1. Volcanoes

2. The cause of it all… What do you think causes volcanoes to erupt? The shift in the Earth’s plates are what causes volcanoes to form and erupt.Earth’s plates As the plates join or separate some of the molten rock is exposed.

3. Volcanoes of the World

4. Structure of a Volcano Magma – the molten, or liquid-like, rock within the Earth Lava – magma that reaches Earth’s surface and is exposed to O 2 (two types of lava are Pahoehoe and Aa) Lava Viscosity~ Low viscosity = water high viscosity = maple syrup Vent – an opening through which molten (liquid-like) rock flows onto Earth’s surface. Volcanoes will have many side vents through which lava will flow out of! Crater- the central opening at the top or summit of volcano. Volcanoes always have one central vent, but can also have several smaller side vents. (thickness), resistance of a liquid to flow.

5. Structure of a Volcano magma central vent side vent lava old layers of lava ash cloud Earth’s crust

6. Types of Volcanoes There are three major types of volcanoes:major  Shield volcanoes  Composite volcanoes  Cinder cone volcanoes But there is also a fourth major volcano  Lava domes

7. Shield Volcanoes The flowing lava gives the volcano gently sloping sides. They have mild Eruptions that can occur several times. The lava tends to flow great distances. The magma rich in iron (Fe) and magnesium (Mg) and is very fluid (low viscosity).

8. Shield Volcanoes Mauna Loa and Kilauea in Hawaii are examples of a shield volcanoes.

9. Composite Volcanoes They have much steeper slopes than shield volcanoes. They have alternating layers of lava and cinders. Eruptions can be flowing lava or explosions. Explosive eruptions come from the trapped gases and produce cinders and ash.

10. Composite Volcanoes The magma is rich in silica (Si) and much thicker than magma from a shield volcano. Gases get trapped inside this thicker magma. Mount Fuji in Japan and Mount St. Helens in Washington State in the US are examples of composite volcanoes.Mount St. Helens

11. Mt. Fuji (Composite Volcano) Stands over 13,000 ft. tall Surrounded by 5 lakes Last erupted in 1707-08.

12. Mount St. Helen’s Composite Volcano

13. Mount St. Helen’s before and after eruption 19791980

14. Cinder Cone Volcanoes Cinder Cones have very steep sides! Usually only active for a short time and then become dormant (inactive). ***Most Dangerous type of Volcano!*** Violent and explosive eruptions because of all the gas trapped in the magma.

15. Cinder Cone Volcanoes The magma inside a cinder cone volcano has large amounts of silica (Si) (63%) and gas trapped in it. The large amounts of hot ash and lava thrown out of the vent fall to the ground forming the cone shape that these volcanoes have. Paricutin in Mexico and Mount Vesuvius in Italy are examples of a cinder cone volcanoes.

16. Paricutin Volcano (Cinder Cone) Grew over 5 stories in the first week Continued to erupt for 8 years reaching a height of over 1,300 ft.

17. Volcanic Dangers Pyroclastic flows Lahars Lava Volcanic ash Volcanic gas Which volcanic danger kills most people? Volcanic Ash

18. Pyroclastic flows Pyroclastic flows mixtures of hot gases, ash and rocks that travel about 450mi/hr down the sides of volcanoes. Dangerous because… The poisonous gases can be as hot as 1,000 degrees. They destroy anything in its path! They are rare and don’t happen in every eruption!

19. Lahars Lahars are mudflows formed by the mixing of volcanic particles and water. Dangerous because… Carry large boulders and logs down the side of a volcanoes. Can easily crush or shear off anything in its path!

20. Damage caused from Lahars

21. Types of Lava Pahoehoe lava is runny and fast moving (up to 50 km/h). Has high iron content. Pahoehoe Lava

22. Types of Lava Aa flows are chunky and slow moving lava flows Has a high silica content Aa Lava

23. Lava Composition Which element is found most in lava? Lava is about 50% Silicon. Silicon makes lava thick (high viscosity). The more silicon you have in lava the more explosive the eruptions will be in a volcano. What is building up? Gas and pressure build up under the thick magma. Silicon!

24. Then Dangers of Lava!

25. Lava at Night!

26. Technology in Science Using infrared, scientists were able to identify specific warning signs before the eruption of the nearby Bezymianny volcano (Russia) in December 2006. Flowing lava shows up as bright yellow in an infrared image (top) of Russia's Klyuchevskoy volcano.

27. Volcanic ash Volcanic ash- small sharp glass-particles that damage anything they come across. Volcanic ash exploded from a vent in fragments less than 2mm in size. Dangerous because… Can cause houses and buildings to collapse. People and animals may die from lack of oxygen. *kills most people

28. Volcanic gas Volcanic gas is gases contained within magma. * Water Vapor is the gas that is released the most Other gases include carbon dioxide (CO 2 ), *sulfur dioxide (SO 2 ), and hydrogen sulfide (H 2 S). Dangerous because… These gases can kill people and animals and cause acid rain and contribute to greenhouse effects. Volcanoes are the largest natural polluters!

29. Global Impact When a volcano erupts it throws out a lot of ash. At short notice this ash can be very harmful to the environment by killing plants and animals. However, over a long period of time, the ash layer contains many useful minerals, that are converted into fertile soil. Volcanoes provide resources for energy extraction, also called geothermal energy. geothermal energy. Heat from the earth's crust is being converted to energy. Advantages to geothermal energy are that it is very clean and the resources are nearly inexhaustible.

30. Positives and Negatives of Volcanoes Positives Lava flows create extremely fertile soil for crops and plants. Creates new beautiful land (over long periods of time) Emits water vapor into atmosphere Create Geothermal energy Help us understand past civilizations (Pompeii) and cultures and even the Earth itself! Negatives Getting caught in volcanic dangers (blasts, lava flows, pyroclastic flows, lahars, and ash clouds) is deadly. Destroys anything in their path. Puts out large amounts of carbon dioxide (greenhouse gas) and sulfur dioxide. SO 2 is a cooling gas that can drop global temperatures after a large eruption. SO 2 also causes acid rain