What is the Earth s interior like?

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2 What is the Earth s interior like?

3 CRUST Where we live State of matter: solid Characteristics: Rocky, Hard Rock Composition: mostly Aluminum and Silicon Thickness: 0-25 miles thick

4 Two types of crust 2 types of crust Oceanic crust: below ocean 4 miles thick Continental crust: Below the continents, mostly granite miles thick,

5 MANTLE State of matter: Semi-solid Characteristics: hot, dense, semi-solid Pressure and temperature increase as you go deeper Convection (heat) currents cause plates to move Rock Composition: mostly Iron and magnesium Thickness: 1,800 miles 80% Of Earth s volume

6 Three layers of Mantle Three layers: Lithosphere Uppermost layer relatively cool, rigid rock Made up of 7 large moving pieces and some smaller moving pieces called tectonics plates Asthenosphere- middle layer softer, weaker rock, flows slow like taffy Mesosphere bottom layer stiff rock

7 CORE State of matter: Inner core Solid Outer core- Liquid Characteristics: very high pressure Very hot c Rock composition: Iron and Nickel

8 Two layers of the core Two Layers Outer Core = hot liquid metal 1,430 miles thick Rock - nickel and iron alloy Inner core = solid metal 745 miles thick Rock - iron watch?v=3mfr2cc3erk &feature=related

9 Practice Quiz Question Can you label the following layers?

10 Why is the interior of the Earth so hot? There are three main sources of heat in the deep earth: Heat from when the planet formed Frictional heating- caused by denser core material sinking to the center of the planet Heat from the decay of radioactive elements. The interior contains radioactive isotopes. When these isotopes break apart, they release energy in the form of heat.

11 The Theory of Plate Tectonics The idea of plate tectonics was first introduced by Alfred Wegener in the early 1900 s but it was not widely accepted until the 1960 s. Plate tectonics is the theory that pieces of the Earth s lithosphere, called plates, move about slowly on top of the asthenosphere.

12 Forces causing plate movement The physical force driving these plates is not fully understood, however it appears that the lithosphere plates glide slowly on top of a semi-solid layer of the upper mantle known as the asthenosphere.

13 Forces causing plate movement Convection currents, due to the temperature differences between the mantle and the crust, hot matter will rise to the surface and cool matter will drop, which causes the plates above it to move and shift.

14 The Plate tectonics theory explains: The continents were once connected together in a large continent called Pangaea meaning all land. The continents have been and are still moving at a rate of 1-16 cm a year. ontent/visualizations/es0806/es0806page01.cfm?chapt er_no=visualization

15 Plate Tectonics

16 Movement of the Plates

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18 Evidence of Plate movement 1. Matching Coastlines (puzzle) Eastern coast of South America and Western coast of Africa fit together

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20 Gondwanaland: matching coastlines Matching Coastlines

21 Evidence of Plate tectonics 2. Shared Fossils: Same kinds of animals lived on continents that are now oceans apart

22 Evidence of Plate tectonics 3. Paleomagnetism Iron materials on ocean floor align themselves parallel to Earth s magnetic poles. A permanent records of magnetism field. Rocks retain memory of magnetic field when they cool Polar Reversals - Different aged rocks show that the polarity of the magnetic pole has reversed many times in the past.

23 Earth s magnetic poles helped to determine the plate boundaries

24 Evidence of Plate tectonics 4.Matching Glaciers

25 Evidence of Plate tectonics 5. Rocks strata (layers) match

26 Evidence of Plate tectonics 6. Matching Mountain ranges Appalachian Mountains, Greenland range, British Idles and Caledonian Mountains

27 Mechanisms of Plate Tectonics Movement Patterns: 1. Move towards each other 2. Move away from each other 3. Slide alongside each other Plate move about 1-16 cm/year

28 Earth s Tectonic Plates

29 Plate Boundaries There are three types Divergent boundaries Convergent Boundaries Transform Boundaries

30 Divergent Boundaries Two plates move apart and creates a gap of newly formed rock. In the ocean: Ridges are created as lava pushes its way up through the crust. Ex. Mid-Atlantic ridge Sea Floor spreading process where new oceanic crust is made as magma rises and old crust moves away.

31 Divergent Boundary

32 Divergent Boundary On the continent: Rift Valley: When the plates move away, the land between drops and creates a valley

33 Convergent Boundary Two plates move towards each other In the ocean: Subduction: As seafloor spreading occurs old oceanic plates sink into the mantle and creates a trench This destroys old oceanic crust Trench : where a plate sinks creating a depression

34 Plate movements

35 Convergent Boundary On the continent: Continental plates moving towards each other can form mountains Example: Himalayas

36 Building the Himalayas

37 Boundaries Review: Divergent Boundaries Plates Move away from each other Continent: Form Rift Valleys Ocean: Mid ocean ridges Convergent Boundaries Plates move towards each other Continent: Mountain ranges Ocean: Trenches

38 Transform Fault Plates slide horizontally in opposite directions. Rock is neither created or displaced, just shifted. Often creates earthquakes

39 San Andres Fault: Transform Fault

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41 What is an Earthquake? Movement of the earth s lithosphere that occurs when rocks suddenly shift, releasing stored energy. As plates move, the rocks along their edges experience immense pressure and eventually rocks are broken along the fault line. The energy is released as seismic waves. A tsunami is a large sea wave created by an underwater earthquake, volcano or landslide.

42 Earthquake Terms Fault Break in a mass of rock along which movement occurs Fold Bending in the layers of rock Focus location beneath the earth s surface where an earthquake starts Epicenter Location on the earth s surface directly above the focus

43 Types of Stress Compression - squeezes rock until it breaks. Tension pulls on the crust stretching rock Shearing pushes a mass of rock in two opposite directions

44 Normal Fault One block of rock lies above the fault and one block below it Caused by tension Types of Faults Reverse Fault The bottom block slides up past the upper block Caused by compression Strike Slip Rocks slide past each other Caused by shearing

45 Waves Energy from earthquakes is transferred through the Earth by waves P waves - Longitudinal Waves Primary wave - First wave to reach the recording station. The fastest moving wave through solid or liquid The wave looks like a compressed spring and then you release the spring.

46 Waves S Wave = Transverse Waves Secondary wave Move more slowly through rock Wave looks like a rope being shaken up and down Light and electromagnetic radiation Cannot travel through liquid

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49 Waves Surface Waves These waves move on the surface of the Earth. Move slower than S and P waves but produce larger ground movements and greater damage. They can move up and down, side to side, or like an ocean wave coming in.

50 Measuring an Earthquake Seismology: Study of earthquakes. Seismograph is a tool used to record P waves, S waves, and Surface waves. Based on the recordings, we can determine how strong the earthquake was.

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52 Seismology Three seismographs are necessary to locate the epicenter of an earthquake 1. P waves: small zigzag lines 2. S waves: larger, more ragged lines 3. Surface waves: arrive last and make the largest lines

53 How do geologists use seismographs to investigate the Earth s interior?? Certain waves move at different speeds and through certain material. (S waves can not go through liquid.) Because of this, we have figured out part of the core is liquid, the mantle is semi-liquid, etc.

54 Rating Earthquakes Richter Scale: measures the magnitude of earthquakes Moment Magnitude Scale Measures the amount of energy released by earthquake each unit represents 32X increase in the energy released. Modified Mercalli scale rates the type of damage and other effects noted by observers Largest Ever recorded 9.5 in Chile 1960

55 Modified Mercalli

56 Richter Scale

57 Example In Alaska, 1964, there was an earthquake with a magnitude of 8.4. An earthquake with a magnitude of 8 releases 810,000 times as much energy as an earthquake with a magnitude of 4.

58 Scale vs. Damage The scales cannot predict amount of damage. Damage depends on: Distance between populated areas and the epicenter. The depth of the focus. The physical properties of the surface rocks.

59 Compare the occurrence of earthquakes with the plate boundaries. Where are the earthquakes happening? (Look at the black, green and red dots.)

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61 An opening in the Earth s crust through which magma reaches Earth s surface.

62 Volcanoes Can be very destructive Have also been beneficial: Atmospheric gases Water New land Energy source Information about the inside of the Earth

63 Structure of a volcano Magma chamber where magma collects Pipe Where magma rises to the surface Conduit/Vent Tubelike structure from below the surface emerging to the surface as a vent. Crater Connected to the conduit, it is the bowl shaped pit at the top of the volcano Caldera depression at top of volcano caused by a shell collapse Lava Dome protrusion from extra lava flows

64 a. caldera

65 Mount St. Helen s c. lava dome Lava dome

66 Why volcanoes erupt Similar to shaking a pop bottle Magma is under the surface is under a lot of pressure from dissolved gases (water vapor and CO2) As it approaches the surface, the lowered pressure causes the gases to expand rapidly. An eruption occurs when the gases bubble out through a crack in the crust.

67 Magma vs Lava What is the difference?

68 Magma Under the Earth s surface. Forced upward through the vent

69 Lava When magma reaches the surface Magma cools and hardens to form lava fields

70 Eruptions Volcanoes erupt explosively or quietly depending on the magma. Explosive eruptions lava and hot gases are hurled outward and lava solidifies quickly Quiet eruptions lava erupts in a stream of easily flowing lava

71 Pahoehoe Lava flow Hot fast moving with ropelike surface

72 AA lava flow Cooler, slow lava with a chunky, crumbly appearance

73 Pillow lavaoozing lava beneath the water surface

74 Eruptions Tephra is what volcanoes throw into the air it is classified by size Ash/Dust smallest fragments of tephra Blocks Largest size pieces Cinders igneous rock similar to pumice Pyroclastic Flow Rapidly moving clouds of tephra with hot gas (up to 700 ) at speeds up to 80 mph

75 Types of Volcanoes Shield Volcanoes Broad, gentle sloping shape Quiet, mild eruptions Largest volcanoes Ex. Mauna Loa

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77 Types of Volcanoes Composite Volcanoes Tall with steep sides Built from alternating layers of ash, cinder and lava Explosive eruptions Often have secondary vents Ex. Mt Fuji, Japan

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80 Types of Volcanoes Cinder Cone Smallest and most abundant Steep sides Explosive eruption is entirely of ash and cinders Active only for a short time, then dormant Ex. Paracutin, Mexico

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83 Sunset crater, AZ

84 Mt. Pelée, Martinique

85 Locations of volcanoes Two places most volcanoes reside Plate boundaries Hot spots Hot spots occur in the middle of plates - region where hot rock extends from deep within the mantle (ex. Hawaii, Iceland)

86 80% of all volcanoes are located in the Ring of Fire

87 Active, dormant, extinct An active volcano is a volcano that has had at least one eruption during the past 10,000 years. An active volcano might be erupting or dormant. An erupting volcano is an active volcano that is having an eruption. A dormant volcano is an active volcano that is not erupting, but supposed to erupt again. An extinct volcano has not had an eruption for at least 10,000 years and is not expected to erupt again in a comparable time scale of the future.

88 Mauna Loa 1984 (Photograph by Richard B. Moore)

89 Hekla, Iceland 1991, photo by Sigurgeir Jónasson

90 Hekla, Iceland 1991, photo by Ragnar Th. Sigurdsson

91 Mauna Loa (Peter Francis)

92 1,900-foot high fountain, Kilauea Iki,1959 (National Park Service Photograph)

93 Stromboli, April 1996

94 Vulcano,Vulcanello, and Lipari (Peter Francis)

95 1980 eruption of Mount St. Helens (photo courtesy of J.M. Vallance)

96 Mt. St. Helens most recent eruption

97 Eyjafjallajökull Iceland