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© Boardworks Ltd 2005 1 of 35 Volcanoes These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates.

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Presentation on theme: "© Boardworks Ltd 2005 1 of 35 Volcanoes These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates."— Presentation transcript:

1 © Boardworks Ltd of 35 Volcanoes These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates the slide contains activities created in Flash. These activities are not editable. For more detailed instructions, see the Getting Started presentation. 1 of 35 © Boardworks Ltd 2005

2 2 of 35 What is a volcano? Why do volcanoes occur? Where are volcanoes found? What happened in the 1980 Mount St Helens eruption? Can volcanic eruptions be predicted? Why do people live in volcanic areas? Learning objectives

3 © Boardworks Ltd of 35 A volcano is an opening or vent in the earth’s surface through which molten material erupts and solidifies as lava. Volcanic vent What is a volcano?

4 © Boardworks Ltd of 35 Volcanic bombs, ash, lava, gases Magma chamber Parasitic cone Crater Main vent Label this cross section of a volcano

5 © Boardworks Ltd of 35 Crater Volcanic bombs, ash and gases Main vent Parasitic cone Magma chamber Cross section of a volcano

6 © Boardworks Ltd of 35 Cross section of a volcano

7 © Boardworks Ltd of 35 Volcanic emissions

8 © Boardworks Ltd of 35 Volcanic emissions

9 © Boardworks Ltd of 35 Active volcano – liable to erupt e.g. Mt Etna. Dormant (sleeping) volcano – a volcano which has not erupted for many years. For example, Mt Pinatubo erupted in 1991 after 500 years of dormancy. Extinct volcano – a volcano which has not erupted for many thousands or millions of years e.g. Edinburgh. However, it is often very difficult to tell whether a volcano will erupt again…El Chichon, Mexico erupted in 1982 after being dormant for approximately 1200 years! Do all volcanoes erupt?

10 © Boardworks Ltd of 35 What is a volcano? Why do volcanoes occur? Where are volcanoes found? What happened in the 1980 Mount St Helens eruption? Can volcanic eruptions be predicted? Why do people live in volcanic areas? Learning objectives

11 © Boardworks Ltd of 35 A destructive plate boundary is found where a continental plate meets an oceanic plate. The oceanic plate descends under the continental plate because it is denser. As the plate descends it starts to melt due to the friction caused by the movement between the plates. This melted plate is now hot, liquid rock (magma). The magma rises through the gaps in the continental plate. If it reaches the surface, the liquid rock forms a volcano. Why do they happen?

12 © Boardworks Ltd of 35 Destructive plate boundary

13 © Boardworks Ltd of 35 At a constructive plate boundary, two plates move apart. As the two plates move apart, magma rises up to fill the gap. This causes volcanoes. However, since the magma can escape easily at the surface, the volcano does not erupt with much force. Why do they happen?

14 © Boardworks Ltd of 35 Constructive plate boundary

15 © Boardworks Ltd of 35 Volcano shapes Why do volcanoes have different shapes?

16 © Boardworks Ltd of 35 Volcano shapes

17 © Boardworks Ltd of 35 Volcanic activity at plate margins

18 © Boardworks Ltd of 35 What is a volcano? Why do volcanoes occur? Where are volcanoes found? What happened in the 1980 Mount St Helens eruption? Can volcanic eruptions be predicted? Why do people live in volcanic areas? Learning objectives

19 © Boardworks Ltd of 35 Around which plate do we find most volcanoes? Where are volcanoes found?

20 © Boardworks Ltd of 35 The Hawaiian islands are a chain of volcanoes in the Pacific Ocean. Hawaii Look at their location on the map below. Why is this an unusual place for them to be located?

21 © Boardworks Ltd of 35 Hot spot volcanoes In the animation above, why are the volcanoes to the left of the ‘hot spot’ extinct?

22 © Boardworks Ltd of 35 What is a volcano? Why do volcanoes occur? Where are volcanoes found? What happened in the 1980 Mount St Helens eruption? Can volcanic eruptions be predicted? Why do people live in volcanic areas? Learning objectives

23 © Boardworks Ltd of 35 Mt St Helens is located on the ‘Ring of Fire’. Mt St Helens eruption (May 1980) Internet Links

24 © Boardworks Ltd of 35 Mt St Helens is located on a destructive plate boundary where a continental plate (North American) meets an oceanic plate (Juan de Fuca). Mt St Helens – causes of the eruption Juan de Fuca plate North American plate Which plate is denser? Describe what happens when the oceanic plate descends under the continental plate.

25 © Boardworks Ltd of 35 Mt St Helens – the eruption

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29 © Boardworks Ltd of 35 Mount St. Helens woke up on March 20, 1980, with a Richter magnitude 5.1 earthquake. Steam venting started on March 27. By the end of April, the north side of the mountain started to bulge. With little warning, a Richter magnitude 5.1 earthquake triggered a massive collapse of the north face of the mountain on May 18. This was the largest known debris avalanche in recorded history. The magma inside of St. Helens burst forth into a large-scale pyroclastic flow which flattened vegetation and buildings in an area of over 230 square miles (600 km²). This eruption was a 5 on the Volcanic Explosivity Index scale. For more than nine hours, a vigorous plume of ash erupted, eventually reaching 12 to 15 miles (20 to 25 km) above sea level. The plume moved eastward at an average speed of 60 miles per hour (95 km/h), with ash reaching Idaho by noon. The collapse of the northern flank of St. Helens mixed with ice, snow, and water to create lahars (volcanic mudflows). The lahars flowed many miles down the Toutle and Cowlitz Rivers, destroying bridges and lumber camps. A total of 3.9 million cubic yards (3.0 million cubic meters) of material was transported by the lahars. By around 5:30 PM on May 18 the vertical ash column declined in stature but less severe outbursts continued through the night and the following several days. In all, St. Helens released an amount of energy equivalent to 27,000 Hiroshima-sized atomic bombs and ejected more than a cubic kilometre of material. The removal of the north side of the mountain reduced St. Helens' height by about 1300 feet (400 m) and left a 1 to 2 mile (1.6 to 3.2 km) wide and 0.5 mile (800 m) deep crater with its north end open in a huge breach. Fifty-seven people were killed along with 1500 elk, 5000 deer, and an estimated 11 million fish. In addition, 200 homes, 47 bridges, and 185 miles (300 km) of highway were destroyed.

30 © Boardworks Ltd of 35 VEIDescription Plume Height VolumeClassificationHow oftenExample 0non-explosive< 100 m1000s m3HawaiiandailyKilauea 1gentle m10,000s m3Haw/StromboliandailyStromboli 2explosive1-5 km1,000,000s m3Strom/VulcanianweeklyGaleras, severe3-15 km10,000,000s m3VulcanianyearlyRuiz, cataclysmic10-25 km100,000,000s m3Vulc/Plinian10's of yearsGalunggung, paroxysmal>25 km1 km3Plinian100's of yearsSt. Helens, colossal>25 km10s km3Plin/Ultra-Plinian100's of yearsKrakatau, super-colossal>25 km100s km3Ultra-Plinian1000's of yearsTambora, mega-colossal>25 km1,000s km3Ultra-Plinian10,000's of yearsYellowstone, 2 Ma

31 © Boardworks Ltd of 35 N 010km Mt St Helens – consequences of the eruption

32 © Boardworks Ltd of 35 BEFORE AFTER Mt St Helens – consequences of the eruption

33 © Boardworks Ltd of 35 What damage did the eruption cause?

34 © Boardworks Ltd of 35 What benefits might the volcanic activity have brought to Mt St Helens? Why do you think animals such as the vole and gopher survived the blast? How did their survival benefit the area? Mt St Helens – consequences of the eruption

35 © Boardworks Ltd of 35 What is a volcano? Why do volcanoes occur? Where are volcanoes found? What happened in the 1980 Mount St Helens eruption? Can volcanic eruptions be predicted? Why do people live in volcanic areas? Learning objectives

36 © Boardworks Ltd of 35 Predicting eruptions

37 © Boardworks Ltd of 35 The problem of prediction Volcanologists (people who study volcanoes) are skilled at predicting the likelihood of an eruption. However, it's very difficult to pinpoint exactly when an eruption will happen. Often, moving magma doesn't result in an eruption, but instead cools below the surface. Monitoring potential eruptions is expensive. With many volcanoes erupting only every few hundred years, it's not possible to monitor every site.

38 © Boardworks Ltd of 35 Precautions during an eruption

39 © Boardworks Ltd of 35 What is a volcano? Why do volcanoes occur? Where are volcanoes found? What happened in the 1980 Mount St Helens eruption? Can volcanic eruptions be predicted? Why do people live in volcanic areas? Learning objectives

40 © Boardworks Ltd of 35 Tourists are attracted to areas of volcanic activity. Geothermal energy can be produced in many volcanic areas. Can you think of any other reasons? This lava is weathered (broken down) to form a fertile soil. Why do people live in volcanic areas?

41 © Boardworks Ltd of 35 Virtual field visits The Michigan Technological University Volcanoes Page Global Volcanism Program Fallout: Eye on the Volcano Savage earth Volcano World - a fun and informative web site Internet links


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