magma-and-other-volcanic-materials.pptxreal

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1. MAGMA and other Volcanic Materials

2. Let’s Review… Compare and contrast magma and lava. What plate boundaries will result in formation of a volcano?

3. Magma has a wide range of compositions, but silica (SiO 2 ) always dominates the mix. has high temperatures. fluid—it has the ability to flow. Most magma actually is a mixture of liquid (often referred to as melt) and solid mineral grains.

4. Composition of Magmas and Lavas The composition of magmas and lavas is controlled by the most abundant elements in the Earth—Si, Al, Fe, Ca, Mg, Na, K, H, and O. chemical composition (largely silica dioxide - SiO 2 ) and gas content (largely water vapor and CO 2 ). SiO 2 content controls the viscosity of a magma

5. Viscosity of Magmas and Lavas The internal property of a substance that offers resistance to flow is called viscosity. The more viscous a magma, the less easily it flows. Viscosity of a magma depends on temperature and composition (especially the silica and dissolved-gas contents).

6. Types of Magma Basaltic, containing about 50 percent SiO 2. Andesitic, about 60 percent SiO 2. Rhyolitic, about 70 percent SiO 2.

7. Magma Type Chemical Composition Temperature (degrees C) Viscosity Gas Content Basaltic 45-55% SiO 2 ; High in Fe, Mg, Ca; Low in K, Na. 1000 - 1200 Low Low Andesitic 55-65% SiO 2 ; Intermediate Fe, Mg, Ca, Na, K 800-1000 Intermediate Intermediate Rhyolitic 65-75% SiO 2 ; Low in Fe, Mg, Ca; High in K, Na 650-800 High High

8. Types of volcanic deposits (photos from USGS) Volcanoes also vary in terms of the types of deposits that they produce. Lava : Hot (up to 1200 degrees C), fluid, molten rock that flows along the land surface.

9. Lava can flow like viscous water, including forming lava falls.

10. Pahoehoe : Lava with a ropelike surface texture due to partial cooling as the lava flowed. Relatively hot, low viscosity lava.

11. Pahoehoe

12. A thick deposit of pahoehoe lava

13. Aa : Blocky, rough lava flow. Due to high viscosity lava that flowed pushing chunks of solid and semi-solid blocks. www.volcanovideo.com/Movies/p8vdclp.htm

14. Lava tube : A tube formed by cooling and solidifying of the lava walls while fluid lava continued to flow inside.

15. Pillows : A form of closed lava tube (with a bulbous end) that forms when a lava flows into water (e.g., a lake or ocean) and cools very rapidly.

16. Pyroclastic material : Debris formed by a volcanic explosion. Results when magma is very viscous. Rapidly moving volcanic material. Speeds up to 200km/h May contain hot, poisonous gases Tephra : The general term for all pyroclastic material that is ejected from a volcano. Different terms apply according to the size of the tephra.

17. Tephra Pyroclastic Flow

18. Ash : tephra that is finer than 2 mm in diameter.

19. Lapilli : from 2 mm to 64 mm in diameter. Blocks : hard fragments greater than 64 mm in diameter.

20. Bombs : soft, partially melted fragments greater than 64 mm in diameter.

21. Tuff : A deposit made up of ash. Welded tuff : A deposit of pyroclastic material that was laid down while still very hot and particles become fused together. Ash fall : Fallout of very fine ash from the air. Volcanic ash fall during mid-day with the eruption of Mount Pinatubo in the Philippines.

22. Ash flow : Pyroclastic debris that flows downslope. Lahar : A water saturated slurry of ash and other volcanic debris that flows downslope.

23. Nuée Ardente (glowing cloud) : A hot, gaseous cloud of ash that flows down slope. http://volcano.und.nodak.edu/vwdocs/volc_images/img_mt_pelee.html Flow speeds can reach 160 km/hr and temperatures can exceed 600 degrees C.

24. How Volcanoes Erupt?

25. What are the signs of an impending Volcanic Eruption?

26. What is Geothermal Energy?

27. What are the types of Geothermal power plant?