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How do geologic processes change the shape of Earth’s surface?

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Presentation on theme: "How do geologic processes change the shape of Earth’s surface?"— Presentation transcript:

1 How do geologic processes change the shape of Earth’s surface?

2 What do Earth’s layers consist of? Crust Mantle Core

3 Crust Layer of rock that forms Earth’s “outer skin” Includes rocks, mountains, soil, water Thin: 5-40km thick 870◦C

4 2 Types: Continental: Dry land (granite) Oceanic: Ocean (basalt)

5 Mantle Layer of hot rock 2,900km thick 2,200◦C

6 2 Sub layers: Lithosphere Asthenosphere

7 Lithosphere Rigid Much like the crust 100km thick Floats on top of the asthenosphere

8 Asthenosphere Plastic like Material can flow slowly like hot tar Has both solid & liquid qualities

9 Core Consists of iron & nickel 5,000◦C Makes up 1/3 of Earth’s mass

10 2 sub layers: Outer Core Inner Core

11 Outer Core Layer of molten material Covers the inner core 2,250km thick

12 Inner Core Dense solid ball of metal Extreme pressure does not allow Fe & Ni to spread out to form liquid 1,200km thick

13 What are the 3 ways that heat is transferred? Radiation Conduction Convection

14 Radiation Heat transferred by EM waves through space EX: Sitting by the fire!

15 Conduction Heat transferred through direct contact EX: Spoon in hot chocolate

16 Convection Heat transferred through a fluid movement of either a gas or liquid EX: Chicken noodle soup heating on the stove!

17 Which of these do you think happens in Earth’s mantle? Convection! Convection currents flow in the asthenosphere Heated material rises to the top of the mantle (lithosphere), cools, then sinks back to the bottom

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19 What does the Theory of Continental Drift state? 1910 Alfred Wegener hypothesized that all the continents had once been a single landmass A super continent called “Pangaea”

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21 Scientific Method Problem/Question Research Hypothesis Experiment Analyze Conclude

22 Supporting Evidence of Wegener’s theory Landforms Fossils Climate

23 Landforms South America & Africa have similar mountain ranges Europe & North America have similar coal fields

24 Fossils Fossil-any trace of an ancient organism that has been preserved in rock Mesoaurus fossils have been found in places now separated by oceans Glossopteris (fern like plant) fossils have been in rocks in Africa, South America, Australia, India, & Antarctica

25 Climate Spitsbergen Island lies in the Arctic Ocean, north of Norway, covered with ice Fossils of tropical plants have been discovered under the ice! South Africa-deep scratches in rock indicate glacier movement there!!!

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27 REJECTED!!! Scientists rejected Wegener’s theory of continental drift Most scientists in the 1900’s believed the Earth was cooling & shrinking causing the continents to move & mountains to form

28 Is sea-floor spreading like continental drift? 1960 Harry Hess, when studying the mid-ocean ridge, proposed that the ocean floor moved like a “conveyer belt” moving the continents with them Sea-floor spreading is the continually adding to the ocean floor

29 Sea-floor Spreading Molten material rises up from the mantle It spreads out, cools off, & hardens It pushes the older rock out on both sides of the ridge New crust forms!

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31 Wait a minute…! Hess’ idea of sea floor spreading caused scientists to revisit Wegener’s idea of continental drift!

32 So where does all of the old crust being pushed out go? Subduction: It is the process by which the ocean floor sinks beneath a deep ocean trench & back into the mantle

33 Sea Floor Spreading & Subduction… Can change the shape of the oceans! The ocean floor is renewed every 200 million years (That’s the time it takes for new crust to form, move across the ocean floor, & sink into a trench)

34 What is the Theory of Plate Tectonics? 1965 Tuzo Wilson proposed that the cracks in Earth’s surface were broken into section called “plates” He combined the idea of sea-floor spreading, Earth’s plates, & continental drift into a single theory

35 Plate Tectonics Theory A geological theory that states that pieces of Earth’s lithosphere are in constant, slow motion driven by convection currents in the mantle

36 How does it work? Lithospheric plates float on top of the asthenosphere Convection currents rise in the asthenosphere & spread out under the plates No plate can move without affecting another plate Plates move extremely slow at 1-10cm per year

37 As the plates move, collide, or pull apart…it produces GREAT changes on Earth’s surface

38 Like volcanoes, earthquakes, mountain ranges, & deep sea trenches

39 3 types of plate boundaries: Transform Divergent Convergent

40 Transform Place where 2 plates slip past each other moving in opposite directions Earthquakes often occur along these boundaries

41 Divergent Place where 2 plates move apart Most occur at the mid-ocean ridge Some occur on land creating a “rift valley” which is a deep valley Great Rift Valley in Africa is 3,000km long

42 Convergent Place where 2 plates come together Collisions of 2 plates can cause: –Oceanic to oceanic –Oceanic to continental –Continental to continental When 2 plates collide the more dense plate comes out on top!

43 Continental – Continental: mtns form Oceanic – Continental: Oceanic dives under the continent Oceanic – Oceanic: the less dense of the 2 sinks into the trench

44 What is an earthquake? Shaking & trembling that results from the movements of rock beneath Earth’s surface The movement of Earth’s plates creates stress that squeezes/pulls the rock in the crust

45 Stress A force that acts on rock to change its shape & volume 3 types of stress –Shearing –Tension –Compression

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47 Shearing Stress that pushes a mass of rock in opposite directions

48 Tension Stress that pulls on the crust stretching the rock so it becomes thinner in the middle

49 Compression Stress that squeezes rock until it folds or breaks

50 What is a fault? A break in the crust where slabs of rock slip past each other Faults usually occur along plate boundaries 3 types: –Strike-slip –Normal –Reverse

51 Strike-Slip Fault Rocks on either side of the fault slip past each other sideways Ex: San Andres Fault

52 Normal Fault The fault is at an angle One block is above the fault & the other is below it Ex: Rio Grande Rift Valley in New Mexico

53 Reverse Fault Same structure as a normal fault, but the blocks move in opposite directions Ex: Appalachian Mts

54 Where do earthquakes begin? Earthquakes occur in the lithosphere 100km below Earth’s surface The focus is point beneath the surface where the rock broke causing the earthquake The epicenter is the point on the surface right above the focus

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56 Seismic Waves During an earthquake seismic waves race out from the focus in all directions The seismic waves are greatest at the epicenter Seismograph is the instrument used to record ground movement caused by seismic waves 3 types: –P waves –S waves –Surface waves

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58 P waves Primary Waves 1 st to arrive Compress & expand the ground like an accordion

59 S waves Secondary Waves 2 nd to arrive Vibrate the ground back & forth

60 Surface Waves Come from P/S waves Move slowly Can cause the ground to roll like ocean waves

61 How do they measure the size of the quake? Magnitude is the measurement of earthquake strength based on seismic waves & movement along faults 3 ways to measure magnitude: –Mercalli Scale –Richter Scale –Moment Magnitude Scale

62 Mercalli Scale Measures the intensity Not precise

63 Richter Scale Rates the size of seismic waves using a particular seismograph Accurate measurements for nearby earthquakes

64 Moment Magnitude Scale Rates the total energy released by an earthquake near or far

65 What types of damage can a quake cause? Damage/destroy buildings Topple power lines Break water & gas lines Cause landslides Can cause aftershocks days/months later Can cause tsunamis

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71 Tsunamis Large wave that occurs when an earthquake displaces water in the ocean

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73 What causes volcanoes? A volcano is a weak spot in Earth’s crust where magma comes to the surface They form at: –Divergent boundaries –Convergent boundaries –Hot spots

74 Divergent Boundaries Most volcanoes occur here Ex: Mid-ocean ridge Volcanic belts occur along plate boundaries where lithospheric plates are weak Ex: Ring of Fire

75 Ring of Fire Major volcanic belt formed by volcanoes that rim the Pacific Ocean

76 Convergent Boundaries Island Arc-when 2 oceanic plates collide creating an arc of islands Ex: Japan, New Zealand, Caribbean Islands

77 Hot Spots Where magma rises up from the mantle melting Earth’s crust Often occur in the middle of a plate Ex: Hawaiian Islands, Yellowstone National Park

78 How do volcanoes erupt? Magma is under extreme pressure in the mantle It bubbles up through cracks in Earth’s crust Pressure decreases as magma nears Earth’s surface Lava bubbles out of the volcano

79 What does the inside of a volcano look like?

80 Magma Chamber Where magma is stored under the volcano

81 Pipe Magma moves through this long pipe that connects the magma chamber to Earth’s surface

82 Vent Opening where gas and lava leave the volcano

83 Crater Hollowed-out area at the top of a volcano

84 Volcanic Neck Magma that hardens inside the pipe

85 Dike Magma that forces itself “across” rock

86 Sill Magma that squeezes between layers of rock

87 Batholith A mass of rock formed when a large body of magma cools inside the crust

88 What are the different types of volcanoes? Shield Cone Cinder Cone Composite

89 Shield Cone Volcano

90 Cinder Cone Volcano

91 Composite Volcano

92 Volcanoes in the US Mt. Hood

93 Mt. St Helens

94 Mt. Kilauea

95 What are the stages a volcano goes through? Active→Dormant→Extinct

96 Active It’s alive! It is erupting or shows signs of erupting

97 Dormant It’s sleeping… It is expected to become active in the near future

98 Extinct Dead as a door nail. Unlikely to erupt again

99 The End!!!

100 Sike…this is the end!


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