Earth's Interior Composition and Structure

Earth's Interior Composition and Structure

• Earth's interior has three compositional layers: crust, mantle, and core.
• The core is extremely deep and incredibly hot, making direct sampling impossible.
• Deep layers are hotter.

Comparing Compositional and Structural Models

• Structural Model: This model focuses on physical properties (like temperature, rigidity, flow) of Earth's layers. Layer names include lithosphere, asthenosphere, mesosphere, outer core, and inner core.
• Compositional Model: This model focuses on chemical composition (minerals, rocks) of Earth's layers. Layer names include crust, mantle, and core.

Crust vs. Lithosphere

• Similarities: Both can be studied through earthquakes and volcanic eruptions.
• Differences: The crust is the outermost layer of Earth. The lithosphere includes the crust and upper rigid mantle.

Mantle Study Challenges

• Directly studying the mantle is difficult due to its great depth.
• Undifferentiated stony meteorites offer clues. These are small objects that cooled and solidified so fast, they didn't completely separate into distinct layers by density.

Earth's Mantle and Crust Density

• The mantle is denser than the crust due to a higher proportion of heavier elements and compression caused by the crust's weight.

Earth's Internal Structure and Convection

• Earth's inner layers are primarily heavier elements. Outer layers have a wide variety of elements in their rocks.
• Convection in Earth's outer core and mantle is driven by temperature differences. Hotter, less dense materials rise, cooler, denser materials sink, creating a circulation pattern (convection cells).
• Inner core doesn't convect due to its high pressure despite high temperature.

Processes Shaping Earth's Surface

• Processes include weathering, erosion, and both solar and internal energy.

Fossil Formation and Preservation

• Most fossils are found in sedimentary rocks, as water buries organic remains.
• Body Fossils: These are the actual remains of organisms.
• Replacement: Organisms are buried and become replaced with minerals, forming fossils.
• Casts, Molds, and Imprints: These structures are formed when a decay remains of organism produces a three-dimensional mark.
• Soft-Part Preservation: Requires specific environments for preservation of non-mineralized tissues (e.g., poor acidity).
• Trace Fossils: Signs of an organism's activity (like footprints).