Plate Tectonics

Evidence Supporting Continental Drift and Seafloor Spreading

Paleomagnetism

• Rocks with iron-rich minerals that have formed millions of years ago were magnetized by the magnetic field of the Earth and are aligned parallel to the Earth's magnetic field.

  

  Polar Wandering

• Polar Wandering
  • When examining lava flows, it was noted that the direction of the iron-rich minerals were in numerous orientations.
  • The likely explanation was that the continents moved.
  • The unlikely explanation is that the poles wandered throughout the Earth over time.

  

  Magnetic Reversal

• Magnetic Reversals and Seafloor Spreading
  • Rocks that exhibit magnetism that matches the current magnetic field of the Earth are said to have normal polarity.
  • Rocks with the opposite magnetism of the Earth are said to have reverse polarity.

Earthquake Patterns

• After plotting the distribution of Earth's earthquakes, it was apparent that the earthquake zones correlated with suspected plate boundaries.

Ocean Drilling

• A deep-sea drilling project showed that the oldest sea floor was found at the continental edges of the oceans and the youngest sea floor was found at the ridge crest.

Hot Spots

• A concentrated area of heat in the mantle of the Earth.
• The hot spots are found in the middle of a plate and are capable of producing magma.
• If given enough time, the magma forms an island.
• Example: Hawaiian Islands