Earths Interior Study Guide.pdf

Study Guide: The Earth's Interior 1. Basic Structure of the Earth Crust: o The outermost and thinnest layer. For the most part, silicates with lower MgO content than the mantle. o Two types: Oceanic crust (denser, basaltic rocks high in magnesium and iron)...

Study Guide: The Earth's Interior 1. Basic Structure of the Earth Crust: o The outermost and thinnest layer. For the most part, silicates with lower MgO content than the mantle. o Two types: Oceanic crust (denser, basaltic rocks high in magnesium and iron) and Continental crust (less dense, similar to granite). o Together WITH the upper mantle, they form the lithosphere, which is colder, brittle, and broken into tectonic plates. Mantle: o Largest layer by volume, situated between the crust and core. o Composed mainly of silicates (minerals with silicon and oxygen). o Divided into two parts: ▪ Lower mantle: Solid but deforms and flows over time due to high pressure. ▪ Asthenosphere: Solid but behaves like a viscous liquid, allowing for tectonic plate movement. Core: o Earth's innermost layer, consisting of iron and nickel. o Divided into: ▪ Inner core: Solid despite high temperatures due to immense pressure. ▪ Outer core: Liquid, responsible for generating Earth's magnetic field through convection currents. 2. Seismic Waves and Their Role Seismic Waves: o Wave front: Boundary between the rock through which a wave has passed and rock it hasn’t. o Seismic rays: Imaginary points marking the position of waves. Seismic-Wave Propagation: o The velocity of seismic waves depends on the material they pass through. o Seismic waves travel faster through solids and slower through liquids. o S-waves cannot travel through liquids, a key to understanding Earth's inner composition. o Seismic waves move faster in denser material 3. Reflection and Refraction of Waves When seismic waves hit a boundary between materials, they can: o Reflect: Bounce off the boundary. o Refract: Bend as they pass through the boundary. o Seismic waves bend towards faster media and away from slower ones. 4. Crust-Mantle Boundary (Moho) Discovered in 1919 by Andrija Mohorovičić, based on seismic wave velocities. Important for understanding how seismic waves behave as they pass through different layers of Earth. The findings point out that seismic rays can move arrive earlier to far stations if they travel through the mantle 5. Structure of the Mantle The low-velocity zone (LVZ) occurs beneath oceanic crust (100–200 km). Seismic-wave velocity increases with depth in the mantle. 6. The Core and Core-Mantle Boundary S-wave shadow zones indicate that S-waves do not travel through liquid, helping to determine the liquid nature of the outer core. P-wave shadow zones further help scientists determine the boundaries between the core and mantle. 7. Seismic Tomography Creates 3-D images of Earth's interior using variations in seismic velocities. Seismic reflection profiling reveals the crust's structure and stratigraphy. Key Concepts: 1. Earth's Interior Composition: Understanding the core, mantle, and crust provides insights into seismic activity, plate tectonics, and Earth's magnetic field. 2. Seismic Waves: These are essential tools for exploring Earth's inner layers, as their speed and behavior help identify the composition and state (solid or liquid) of the layers. 3. Boundary Dynamics: The reflection and refraction of seismic waves at different boundaries reveal important transitions between Earth's layers, such as the Moho and core-mantle boundary.