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Lecture volcanoes.

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Awais Bakshy
Awais Bakshy

Volcanoes form at plate boundaries as molten rock, or magma, rises from below the Earth's crust. There are three main types of volcanoes: shield volcanoes which erupt fluid basalt and form wide gentle slopes, composite volcanoes which contain trapped gases and alternate between explosive and effusive eruptions forming steep slopes, and cinder cone volcanoes which have short eruptions of explosive ash and form small, steep cones. Volcanic eruptions produce hazards like pyroclastic flows, lahars, ash falls, and different types of lava. While eruptions can be locally devastating, volcanoes also create new land and leave nutrient-rich soils after erupting.

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Lecture volcanoes.
Volcanoes
~An opening in the earth's crust through which molten lava, ash, and gases are ejected. ~A mountain formed by the materials ejected from a volcano. What is A Volcano? http://dictionary.reference.com/search?q=volcano
The cause of it all… • What causes volcanoes to erupt??? • The shift in the Earth’s plates are what causes volcanoes to form. • As the plates join or separate some of the molten rock is exposed. • viscosity, resistance of a fluid to flow.
Where do volcanoes erupt? • Convergent plate boundaries – where two of Earth’s plates join together • Divergent plate boundaries – where two of Earth’s plates move apart RING OF FIRE!! • Hot spots – active areas below the earths crust
Where do volcanoes erupt???
Structure of a Volcano • Magma – the molten, or liquid-like, rock within the Earth • Lava – magma that reaches Earth’s surface • Vent – an opening through which molten (liquid- like) rock flows onto Earth’s surface • Volcanoes always have one central vent, but can also have several smaller side vents.
Structure of a Volcano magma central vent side vent lava old layers of lava ash cloud Earth’s crust
Types of Volcanoes There are three major types of volcanoes:  Shield volcanoes Composite volcanoes  Cinder cone volcanoes
Shield Volcanoes • The magma inside a shield volcano is rich in iron and magnesium and is very fluid. • Since the magma is very fluid, the lava coming out of the volcano tends to flow great distances. • When shield volcanoes erupt, the flowing lava gives the volcano the shape of a gently sloping mountain.
Shield Volcanoes • Eruptions of shield volcanoes are mild and can occur several times. • Mauna Loa in Hawaii is an example of a shield volcano.
Shield Volcanoes
Composite Volcanoes • The magma inside a composite volcano is rich in silica and much thicker than magma from a shield volcano. • Gases get trapped inside this thicker magma. • Eruptions from composite volcanoes can be flowing lava or explosions. The explosive eruptions come from the trapped gases and produce cinders and ash.
Composite Volcanoes • These different types of eruptions are what give composite volcanoes their alternating layers of lava and cinders. • Composite volcanoes have much steeper slopes than shield volcanoes. • Mount Fuji in Japan and Mount St. Helens in the USA are examples of composite volcanoes.
Composite Volcanoes
Cinder Cone Volcanoes • The magma inside a cinder cone volcano has large amounts of gas trapped in it. • Eruptions from cinder cone volcanoes are violent and explosive because of all the gas trapped in the magma. • 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.
Cinder Cone Volcanoes • Cinder cone volcanoes are usually only active for a short time and then become dormant (inactive). • Paricutin in Mexico is an example of a cinder cone volcano.
Cinder Cone Volcanoes
Volcanic Products • Pyroclastic flows • Lahars • Lava • Volcanic ash
Pyroclastic flows • Pyroclastic flows are mixtures of hot gas, ash and other volcanic rocks travelling very quickly down the slopes of volcanoes. They are one of the most dangerous hazards posed by volcanoes. • Pyroclastic flows are so hot and choking that if one is caught the person will certainly be killed. Because these flows are very fast they cannot be out-runned!
Lahars • Lahars are mudflows formed by the mixing of volcanic particles and water. • The force of a lahar is so big that buildings and valuable land may become partially or completely buried by one or more cement-like layers of rock debris (even if not crushed or carried away).
Volcanic ash • Volcanic ash is a volcanic rock which is exploded from a vent in fragments less than 2mm in size. • Volcanic ash-particles are like small sharp glass-particles that damage anything they come across. • During heavy ash-rains houses and buildings may collapse, people and animals may die by lack of oxygen.
Pahoehoe Lava • Pahoehoe lavas flow smoothly and are often formed by small volumes of hot, fluid basalt. • When the pahoehoe lava flow cools, it often solidifies to a smooth surface.
Lecture volcanoes.
Aa Lava • Aa flows are emitted from the vent at high rates ranging to 50km an hour, often with much lava fountaining. • Aa flows are animated with sporadic bursts of energy. They may push down houses, walls and forests. • However, the hallmark of aa lava flows is the very rough surface it produces when it cools and solidifies.
Volcanic Gas • Volcanic gas is contained within magma. As the magma rises to the Earth's surface the gases are released. Because some gases are toxic they can suffocate people.
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, but on the long term the ash layer, which contains many useful minerals, will be converted to a very fertile soil.
Global Impact • Sea Floor Spreading- new crust is formed at the bottom of the ocean floor.
Thanks

More Related Content

Lecture volcanoes.

  • 3. ~An opening in the earth's crust through which molten lava, ash, and gases are ejected. ~A mountain formed by the materials ejected from a volcano. What is A Volcano? http://dictionary.reference.com/search?q=volcano
  • 4. The cause of it all… • What causes volcanoes to erupt??? • The shift in the Earth’s plates are what causes volcanoes to form. • As the plates join or separate some of the molten rock is exposed. • viscosity, resistance of a fluid to flow.
  • 5. Where do volcanoes erupt? • Convergent plate boundaries – where two of Earth’s plates join together • Divergent plate boundaries – where two of Earth’s plates move apart RING OF FIRE!! • Hot spots – active areas below the earths crust
  • 7. Structure of a Volcano • Magma – the molten, or liquid-like, rock within the Earth • Lava – magma that reaches Earth’s surface • Vent – an opening through which molten (liquid- like) rock flows onto Earth’s surface • Volcanoes always have one central vent, but can also have several smaller side vents.
  • 8. Structure of a Volcano magma central vent side vent lava old layers of lava ash cloud Earth’s crust
  • 9. Types of Volcanoes There are three major types of volcanoes:  Shield volcanoes Composite volcanoes  Cinder cone volcanoes
  • 10. Shield Volcanoes • The magma inside a shield volcano is rich in iron and magnesium and is very fluid. • Since the magma is very fluid, the lava coming out of the volcano tends to flow great distances. • When shield volcanoes erupt, the flowing lava gives the volcano the shape of a gently sloping mountain.
  • 11. Shield Volcanoes • Eruptions of shield volcanoes are mild and can occur several times. • Mauna Loa in Hawaii is an example of a shield volcano.
  • 13. Composite Volcanoes • The magma inside a composite volcano is rich in silica and much thicker than magma from a shield volcano. • Gases get trapped inside this thicker magma. • Eruptions from composite volcanoes can be flowing lava or explosions. The explosive eruptions come from the trapped gases and produce cinders and ash.
  • 14. Composite Volcanoes • These different types of eruptions are what give composite volcanoes their alternating layers of lava and cinders. • Composite volcanoes have much steeper slopes than shield volcanoes. • Mount Fuji in Japan and Mount St. Helens in the USA are examples of composite volcanoes.
  • 16. Cinder Cone Volcanoes • The magma inside a cinder cone volcano has large amounts of gas trapped in it. • Eruptions from cinder cone volcanoes are violent and explosive because of all the gas trapped in the magma. • 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.
  • 17. Cinder Cone Volcanoes • Cinder cone volcanoes are usually only active for a short time and then become dormant (inactive). • Paricutin in Mexico is an example of a cinder cone volcano.
  • 19. Volcanic Products • Pyroclastic flows • Lahars • Lava • Volcanic ash
  • 20. Pyroclastic flows • Pyroclastic flows are mixtures of hot gas, ash and other volcanic rocks travelling very quickly down the slopes of volcanoes. They are one of the most dangerous hazards posed by volcanoes. • Pyroclastic flows are so hot and choking that if one is caught the person will certainly be killed. Because these flows are very fast they cannot be out-runned!
  • 21. Lahars • Lahars are mudflows formed by the mixing of volcanic particles and water. • The force of a lahar is so big that buildings and valuable land may become partially or completely buried by one or more cement-like layers of rock debris (even if not crushed or carried away).
  • 22. Volcanic ash • Volcanic ash is a volcanic rock which is exploded from a vent in fragments less than 2mm in size. • Volcanic ash-particles are like small sharp glass-particles that damage anything they come across. • During heavy ash-rains houses and buildings may collapse, people and animals may die by lack of oxygen.
  • 23. Pahoehoe Lava • Pahoehoe lavas flow smoothly and are often formed by small volumes of hot, fluid basalt. • When the pahoehoe lava flow cools, it often solidifies to a smooth surface.
  • 25. Aa Lava • Aa flows are emitted from the vent at high rates ranging to 50km an hour, often with much lava fountaining. • Aa flows are animated with sporadic bursts of energy. They may push down houses, walls and forests. • However, the hallmark of aa lava flows is the very rough surface it produces when it cools and solidifies.
  • 26. Volcanic Gas • Volcanic gas is contained within magma. As the magma rises to the Earth's surface the gases are released. Because some gases are toxic they can suffocate people.
  • 27. 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, but on the long term the ash layer, which contains many useful minerals, will be converted to a very fertile soil.
  • 28. Global Impact • Sea Floor Spreading- new crust is formed at the bottom of the ocean floor.

Editor's Notes

  1. http://library.thinkquest.org/C003124/images/volcano.jpg