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3:48 AM Plate Tectonics. 3:48 AM Plate Tectonics.

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Presentation on theme: "3:48 AM Plate Tectonics. 3:48 AM Plate Tectonics."— Presentation transcript:

1 3:48 AM Plate Tectonics

2 3:48 AM Plate Tectonics

3 3:48 AM Mechanism of Plate Tectonics

4 3:48 AM Cross-section of Atlantic Ocean

5 3:48 AM Directions and Rates of Plate Motion

6 3:48 AM By about 1900, advances in geology, biology and geochemistry (primarily radioactivity) â Earth is billions of years old. â Earth is dynamic - The rocks and landforms that we see today evolved over a very long history, including: mountain building erosion sedimentation metamorphism etc. Geology in the Early 1900’s

7 3:48 AM Geologic Time Scale 4.5 Billion 540 Million (= Billion) 540 Million

8 3:48 AM Age of the Earth Oldest Rocks on Earth ( ) 4.6 Billion Years 20 million years 6,000 years 1, billion 10, ,000 1,000,000 10,000, million 1 billion

9 3:48 AM By about 1900, advances in geology, biology and geochemistry (primarily radioactivity) â Earth is billions of years old. â Earth is dynamic - The rocks and landforms that we see today evolved over a very long history, including: mountain building erosion sedimentation metamorphism etc. However, until the second half of the 20th century, most models of the evolution of the Earth involved: Vertical Tectonics Very few geologists believed that large scale horizontal motions could occur. It was thought that the physical properties of Earth materials could not permit such motions. Continental Drift ??

10 3:48 AM Very few geologists believed that large scale horizontal motions could occur. It was thought that the physical properties of Earth materials could not permit such motions. Until the second half of the 20th century, most models of the evolution of the Earth involved: Vertical Tectonics Continental Drift ??

11 3:48 AM Rock Cycle

12 3:48 AM Mountain Building and Erosion

13 3:48 AM Alfred Wegener

14 3:48 AM : Continental drift proposed by Alfred Wegener : Continental drift debated : Stalemate : Revival of interest in continental drift Paleomagnetism Ocean Floor Exploration (Mid-ocean ridges/young age of oceanic crust) 1962: High heat flow over mid-ocean ridges/convection (H. Hess) 1963: Magnetic anomalies parallel to mid-ocean ridges (F. Vine and D. Matthews) 1965: Transform faults and earthquake locations in ocean basins (J.T. Wilson) 1968: Earthquake locations and direction of earthquake motion consistent with plate motion (J. Oliver, B. Isacks and L. Sykes) 1970-?: Plate tectonics accepted by most geoscientists Stages in the Development of Plate Tectonics

15 3:48 AM Although several people had proposed continental drift as far back as the 1600’s, such an hypothesis was not generally accepted. In 1912, a German climatologist named Afred Wegener published a book entitled Origin of Continents and Oceans in which he proposed an hypothesis of continental drift and listed supporting evidence for it. Wegener’s evidence came from: Reconstruction of ancient climates Similar fossils on widely separated continents Matching rock structures across ocean basins Geometrical fit of continental margins Alfred Wegener and Continental Drift

16 3:48 AM Directions and Rates of Plate Motion

17 3:48 AM Wegener proposed that an original super-continent that he called Pangaea (“all land”) existed before continental drift began about 180 million years ago.

18 3:48 AM

19 According to Wegener’s hypothesis, South America and Africa began to drift apart about 70 million years ago.

20 3:48 AM Breakup of Pangaea

21 3:48 AM Geophysicists countered Wegener’s argument: They argued that physical properties of Earth materials would not permit that much horizontal motion.

22 3:48 AM : Continental drift proposed by Alfred Wegener : Continental drift debated : Stalemate : Revival of interest in continental drift Paleomagnetism Ocean Floor Exploration (Mid-ocean ridges/young age of oceanic crust) 1962: High heat flow over mid-ocean ridges/convection (H. Hess) 1963: Magnetic anomalies parallel to mid-ocean ridges (F. Vine and D. Matthews) 1965: Transform faults and earthquake locations in ocean basins (J.T. Wilson) 1968: Earthquake locations and direction of earthquake motion consistent with plate motion (J. Oliver, B. Isacks and L. Sykes) 1970-?: Plate tectonics accepted by most geoscientists Stages in the Development of Plate Tectonics

23 3:48 AM Reconstruction of ancient climates Similar fossils on widely separated continents Matching rock structures across ocean basins Geometrical fit of continental margins Wegener’s Evidence for Continental Drift

24 3:48 AM Glacial Ice Today 18,000 years ago

25 3:48 AM Pangaea - Glacial Ice

26 3:48 AM Reconstruction of Ancient Climates

27 3:48 AM Climate Zones

28 3:48 AM Similar Fossils

29 3:48 AM Fossil Distribution

30 3:48 AM Explanation of Fossil Evidence

31 3:48 AM Similar Rock Structures

32 3:48 AM Fig. 3.06a W. W. Norton. Modified from Hurley.

33 3:48 AM W. W. Norton

34 3:48 AM Reconstruction of Pangaea

35 3:48 AM : Continental drift proposed by Alfred Wegener : Continental drift debated : Stalemate : Revival of interest in continental drift Paleomagnetism Ocean Floor Exploration (Mid-ocean ridges/young age of oceanic crust) 1962: High heat flow over mid-ocean ridges/convection (H. Hess) 1963: Magnetic anomalies parallel to mid-ocean ridges (F. Vine and D. Matthews) 1965: Transform faults and earthquake locations in ocean basins (J.T. Wilson) 1968: Earthquake locations and direction of earthquake motion consistent with plate motion (J. Oliver, B. Isacks and L. Sykes) 1970-?: Plate tectonics accepted by most geoscientists Stages in the Development of Plate Tectonics

36 3:48 AM Fossil Distribution

37 3:48 AM Wegener’s Mechanism for Continental Drift

38 3:48 AM The Earth’s Crust

39 3:48 AM By the early 1900’s, seismologists had already discerned the general structure and physical properties of the Earth’s interior.

40 3:48 AM P and S Wave Paths

41 3:48 AM

42 M=7.6, ∆=97° Boston, Massachusetts - First Wave Arrives 4:04 (13 minutes) Magnitude 7.6 PAKISTAN, October 08, 2005 at 03:51 UTC

43 3:48 AM  Distanced measured in degrees from epicenter. Travel-time versus Distance

44 3:48 AM M=6.7, ∆=25° Magnitude 6.8 CAYMAN ISLANDS, December 14, 2004 at 23:20 UTC Boston, Massachusetts - First Wave Arrives 23:26 (6 minutes)

45 3:48 AM M=7.8, ∆=62° Magnitude 7.8 TARAPACA, CHILE, June 13, :45 UTC Boston, Massachusetts - First Wave Arrives 22:55 (10 minutes)

46 3:48 AM

47 6371 km Path Distance (km) Time (sec) Velocity 1 2, km/sec 2 6, km/sec 3 9, km/sec

48 3:48 AM Crust 6-7 km/sec Mantle 8-13 km/sec Outer Core 8-10 km/sec Inner Core km/sec P-wave Velocities

49 3:48 AM Crust 6-7 km/sec Mantle 8-13 km/sec Outer Core 8-10 km/sec Inner Core km/sec P-wave Velocities Air: 0.3 Water: 1.4 Concrete: 3.6 Granite: Iron: 5.8 Aluminum: 6.6

50 3:48 AM Crust: Granite/Basalt Mantle: Peridotite Outer Core: Liquid Iron Inner Core: Solid Iron Composition of Earth’s Interior

51 3:48 AM Andrija Mohorovicic analysed records of an earthquake in Croatia - discovered the existence of the “mantle” underneath the continental “crust”.

52 3:48 AM Granite Basalt Peridotite

53 3:48 AM Wegener’s Mechanism for Continental Drift

54 3:48 AM Mechanism of Plate Tectonics

55 3:48 AM : Continental drift proposed by Alfred Wegener : Continental drift debated : Stalemate : Revival of interest in continental drift Paleomagnetism Ocean Floor Exploration (Mid-ocean ridges/young age of oceanic crust) 1962: High heat flow over mid-ocean ridges/convection (H. Hess) 1963: Magnetic anomalies parallel to mid-ocean ridges (F. Vine and D. Matthews) 1965: Transform faults and earthquake locations in ocean basins (J.T. Wilson) 1968: Earthquake locations and direction of earthquake motion consistent with plate motion (J. Oliver, B. Isacks and L. Sykes) 1970-?: Plate tectonics accepted by most geoscientists Stages in the Development of Plate Tectonics

56 3:48 AM


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