1. Earth’s Layers Three main layers Crust, Mantle, and Core
The Crust Surface layer, composed of rocks that contain silicates
Two parts: Continental crust (land masses, 40km thick) & Oceanic crust (under the oceans, 7km thick)
The Mantle Layer of thick, hot rock
Can’t see into the mantle, due to light not able to travel through it
Most of the mass of earth
Mostly silicate rock, also iron and magnesium
Core Huge ball of hot metal (iron)

2. Earth’s Structure
Five layers based of physical properties (temperature, pressure, strength, and ability to flow)
Lithosphere Rock layer, includes crust and some of the upper mantle.
Not continuous, broken up into pieces Tectonic Plates
Asthenosphere Lies under the lithosphere & is made of mantle rock
Soft & flows, called plastic
Tectonic plates are carried along on the flow
Lower mantle Between the asthenosphere and outer core
Strong, rigid mantle rock, less plastic (doesn’t flow nearly as much)
Outer Core Shell of hot, liquid metal (iron) between mantle and inner core
Swirls and flows as earth rotates which produces magnetic field for the planet
Inner Core Solid sphere of hot metal (iron)
Pressure keeps core solid at the extremely high temperature (7000 degrees Celsius)

3. Earth’s Structure

4. Continental Drift vs The Theory of Plate Tectonics
Alfred Wegner Stated the world’s continents move slowly over the Earth’s surface
All Continents were once joined: Pangea
Used rock matching as evidence
Could not explain why
Harry Hess Theory of Seafloor Spreading
Process of new lithosphere created at midocean ridges (underwater mountains)
Along a rift (valley) lithosphere is moving apart & magma wells up from mantle forming new lithosphere
Old lithosphere pushed away & gravity pulls into a subduction zone (lithosphere sinking into mantle) and destroys it

5. The Theory of Plate Tectonics
The Theory States The lithosphere is divided into pieces called tectonic plates that move on top of the asthenosphere
Plates move due to seafloor widening, pushes the lithosphere away from ridges
Gravity and Earth’s internal heat drive the movement
Heat moves from warmer to cooler places Heat flows from Earth’s interior to surface producing a convection current
As lithosphere moves away it cools becomes dense enough to sink into the asthenosphere and pulls the rest of the plate (slab-pull)

6. Plate Boundaries

7. Folds & Faults
Tectonic forces produce features by producing stress on rocks- Compression, tension, or deforming
Deforming change shape
Elastically change shape temporarily
Plastic Deformation Stress on the rock exceeds elastic limit and rock is permanently deformed
Folds Bends in rock layers produced by forces of compression from the collision of tectonic plates
Folds occur in a series of arches (anticlines) and troughs (synclines)

8. Folds & Faults
Faults A break in a rock, usually move gradually past each other at faults. Rock slip with a sudden jerk= Earthquake
Occur along plate boundaries where tectonic stresses crack the crust
May slip centimeters or kilometers
Three types of faults: Normal, Reverse, & Strike-slip
Normal Rock underwent tension
Reverse Rock underwent compression
Strike-Slip Plates move horizontally

9. Seismic Waves
Earthquakes caused by the movement of plate tectonics release the energy in the form of seismic waves
Seismic Waves Mechanical waves that travel through Earth
The place where the earthquake starts is the focus seismic waves begin here a radiate out in all directions
The place on the surface directly above the focus epicenter
Two types of seismic waves: Body Waves travel through earth’s interior and are classified as either primary waves (P waves, longitudinal) or secondary waves (S waves, transverse). Surface Waves travel only on the surface
Seismic waves and density are used to determine the structure of Earth’s interior

10. Seismic Waves to determine Earth’s Interior

11. Plate Boundaries
Tectonic Plates all meet at plate boundaries Three Types Convergent, Divergent, & Transform
Divergent Plates that are pulling apart, produce stress on rock called tension
Usually occurs on seafloor and produces new lithosphere
Convergent Plates move together and produce stress on the rocks called compression, 3 types:
Continent-Continent Plates with continental crust on their leading edge collide. Both have same density so neither sinks below the other Mountains are produced
Ocean-Ocean Plates capped by oceanic crust converge. Older & denser plate subducts (goes under) beneath the younger less dense. Mantle rock partially melts in the subduction zone Volcanic islands are produced
Ocean-Continental Oceanic plates are more dense, subducts under less dense continental plate Volcanoes and mountain ranges are formed
Transform Plates slide past one another. Lithosphere is neither created or destroyed as plates move in opposite directions
Friction can be so great that rock sections get stuck and become compressed or stretched Earthquake