Volcanoes are formed when one tectonic plate moves over another. A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and most are found underwater.
1. Section 3.2-3.3 HOLY SMOKES-IT’S A VOLCANO! • http://video.nationalgeographic.com/video/kids/forces-of-nature-kids/volcanoes-101-kids/
2. What is a volcano? • Volcano: an opening in Earth’s crust through which molten rock, rock fragments, and hot gases erupt. – Magma vs. lava: remember the difference?
3. DIAGRAM THIS-pg. 87 has a similar but untitled diagram
4. Where do volcanoes occur? Most form along plate boundaries …. 1. in subduction zones (one plate sinks under another) 2. over hot spots 3. where plates are pulling apart
5. See page 89
6. What determines how explosive an eruption 1. Water Vapor: Vapor more water=bigger explosion 2. Trapped gases (water and CO2): – Easy escape (low pressure)=quiet eruption – Difficult to escape (high pressure)=explosive/violent eruption 3. Magma Type: – Balastic (thin) =quiet eruption – Granitic/Andestic (thick)=violent eruption **NOTE: A Pyroclastic flow is a fast moving mixture of water, gases and ash that can be deadly
7. Magma Composition Basaltic the same (pa-HOY-hoy) •If pahoehoe As lava flows at a rocktemperature, lower structures shaped a stiff, lava cools, it like tubes, slowly forms movingballoons,a or lava aa (AH-ah) • Volcanoes with basaltic underwater pillows.structure ropelike . pillow lava produce: lava formations
8. Magma Composition Basaltic Examples • You can find volcanoes with basaltic lava – Hawaiian Volcanoes, including • Kilauea • Mona Loa – Iceland • Heimaey • Hekla
9. Magma Composition Granitic Lava “If it had erupted in a populated area…"The magnitude of the • Some examples of granitic eruption can perhaps be best realized if one could imagine a volcanoes are similar outburst centered in New – Yellowstone Caldera York City. All of Greater New York • It is a super voclano! would be buried under from ten to fifteen feet of ash; Philadelphia – Katmai, Alaska would be covered by a foot of gray • Last eruted in 1912. ash and would be in total darkness for sixty hours; Washington and Buffalo would receive a quarter of an inch of ash, with a shorter period of darkness. The sound of the explosion would be heard in Atlanta and St. Louis, and the fumes noticed as far away as Denver, San Antonio, and Jamaica."
10. Magma Composition Andesitic Lava Mount Pelee, Martinique – Famous for the May 8, 1902 eruption which killed 29,000 people and destroyed the city of St. Pierre. This is the largest number of causalities for a volcanic eruption this century. • Mayon, Phillipines – It is the most active volcano in the Philippines. Since 1616, Mayon has erupted 47 times. – It’s 1814 eruption killed 1,600.
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12. 3 Basic Volcano shapes The shape and size are determined by the type of magma feeding it. Pg. 90-91
13. 1. Shield Volcano • Formed by quiet eruptions • Slow-moving lava flows • Basaltic lava builds up in flat layers • Largest with gently sloping sides • Ex: Mauna Kea-Hawaiian Islands
14. Example of Shield Volcano • Mauna Loa • Mt. Kilauea – Probably one of the world’s most active volcanoes. – The eruption of Kilauea Volcano that began in 1983 continues at the cinder-and-spatter cone of Pu`u `O`o Mt. Kilauea Picture from http://www.britannica.com/eb/art-89176/Hawai is-Kilauea-is-an-active-volcano
15. 2. Cinder Cone Volcano • Caused by explosive eruptions • Granitic lava thrown high into the air • Lava cools into different sizes of volcanic material called tephra • Steep-sided, loose slopes
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17. Example Cinder Cone Volcano • Parícutin Volcano in Mexico is a great example of a cinder cone volcano.
18. Paracútin • On February 20, 1943, a Mexican farmer noticed that a hole in his cornfield that had been there for as long as he could remember was giving off smoke. • Throughout the night, hot glowing cinders were thrown high into the air. • In just a few days, a cinder cone several hundred meters high covered his cornfield.
19. 3. Composite Volcano • A mix of the other two types • Quiet or violent • Basaltic or granitic • Steep or gentle slopes • Layered of tephra
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21. Example of Composite Volcano • Mount St. Helen’s – Erupted in 1980 – 57 fatalities – Over 7000 big game animals perished – 4 billion board feet of timber (enough to build about 300,000 two-bedroom homes) destroyed – Destroyed 27 bridges, nearly 200 homes. Blast and lahars destroyed more than 185 miles of highways and roads and 15 miles of railways.
22. Example of Composite Volcano • Mount Pinatubo – Erupted in 1991 – Killed 847 people – 184 people injured – 10, 000 home destroyed and another 5,000 were damaged. – The ash cloud took one year to spread around the globe, reducing global temperatures. This resulted in • Floods in 1993 along the Mississippi River • Drought in Africa in 1993 • The US had its 3rd wettest & coldest winter on record.
23. Example of Composite Volcano • Krakatau – One of the most violent eruptions in recent times occurred on an island in the Sunda Straits near Indonesia in August of 1883. – Krakatau, a volcano on the island, erupted with such force that the island disappeared.
24. Example of Composite Volcano Krakatau • Killed 36,000 people most were killed by a giant tsunami • Destroyed 160 villages • Fine ashes from the eruption were carried by upper level winds as far away as New York City • Volcanic dust lowered global temperatures for five years, this caused
25. Scientists monitor volcanoes. • Scientists monitor volcanoes to look for warning signs that an eruption may be coming. Warning signs include: – Earthquakes – Changes in the tilt of the ground – Rising temperatures of openings – Changes in volcanic gases being tested.
26. Both shield and composite volcanoes can form features called calderas, a huge crater formed by the collapse of the volcano when magma rapidly erupts from underneath it.
27. Volcanoes Affect Earth’s Land, Air, and Water
28. Materials From Volcanic Eruptions Affect Earth Land Air Water Lava Poisonous Gases* Hot Springs Volcanic Ash* Adds to Acid Rain Geysers Landslides (can Haze Fumaroles cause tsunamis) Mudflows Lower Deep –Sea Vents Temperature *These can get in the jet stream and affect the weather around the COPY THIS IN YOUR COMPOSTION world for months or years BOOK **There NOW can be PLEASE benefits: richer farmland and beautiful landscapes
29. See page 97
30. 2.4 million and 640, 000 years ago
31. See page 101
32. Fumarole
33. Deep-Sea Vent Hot Spring
34. G. Life Cycle of a Volcano 1. Active- one that is erupting or has shown signs that it may erupt in the near future 2. Dormant- volcano to awaken in the future and become active 3. Extinct-dead volcano; not likely to erupt again
35. Mt. Saint Helens
36. Resources used • Volcano World – http://volcano.und.edu/ • US Geologic Survey – http://www.usgs.gov/ • Glencoe Earth Materials & Processes • McGraw-Hill Changing Earth
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