This presentation provides an overview of volcanoes, including their formation from plate tectonics or hotspots, the different types of volcanic features and erupted materials, classifications of volcanic activity, and notable examples. Volcanic activity can have effects on global climate through emissions into the stratosphere and impacts soil through added nutrients.

1. PRESENTATION ON VOLCANOS BY ANJALI PATRA ANKITA TRIPATHY

3. Contents 1 Introduction 2 Plate tectonics and hotspots 3 Volcanic features 4 Erupted material 5 Volcanic activity 6 Notable volcanoes 7 Effects of volcanoes 8 Volcanoes on other planetary bodies 9 Panoramas

4. INTRODUCTION A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, ash and gases to escape from below the surface. The word volcano is derived from the name of Vulcano island off Sicily which in turn, was named after Vulcan, the Roman god of fire. Volcanoes are generally found where tectonic plates are diverging or converging. Volcanoes can also form where there is stretching and thinning of the Earth's crust (called "non-hotspot intraplate volcanism"). Volcanoes can be caused by mantle plumes. The study of volcanoes is called volcanology, sometimes spelled vulcanology.

5. Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station, May 2006

9. Other types of volcano include

10. Cryovolcanoes - ice volcanoes

11. Fissure vents - Flat, linear cracks through which lava emerges.

13. Cryptodomes -viscous lava forces its way up and causes a bulge, under great pressure.

14. Volcanic cones (cinder cones) -erupt mostly small pieces of scoria and pyroclastics.

15. Stratovolcanoes (composite volcanoes) -made of cinders, ash and lava.

17. Subglacialvolcanoes-develop underneath icecaps, flat lava which flows at the top of extensive pillow lavas and palagonite.

19. Erupted material Lava composition Another way of classifying volcanoes is by the composition of material erupted (lava), since this affects the shape of the volcano. Lava can be broadly classified into 4 different compositions :- If the erupted magma contains a high percentage (>63%) of silica, the lava is called felsic. If the erupted magma contains 52–63% silica, the lava is of intermediate composition. If the erupted magma contains <52% and >45% silica, the lava is called mafic or basaltic. Some erupted magmas contain <=45% silica and produce ultramafic lava.

20. Lava texture Two types of lava are named according to the surface texture: ʻAʻa (pronounced [ˈʔaʔa]) and pāhoehoe ([paːˈho.eˈho.e]).ʻAʻais characterized by a rough, clinkery surface and is the typical texture of viscous lava flow.Pāhoehoeis characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows.

22. Potentially Active - Solfataras / Fumaroles - Geologically young (possibly erupted < 10,000 years and for calderas and large systems - possibly < 25,000 years). - Young-looking geomorphology (thin soil cover/sparse vegetation; low degree of erosion and dissection.

24. Mount Etna, Sicily, Italy

25. Mauna Loa, Hawaii, USA

26. Mount Rainier, Washington, USA

27. Vesuvius, Naples, Italy

29. Acid rain

30. a decline in the average temperature

31. complex chemical reactions on Earth’s surface

32. visual effects such as unusually colorful sunsets and affect global climate mainly by cooling it.

33. benefit of adding nutrients to soil.

34. create new islands Volcanoes on other planetary bodies The Earth's Moon has no large volcanoes and no current volcanic activity. he planet Venus has a surface that is 90% basalt, indicating that volcanism played a major role in shaping its surface. There are several extinct volcanoes on Mars, four of which are vast shield volcanoes far bigger than any on Earth. Jupiter's moon Io is the most volcanically active object in the solar system

35. Panoramas Mount Bromo, East Java, Indonesia.

36. Irazú Volcano, Costa Rica.

37. Vulcano island with the north coast of Sicily in the background.

38. Pinatubo ash plume

39. Fourpeaked volcano, Alaska, in September 2007, after being thought extinct for over 10,000 years.

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