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)

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)

Earth’s Structure

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

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)

Plate Boundaries

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)

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

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

Seismic Waves to determine Earth’s Interior

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