EARTH SCIENCE KESSEL

Transcription

1 EARTH SCIENCE KESSEL

2 Bell Ringer List everything you KNOW about a volcano (at least 3 things). Then list everything you WANT to know about volcanoes (at least 2 things).

3 Bell Ringer What evidence might you look for if you think a volcanic eruption has occurred?

4 Bell Ringer Explain how the idea of plate tectonics influences earthquakes and volcanoes.

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6 Bell Ringer From what we have talked about previously, what do you think the Earth s interior is like?

7 Layers Defined by Composition Earth s interior consists of three major zones defined by their chemical composition the crust, mantle, and core.

8 Earth s Layered Structure

9 Layers Defined by Composition Crust Composed mainly of oxygen and silicon Varies in thickness - About 7 km in oceanic regions - Continental crust about 8-40 km - Exceeds 70 km in mountainous regions

10 Layers Defined by Composition Mantle Composed mainly of silicate rocks rich in magnesium and iron About 2900km thick - Contains lithosphere, asthenosphere and mesosphere.

11 Layers Defined by Composition Outer Core Composed of nickel-iron alloy About 2180km thick Outer core is liquid in nature

12 Layers Defined by Composition Inner Core Composed of iron About 1220km thick Inner core is solid in nature

13 Earth s Layered Structure

14 Layers Defined by Physical Properties Lithosphere Made up of the crust and uppermost mantle (about 100 km thick) Cool, rigid, solid layer that behaves like solid rock

15 Layers Defined by Physical Properties Asthenosphere Beneath the lithosphere, above the mesosphere. About 700km thick Soft, weak layer that is easily deformed.

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17 Bell Ringer List the layers of Earth that you know of AND then explain how you think scientists know these layers.

18 9.1 Continental Drift An Idea Before Its Time Albert Wegener was a German born polar researcher, geophysicist and meteorologist. He is famous for his hypothesis of continental drift.

19 An Idea Before Its Time Wegener s continental drift hypothesis stated that the continents had once been joined to form a single supercontinent, Pangaea.

20 Pangaea

21 Breakup of Pangaea

22 An Idea Before Its Time Evidence Rock Types and Structures - Evidence of continental drift exists in the form of several mountain belts that end at one coastline, only to reappear across the ocean.

23 Matching Mountain Ranges

24 An Idea Before Its Time Evidence The Continental Puzzle

25 An Idea Before Its Time Evidence Matching Fossils - Fossil evidence for continental drift includes several fossil organisms found on different landmasses.

26 Glacier Evidence

27 Rejecting the Hypothesis A New Theory Emerges Wegener could not provide an explanation of exactly what made the continents move. New technology lead to findings which then lead to a new theory called plate tectonics.

28 Earth s Major Roles A plate is one of numerous rigid sections of the lithosphere that move as a unit over the material of the asthenosphere.

29 Types of Plate Boundaries Divergent boundaries are the places where two plates move apart.

30 Types of Plate Boundaries Convergent boundaries form where two plates move together.

31 Types of Plate Boundaries Transform fault boundaries are where two plates grind past each other without the production or destruction of the lithosphere.

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33 Bell Ringer Has Earth s surface (the continents) always looked the way it does now? Explain your answer in 2-3 sentences.

34 Divergent Boundaries Rift Valleys and Seafloor Spreading Rift valleys are deep faulted structures found along the axes of divergent plate boundaries.

35 Divergent Boundaries Rift Valleys and Seafloor Spreading Seafloor spreading produces new oceanic lithosphere.

36 Convergent Boundaries A subduction zone occurs when one oceanic plate is forced down into the mantle beneath a second plate.

37 Convergent Boundaries Denser oceanic slab sinks into the asthenosphere. Oceanic-Continental Pockets of magma develop and rise. Continental volcanic arcs form by volcanic activity caused by the subduction of oceanic lithosphere beneath a continent.

38 Oceanic-Continental Convergent Boundary

39 Convergent Boundaries Oceanic-Oceanic Two oceanic slabs converge and one descends beneath the other. This kind of boundary often forms volcanoes on the ocean floor. Volcanic island arcs form as volcanoes emerge from the sea.

40 Oceanic-Oceanic Convergent Boundary

41 Convergent Boundaries Continental-Continental When subducting plates contain continental material, two continents collide. This kind of boundary can produce new mountain ranges, such as the Himalayas.

42 Continental-Continental Convergent Boundary

43 Collision of India and Asia

44 Transform Fault Boundaries Transform faults Most join two segments of a mid-ocean ridge. At the time of formation, they roughly parallel the direction of plate movement. They aid the movement of oceanic crustal material.

45 Transform Fault Boundary

46 Evidence for Plate Tectonics Hot Spots A hot spot is a concentration of heat in the mantle capable of producing magma, which rises to Earth s surface. Hot spot evidence supports that the plates move over the Earth s surface.

47 Hot Spot

48 Causes of Plate Motion The unequal distribution of heat within Earth causes the thermal convection in the mantle that ultimately drives plate motion. Convective flow is the motion of matter resulting from changes in temperature.

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50 Bell Ringer Explain, in your own words, how mountains are formed.

51 Earthquakes An earthquake is the vibration of Earth produced by the rapid release of energy Focus and Epicenter Focus is the point within Earth where the earthquake starts. Epicenter is the location on the surface directly above the focus.

52 Earthquakes Faults Faults are fractures in Earth where movement has occurred.

53 Slippage Along a Fault

54 Cause of Earthquakes Elastic Rebound Hypothesis Most earthquakes are produced by the rapid release of elastic energy stored in rock that has been subjected to great forces.

55 Elastic Rebound Hypothesis

56 Cause of Earthquakes Aftershocks and Foreshocks A foreshock is a small earthquake that often precedes a major earthquake. An aftershock is a small earthquake that follows the main earthquake.

57 Cause of Earthquakes Aftershocks and Foreshocks

58 Earthquake Tools Seismographs are instruments that record earthquake waves.

59 Earthquake Tools Seismograms are traces of amplified, electronically recorded ground motion made by seismographs.

60 Earthquake Waves Surface waves are seismic waves that travel along Earth s outer layer.

61 Earthquake Waves Body Waves P waves Travel through solids, liquids, and gases Have the greatest velocity of all earthquake waves

62 Earthquake Waves Body Waves S waves Seismic waves that travel along Earth s outer layer Travel only through solids

63 Measuring Earthquakes Scientists have used two different types of measurements to describe the size of an earthquake: intensity and magnitude. Richter Scale Based on the amplitude of the largest seismic wave

64 Measuring Earthquakes Momentum Magnitude Most widely used measurement for earthquakes because it estimates the energy released by earthquakes.

65 Earthquake Magnitudes

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67 Bell Ringer Earthquakes are caused by the Earth shaking. Can you feel all earthquakes? Explain.

68 Seismic Vibrations The damage to buildings and other structures from earthquake waves depends on the intensity and duration of the vibrations, the nature of the material on which the structure is built, and the design of the structure.

69 Earthquake Damage

70 Seismic Vibrations Building Design Factors that determine structural damage - Intensity of the earthquake - Unreinforced stone or brick buildings are the most serious safety threats - Nature of the material upon which the structure rests - The design of the structure

71 Seismic Vibrations Liquefaction Saturated material turns fluid

72 Tsunamis A tsunami triggered by an earthquake occurs where a slab of the ocean floor is displaced vertically along a fault.

73 Tsunamis Tsunami Warning System Large earthquakes are reported to Hawaii from Pacific seismic stations. Although tsunamis travel quickly, there is sufficient time to evacuate all but the area closest to the epicenter.

74 Other Dangers Landslides With many earthquakes, the greatest damage to structures is from landslides and ground subsidence, or the sinking of the ground triggered by vibrations. Fire In the San Francisco earthquake of 1906, most of the destruction was caused by fires that started when gas and electrical lines were cut.

75 Landslide Damage

76 8.3 Destruction from Earthquakes Predicting Earthquakes Short-Range Predictions So far, methods for short-range predictions of earthquakes have not been successful. Long-Range Forecasts Scientists don t yet understand enough about how and where earthquakes will occur to make accurate long-term predictions. A seismic gap is an area along a fault where there has not been any earthquake activity for a long period of time.

77 8.4 Earth s Layered Structure Discovering Earth s Layers Moho Velocity of seismic waves increases abruptly below 50 km of depth Separates crust from underlying mantle Shadow Zone Absence of P waves from about 105 degrees to 140 degrees around the globe from an earthquake Can be explained if Earth contains a core composed of materials unlike the overlying mantle

78 Earth s Interior Showing P and S Wave Paths

79 Seismic Waves Paths Through the Earth

80 Bell Ringer Describe the similarities between an earthquake and a tsunami.

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82 Bell Ringer Based off of your knowledge of plate tectonics, how do you think volcanoes are formed?

83 Anatomy of a Volcano A volcano is a mountain formed of lava and/or pyroclastic material

84 Anatomy of a Volcano A crater is the depression at the summit of a volcano. A conduit, or pipe, carries gas-rich magma to the surface.

85 Anatomy of a Typical Volcano

86 Types of Volcanoes Shield Volcanoes Shield volcanoes are broad, gently sloping volcanoes.

87 Types of Volcanoes Cinder Cones Cinder cones are small volcanoes built primarily of pyroclastic material ejected from a single vent. Small in size; occur in groups

88 Cinder Cones

89 Types of Volcanoes Composite Cones Composite cones are volcanoes composed of both lava flows and pyroclastic material. Most are adjacent to the Pacific Ocean Large size; most violent activity

90 Composite Cones

91 Mount St. Helens Before and After the May 18, 1980, Eruption

92 Profiles of Volcanic Landforms

93 Volcanic Material Pyroclastic Materials Pyroclastic materials is the term given to particles produced in volcanic eruptions.

94 Volcanic Material Pyroclastic Materials The fragments ejected during eruptions range in size from very fine dust and volcanic ash to pieces that weigh several tons.

95 Pyroclastic Materials

96 Volcanic Material Pyroclastic Materials Types of pyroclastic material - Ash and dust fine, glassy fragments - Pumice frothy, air-filled lava - Lapilli walnut-sized particles - Cinders pea-sized particles Particles larger than lapilli - Blocks hardened lava - Bombs ejected as hot lava

97 Factors Affecting Eruptions Viscosity Viscosity is the measure of a material's resistance to flow. Factors affecting viscosity Temperature (hotter magmas are less viscous) Composition (silica content)

98 Factors Affecting Eruptions Dissolved gases Mainly water vapor and carbon dioxide Violence of an eruption is related to how easily gases escape from magma Gases escape easily from fluid magma. Viscous magma produces a more violent eruption.

99 10.3 Plate Tectonics and Igneous Activity Convergent Plate Boundaries The basic connection between plate tectonics and volcanism is that plate motions provide the mechanisms by which mantle rocks melt to generate magma. Ocean-Ocean Rising magma can form volcanic island arcs in an ocean (Aleutian Islands). Ocean-Continent Rising magma can form continental volcanic arcs (Andes Mountains).

100 Convergent Boundary Volcano

101 10.3 Plate Tectonics and Igneous Activity Divergent Plate Boundaries The greatest volume of volcanic rock is produced along the oceanic ridge system. Lithosphere pulls apart, partial melting occurs, and large quantities of fluid basaltic magma are produced.

102 10.3 Plate Tectonics and Igneous Activity Intraplate Igneous Activity Intraplate volcanism is igneous activity that occurs within a tectonic plate away from plate boundaries. Most intraplate volcanism occurs where a mass of hotter than normal mantle material called a mantle plume rises toward the surface. The activity forms localized volcanic regions called hot spots. Examples include the Hawaiian Islands and the Columbia Plateau.

103 Kilauea, an Intraplate Volcano