Paleomagnetism
Description
For an introductory college-level earth sciences class: a review of paleomagnetism (record in the rock of the direction and intensity of Earth's magnetic field in the past) and how it's used as evidence to better understand the processes underlying plate tectonics. **This video comes at the start of the semester. For a full playlist, refer to the Oceanography or Geology playlists on the Earth Rocks! YouTube Channel. Content within this video is based on information available in any standard introductory college oceanography or geology textbook, such as Essentials of Oceanography -- Trujillo and Thurman -- OR Essentials of Geology -- Tarbuck and Lutgens -- Pearson Publishing. Part of a 7-part Plate Tectonics video series: Part 1: Earth Layers & Isostasy Part 2: Plate Tectonics Basics Part 3: Plate Tectonics Global Impacts Part 4: Plate Tectonics and California Geology Part 5: Hotspots Part 6: Paleomagnetism Part 7: Hydrothermal Vents If you are an earth science enthusiast and would like to support our ongoing video development and engage with us behind the scenes... Or if you are a student and would like access to interactive lessons built around these videos... you can do so by JOINING the Earth Rocks! YouTube Channel: https://www.youtube.com/channel/UCBEwiHo718rNAekZrqjjDjQ/join. Thank you!
The video discusses two key tools used to study plate tectonics: paleomagnetism and seafloor spreading.
Paleomagnetism refers to the record of Earth's ancient magnetic field preserved in rocks. The Earth's magnetic field is generated by convection currents in the liquid outer core. As the magnetic field changes over time, the orientation of magnetic minerals in cooling lava flows records these changes.
By studying the paleomagnetic record in volcanic rocks, scientists can reconstruct the history of the Earth's magnetic field, including periodic reversals of the north and south magnetic poles. This data is used to understand plate tectonic processes.
The video then explains how paleomagnetism was used to study seafloor spreading during World War II. Oceanographers towing magnetometers behind ships were able to detect magnetic anomalies in the seafloor basalts, indicating regions of normal and reversed magnetic polarity.
By correlating these magnetic anomalies with the known timing of magnetic field reversals, scientists were able to map out the age and spreading rate of the seafloor. This provided key evidence supporting the theory of plate tectonics and continental drift.
The video concludes by demonstrating how the paleomagnetic record can be used to calculate the speed and direction of plate motions over geological time. Overall, paleomagnetism and seafloor spreading data are powerful tools for reconstructing the history and dynamics of plate tectonics.