Earth Layers & Isostasy
Description
For an introductory college-level earth sciences class: a review of Earth's layers -- crust, mantle, inner core, outer core, asthenosphere, lithosphere -- including their thicknesses, compositions, and basic properties (+the description of the moho: the boundary between the crust and mantle). We also discuss how the Earth's crust and lithosphere rise and fall isostatically as weight is added or removed. **This video comes near the beginning 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 the principles of plate tectonics, which is the dynamic process that shapes the Earth's surface, causing volcanoes, earthquakes, and major mountain ranges. It first reviews the basic layers of the Earth - the core, mantle, and crust.
The core is made mostly of iron and is divided into a solid inner core and a liquid outer core. The crust is very thin, with denser oceanic crust and less dense continental crust. The mantle, which makes up most of the Earth's volume, has a plastic-like asthenosphere layer that allows the overlying lithosphere (crust plus upper mantle) to sink into it, similar to how icebergs float in water.
This sinking of the denser oceanic lithosphere and floating of the less dense continental lithosphere is called isostasy. Seismic waves reveal the boundary between the crust and mantle, called the Moho. As material is added or removed from the crust, the Earth's surface adjusts isostatically, causing uplift or subsidence.
Overall, the video provides a detailed overview of the Earth's internal structure and how the dynamic processes of plate tectonics shape the surface features we observe.