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Notes Points

Notes Points. Name __________________________________ Period _______. Chapter 13 Standard. 3e. Students know there are two kinds of volcanoes: one kind with violent eruptions producing steep slopes and the other kind with voluminous lava flows producing gentle slopes. Chapter 13 – Volcanoes.

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Notes Points

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  1. Notes Points Name __________________________________ Period _______

  2. Chapter 13 Standard 3e. Students know there are two kinds of volcanoes: one kind with violent eruptions producing steep slopes and the other kind with voluminous lava flows producing gentle slopes.

  3. Chapter 13 – Volcanoes

  4. Review!! • Plate tectonics is the theory that explains why and how continents move and is the study of the formation of features in Earth’s crust. • The lithosphere is the thin, rigid, outer shell of Earth that is the crust and part of the mantle. • Lithosphere is broken into several blocks called tectonic plates. • Some volcanoes form when plate motions generate magma that erupts on Earth’s surface.

  5. I. 13.1 – VOLCANOES AND PLATE TECTONICS

  6. A. Formation of Magma • Magma is the liquid (melted) rock that forms under Earth’s surface. • Magma is formed under three conditions: • Temperature increases above melting point and the rock will melt. • With less pressure, the melting point decreases and the rock will melt. • With the addition of fluids, the melting point will decrease and the rock will melt.

  7. B. Magma and Volcanism • Volcanism is any activity that includes movement of magma onto Earth’s surface. • Magma rises to Earth’s surface because it is less dense (lighter) than the surrounding rock.

  8. Magma becomes larger at the surface in two ways: • Magma can melt surrounding rock. • Magma is forced into cracks and crevices of surrounding rock.

  9. GASES LAVA MAGMA • Lava is magma at the Earth’s surface. • Volcano is the vent in Earth’s surface through which magma and gases are expelled (escape). Color and label picture.

  10. C. Parts of a Volcano • Ash cloud – the cloud of ash and dust that form in the air after some volcanic eruptions • Conduit – a passage through which magma (molten rock) flows in a volcano • Crust – earth's outermost, rocky layer • Lava – Magma that reaches the earth’s surface • Magma chamber – contains magma (molten rock) deep within the Earth's crust • Side Vent – a vent in the side of a volcano • Vent (central) – opening in the Earth's surface through which volcanic materials erupt

  11. Vent Conduit Lava Crust Side Vent Color and label picture.

  12. D. There are three major volcanic zones where most active volcanoes occur. • Subduction Zone – one tectonic plate goes under another plate • Occurs along lithospheric plates • There are two types of subduction zones: • oceanic-continental – where oceanic crust subducts under continental crust; volcanoes form on the continental crust next to the ocean and results in a volcanic arc

  13. Oceanic-Continental Subduction Color and label picture.

  14. Oceanic-Oceanic Subduction • oceanic-oceanic – where oceanic crust subducts under oceanic crust; volcanoes form on ocean crust and results in an island arc of volcanoes Color and label picture.

  15. Color picture. • Example of subduction zone: PACIFIC RING OF FIRE

  16. Mid-Ocean Ridges – tectonic plates are moving away from each other • Occur along lithospheric plates. • Site of where there is the greatest amount of magma that comes to the surface. • The interconnected mid-ocean ridges that circle the earth form a major zone of volcanic activity. • As plates pull apart, magma wells upward along the rift zone and can form underwater volcanoes.

  17. Hot Spots – area of volcanism within lithospheric plates • Hot spots remain stationary, but plate above it slowly drifts so that eventually a chain of volcanoes getting younger in age form • Example of hot spots: Hawaiian Islands Color picture.

  18. Write 10 questions for this section. Highlight key words and phrases. Draw a picture.

  19. Summary (one paragraph) – Page 3 The lithosphere is ______________. Magma is _________________________. Volcanism is _________________. Magma rises to the surface because it is ____________________. Lava is __________________________. The three major volcanic zones are ____________, ______________, and ______________.

  20. II. 13.2 – VOLCANIC ERUPTIONS

  21. A. Viscosity can be used to describe magma and lava. • Viscosity – the internal resistance to flow • Example: honey is more viscous than water and moves slower than water • The higher the temperature of the magma or lava, the lower the viscosity (fast moving). • The higher the silica content (crystalline molecule), the higher the viscosity (slow moving).

  22. B. There are three types of magma. • basaltic magma • andesitic magma • rhyolitic magma

  23. Types of Magma Copy table.

  24. C. There are two types of lava. • mafic lava – dark colored when hardened and is rich in magnesium and iron • felsic lava – lighter colored when hardened and has little amounts of magnesium and iron, is rich in silica

  25. D. There are three types of lava flows. • Pahoehoe – Solidified mafic lava with a wrinkled surface

  26. Aa lava – jagged chunks of lava formed by rapid cooling on the surface of a lava flow

  27. Blocky lava – forms chunky volcanic rock when it cools.

  28. E. There are volcanic rock fragments that are released. • Felsic lava explodes, throwing pyroclastic material into the air • Pyroclastic material – rock fragments ejected from a volcano • pyroclastic material is sometimes called TEPHRA

  29. Pyroclastic Material

  30. F. There are three types of volcanoes. • Shield Volcanoes – broad at the base and have gently sloping sides • Covers a wide area and generally results from nonexplosive lava eruptions • Layers of hot mafic lava flow out of vent, harden, and slowly build up to form the cone

  31. Cinder Cone Volcanoes – very steep slopes and are not very tall • Result from explosive pyroclastic eruptions • Made of solid fragments ejected from the volcano

  32. Lava Pyroclastic Material Lava Pyroclastic Material • Composite Volcanoes / Stratovolcanoes – alternating layers of lava and pyroclastic material • Has both quiet eruptions and explosive eruptions • THEY NEVER BOTH erupt at the same time, the lava layer will erupt, then the pyroclastic layer and so on. • Examples: Mt Fuji (Japan) and Mt St Helens (Washington)

  33. G. Craters and Calderas • Crater – the funnel shaped pit at the top of a volcanic vent • Craters are formed when material is blown out of the volcano by explosions • When the magma chamber below a volcano is emptied, the volcanic cone may collapse, leaving a large, basin-shaped depression called a caldera.

  34. H. Scientists use clues to help predict volcanic eruptions. • Use seismographs to detect small earthquakes that may be triggered by magma moving upward. • Watch for slight bulging of surface of a volcano. • Indications of dangerous amounts of gases in air by volcanoes.

  35. Write 10 questions for this section. You should have a total of 20 questions. Highlight key words and phrases. Draw a picture.

  36. Summary (one paragraph) – Page 4 Viscosity is ___________________. The two types of lava are _________ and __________. The three types of lava flow are __________, __________, and ____________. Pyroclastic material is _______________________. The three types of volcanoes are __________ which has ___________________, ___________ which has ____________________, and _____________ which has ________________.

  37. Notes Points Name __________________________________ Period _______ J. Nguyen – Physical Science

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