava  Lava that cools under water has a rounded, pillow like form.

15 Aa  Aa is lava that cools quickly with a rough, jagged surface.


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