3_OCE 3008_Chapter 2 Pt1

Page 1: Important Dates and Announcements

• For late registrants:

  • Email the instructor to change quiz availability until 11:30 PM on January 17th (Friday).

• Midterm #1 is scheduled for February 4th and covers Chapters 1-4.

Page 2: Chapter Overview

• Topic: Plate Tectonics and the Ocean Floor

Page 3: Key Learning Objectives

• Summarize evidence supporting continental drift and plate tectonics theory.

• Discuss origins and characteristics of different types of plate boundaries.

• Explain how plate tectonics clarifies geological processes and ocean features.

• Understand how the arrangement of land and oceans has changed and will continue to evolve.

Page 4: Theory of Plate Tectonics

• Definition: thin rigid plates of the Lithosphere move horizontally.

• Origin: Proposed by Alfred Wegener in 1912 as “Continental Drift.”

Page 5: Pangaea and Panthalassa

• Wegener's hypothesis: One large supercontinent, Pangaea, existed 200 million years ago, surrounded by Panthalassa, one vast ocean.

• Included the Tethys Sea.

Page 6: Evidence of Continental Drift

• Wegener noted puzzle-like fit of continents, though gaps existed.

• 1960s corroboration by Sir Edward Bullard using 2000m depth contours to match continents.

Page 7: Rock Similarities

• Wegener searched for matching sequences of rock units and ancient mountain chains.

• Found similar rock types, ages, and structures on different continents.

Page 8: Glacial and Climate Evidence

• Evidence of glaciation in tropical regions suggests land movement:

  • Possible ancient glacial ice age ~300 million years ago refuted by coal evidence.

  • Tropical continents once closer to poles.

Page 9: Glacial Flow Patterns

• Patterns and directions of glacial flow suggest continents were once configured differently.

• Glaciers flowed from the South Pole into warmer regions.

Page 10: Fossil Evidence

• Fossils indicate ancient different climates:

  • Fossil palm trees in the Arctic.

  • Coal deposits in Antarctica.

  • Coral fossils found in regions now cold.

Page 11: Biogeographical Evidence

• Distribution of organisms corroborates continental drift:

  • Identical fossils on separated continents (e.g., Mesosaurus, Glossopteris).

  • Modern organisms with similar ancestries, such as marsupials.

Page 12: Wegener’s 1915 Publication

• Published "The Origins of Continents and Oceans" proposing gravitational and tidal forces as driving mechanisms for continental movement.

• Faced criticism for suggesting continental rocks could 'plow' oceanic crust.

• Although his mechanism was incorrect, his hypothesis about continental drift was validated.

Page 13: Current Evidence for Plate Tectonics

• Evidence lines include:

  • Orientation of magnetic particles, apparent polar wandering, magnetic polarity reversals, ocean floor anomalies.

  • Sea floor spreading and earthquake distribution data.

  • Satellite data confirms plate motion.

Page 14: Earth's Magnetic Field

• Earth has a magnetic field generated by convective movement in the outer core.

• Magnetic properties recorded in igneous rocks; magnetite aligns with the Earth's field.

Page 15: Understanding Paleomagnetism

• Paleomagnetism studies Earth's ancient magnetic field; indicates where rocks formed based on their captured magnetic field data.

• Considers magnetic dip in rocks relative to latitude of formation.

Page 16: Apparent Polar Wandering

• Magnetic dip data suggests two separate poles observed when rocks from different locations were analyzed.

• Conclusion: Continents, not poles, have moved.

Page 17: Magnetic Pole Reversals

• Earth’s magnetic poles reverse approximately every 450,000 years with the last reversal occurring 780,000 years ago.

• Magnetic particles in rocks capture the magnetic field's strength and orientation, including reversals.

Page 18: Tracking Magnetic Pole Movement

• 184 reversals noted in the last 83 million years.

• The magnetic north pole's movement currently averages ~50 km/year.

Page 19: Paleomagnetism and Ocean Floor Studies

• Before 1955, paleomagnetic studies mainly concerned terrestrial findings.

• Use of magnetometers to examine how ocean floor rocks affected the magnetic field resulted in patterns of magnetism along the ocean floor.

Page 20: Contributions by Harry Hess

• Harry Hess, a submarine captain and geologist noted key ocean features, including mountain ridges and trenches.

• Proposed the role of convection cells in asthenosphere as a driving mechanism for sea-floor spreading.

Page 21: Mid-Ocean Ridge Dynamics

• Mid-ocean ridge serves as a spreading center where new oceanic crust forms.

• Ridges create new crust as they split apart and move towards subduction zones.

Page 22: Characteristics of Mid-Ocean Ridges

• Continuous underwater mountain ranges which rise over 2.5 km off the ocean floor and are volcanic in origin.

• Consistent formation of new ocean floor at ridge axes indicates ongoing sea-floor spreading.

Page 23: Subduction Zones

• Define areas where oceanic trenches exist, resulting in crust destruction.

• Slab Pull and Slab Suction create plate motion, triggering significant geological phenomena.

Page 24: Deep Ocean Trenches

• Represent the ocean's deepest regions; major earthquakes occur here as a result of tectonic plates interacting.

Page 25: Vine and Matthews’ Analysis

• Frederick Vine and Drummond Matthews analyzed igneous rock patterns around mid-ocean ridges, linking magnetic polarity with sea-floor spreading.

Page 26: Coral Sea Floor Study Findings

• The combination of Vine and Matthews' findings with Hess's sea-floor spreading led to strong evidence for continental drift.

Page 27: Evidence from Deep-Sea Drilling

• Conducted to validate sea-floor spreading through radiometric dating of ocean rocks.

• Found a symmetrical pattern of age distribution at mid-ocean ridges; the oldest ocean floor is about 180 million years old.

Page 28: Age Distribution Patterns

• The Atlantic Ocean exhibits a symmetric age pattern; the Mid-Atlantic Ridge separated Pangaea.

• The Pacific Ocean shows a less symmetric pattern due to many subduction zones.

Page 29: Heat Flow Dynamics

• Heat from Earth's interior is rapidly released at mid-ocean ridges; average heat flow significantly exceeds that of other regions.

Page 30: Earthquake Activity at Subduction Zones

• Most large earthquakes occur at subduction zones; activity aligns with tectonic plate boundaries.

Page 31: Global Plate Boundaries

• Major tectonic plates include Pacific, North American, South American, Eurasian, African, Antarctic, and Australian.

Page 32: Satellite Technology in Plate Tectonics

• Satellite measurements substantiate predictions of plate movement, generally averaging between 2-12 cm/year.

Page 33: Application of Plate Tectonic Theory - Wilson Cycle

• Predicts the life cycle of ocean basins:

  1. Embryonic

  2. Juvenile

  3. Mature

  4. Declining

  5. Terminal

  6. Suturing

• Indicates the comprehensive nature of plate tectonics compared to continental drift in explaining surface movements and features.

Page 34: Conclusion Key Concepts

• The significance of evidence supporting continental drift and plate tectonics, characteristics of plate boundaries, and the evolving configuration of Earth's land and oceans.