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:
Embryonic
Juvenile
Mature
Declining
Terminal
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.