The Dangers and Benefits of Volcanoes video 9
The Dangers and Benefits of Volcanoes video 9. 16 A volcano is a weak spot in the crust where molten material, or magma, comes to the surface. The landforms that we call volcanoes are created by repeated eruptions of lava.
Magma is the molten mixture of rock-forming substances, gases, and water that makes up part of Earth's mantle. video Most volcanoes occur along diverging plate boundaries, such as the midocean ridge, or in subduction zones around the edges of oceans.
When magma reaches the surface, it is called lava. After lava has cooled, it forms solid rock. The lava released during volcanic activity builds up Earth's surface. Volcanic activity is a constructive force that adds new rock to existing land forms new islands. video
Volcanic Eruptions During volcanic eruptions, many rock fragments are blown into the air. The smallest particles are called volcanic dust. (less than 0. 25 mm) Volcanic Ash ( 0. 25 -5 mm) falls to the Earth and forms small rocks. Volcanic bombs (a few cm to several meters) are molten and harden as they travel through the air.
Parts of a Volcano pipe - a long tube in the ground that connects the agma chamber to Earth's surface crust - the crust is Earth's outermost, rocky layer. lava - lava is molten rock; it usually comes out of rupting volcanoes. magma chamber - a magma chamber contains agma (molten rock) deep within the Earth's crust. vent - a vent is an opening in the Earth's surface hrough which volcanic materials erupt. caldera - the depression created when the roof of a agma chamber collapses. Subduction, Magma Chambers Volcanic Mountains 5. 46
Label a Volcano ash vent lava pipe crust magma chamber
Parts of a Volcano ash side vent lava pipe crust magma chamber Magma Inside the Earth 4. 45
Types of Volcanoes Different types of volcanic eruptions form different types of volcanoes. inder cones hield volcanoes omposite volcanoes
Types of Volcanoes Tall, cone-shaped mountains that are typically steeply-sided, symmetrical volcanoes in which layers of lava alternate with layers of ash. Examples of composite volcanoes include Mount Fuji in Japan and Mount St. Helens Washington state. video Composite
Composite
Mt. Vesuvius
Mount Vesuvius Images of victims in eruption of Vesuvius in 79 AD. Most died as a result of suffocation from the ash. video
Types of Volcanoes Cinder Cone Cinder cone volcanoes are the most common kind of volcanoes. They are steep sided cones. Streaming gases carry liquid lava blobs into the atmosphere that fall backto earth around a single vent to form the cone. The volcano forms when ash, cinders and bombs pile up around the vent to form a circular or oval cone. video
Cinder Cone
Types of Volcanoes At some places on Earth's surface, thin layers of lava pour out of a vent and harden on top of previous layers. Such lava flows gradually build a wide, gently sloping mountain called ashield volcano. Shield volcanoes rising from a hot spot on the ocean floor created the Hawaiian Islands. video Shield Volcano
Shield
Crater/Caldera There is often a funnel-shaped pit or depression at the top of a volcani cone. This pit is called crater. a If the crater becomes very large as a result of the collapse of its walls, it is called caldera. a A caldera may also form when the top of a volcano explodes or when the magma chamber collapses.
Volcanic Crater
Caldera
Volcanic Activity Volcanoes are rather unpredictable. Some erupt regularly, others have not erupted modern history. Scientists classify them as active, dormant or extinct.
Active Volcanoes An active volcano is one that erupts continually or periodically such as Mount Katmai in Alaska and Mount St Helens in the Cascade Range. active = constant
Dormant Volcano A volcano that has been known to erupt within modern time but is now inactive is classified as a dormant volcano. Mount Rainier in Washington state is an example of a dormant volcano in the United States. dormant = sleeping
Extinct Volcano A volcano not known to have erupted within modern history is classified as an extinct volcano. They have been worn away almost to the level of their mag chamber. Mount St. Helens was considered to be dormant but erupted after long periods of inactivity which proves that scientists can be wrong about a volcano. extinct = never
Where are the Volcanoes? Count the total amount of active volcanoes.
The Ring of Fire Most volcanoes occur along diverging plate boundaries, such as the mid-ocean ridge, or in subduction zones around the edges of oceans. video
Hawaii A hot spot is an area where magma from deep within the mantle melts through the crust like a blow torch. Hot spots often lie in the middle of continental or oceanic plates far from any plate boundaries. Unlike the volcanoes in an island arc, the volcanoes at a hot spot do not result from subduction. video
References Plate map and labeling diagram: World Book Encyclopedia Volcanoes Interfact Animated Volcano: http: //www. nsa. naples. navy. mil/disasterprep/art/volcano 2. gif Types of Volcano images: http: //dknet. lineone. net/reference/encyclopaedia/hutchinson/images/c 02745. jpg Total active volcanoes: http: //volcano. und. edu/vwdocs/frequent_questions/grp 8/question 63. html NA total: http: //www. pbs. org/wnet/savageearth/volcanoes/html/sidebar 1. html Ring of Fire total: http: //volcano. und. nodak. edu/vwdocs/frequent_questions/grp 8/question 4361. html Country totals: http: //volcano. und. nodak. edu/vwdocs/kids/volcano_project/world. html SA Total: http: //www. hrw. com/science/si- science/earth/tectonics/volcano/region 15/index. html Ring of Fire Image: http: //www. eia. doe. gov/kids/energyfacts/sources/renewable/images/RINGOFFIRE 1. gif Hawaii image: biology. usgs. gov/. . . / Pacific. Island. PIERC. htm
Attachments The_Dangers_and_Benefits_of_Volcanoes video 9. 16. asx Volcanoes_and_Lava video 2. 10. asx Yellowstone_Crater__Supervolcano. asf Subduction__Magma_Chambers__and_the_Eruption_of_Volcanoes. asf Volcanic_Mountains 5. 46. asx Magma_Inside_the_Earth 4. 45. asx Deadly_Eruptions video 6. 49. asx Mount_Vesuvius_and_Pompeii video 5. 12. asx Volcanoes 5. 31. asx Lava_Junkies 5. 42. asx The_Fire_Goddess 12. 46. asx
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