I. Layers Defined by Composition 8.4 Earth’s Layered Structure  A) Earth’s interior consists of 3 major zones (chemical composition).

Defined by Composition 8.4 Earth’s Layered Structure  1)Crust Continental crust a) Continental crust - Upper crust composed of granitic rocks

8.4 Earth’s Layered Structure  1)Crust Oceanic crust b) Oceanic crust - 1) Basaltic composition - 2) Younger than the continental crust

8.4 Earth’s Layered Structure  2) Mantle a) Below crust.  3) Core a) Below mantle b) Composed of an iron-nickel alloy c) Really dense

II. Defined by physical properties 8.4 Earth’s Layered Structure  1) Lithosphere a) Crust and uppermost mantle (about 100 km thick) b) Cool, rigid, solid

8.4 Earth’s Layered Structure a)Beneath the lithosphere b) Upper mantle c) Soft, weak layer that is easily deformed  2) Asthenosphere

8.4 Earth’s Layered Structure  3) Lower Mantle a) More rigid layer b) Rocks are very hot and flow like a milkshake.

8.4 Earth’s Layered Structure

 4) Inner Core a) Behaves like a solid Fe & Ni  5) Outer Core a) Liquid layer b) Convective flow of metallic iron within generates Earth’s magnetic field

Earth’s Layered Structure

Discovering Earth’s Layers 8.4 Earth’s Layered Structure Separates crust from underlying mantle  Moho- boundary ˇ ´

Earth’s Interior Showing P and S Wave Paths

Discovering Earth’s Composition 8.4 Earth’s Layered Structure  Mantle  Crust Early seismic data and drilling technology indicate that the continental crust is mostly made of lighter, granitic rocks. Composition is more speculative. Some of the lava that reaches Earth’s surface comes from asthenosphere within.