Earth’s Structure

Earth has three main layers. Crust Mantle Core Layers are different because of their chemical composition

Crust We live on top of here. Thinnest layer: <1% of Earth’s mass Continental and oceanic crusts Minerals and rocks found here

Mantle Under the crust Makes up most of Earth’s mass: about 67% Denser than the crust Sometimes mantle rock pushes to the surface (magma)

Core Center of Earth About 33% of Earth’s mass Densest and hottest layer Made of iron and nickel

Physical Structure of Earth Lithosphere- crust and rigid upper mantle; tectonic plates Asthenosphere- soft rock of the mantle; how tectonic plates move Mesosphere- between outer core and asthenosphere Outer core- completely liquid; iron and nickel Inner core- solid and dense; iron and nickel

Copy the picture. Outline: Crust- brown Mantle- green Core- purple Lightly color Earth’s physical divisions. Lithosphere: blue Asthenosphere: orange Mesosphere: red Outer core: yellow Inner core: brown

Pangea Theory All continents originally one land mass: Pangea 245 million years ago Wegener’s Hypothesis: continental drift- single land mass broke up many times over the years and moved to where they are now

Tectonic Plates Pieces of the lithosphere that can move Sit on top of asthenosphere

Tectonic Plate Boundaries Convergent- plates collide Ex: continental-continental; continental- oceanic; oceanic-oceanic Divergent- plates separate Ex: sea-floor spreading Transform- plates slide past each other Ex: San Andreas Fault in CA

Subduction occurs at convergent boundaries with oceanic crust.

Continental-Continental collisions can sometimes form mountains.

Sea-Floor Spreading Happens at mid-ocean ridges (underwater mountain chains) Sea-floor spreading: new oceanic lithosphere forms when magma rises to the surface and becomes solid This happens because tectonic plates spread apart

What can happen at boundaries? Convergent- earthquakes, volcanoes, mountains Divergent- earthquakes, volcanoes Transform- earthquakes

Faults Rock layers can break with stress Faults- where rocks break and slide past each other There’s always a fault at a transform boundary (ex: San Andreas) Faults can be at other places (ex: New Madrid runs through Memphis) https://www.youtube.com/watch?v=SjqVidNX23o

Earthquakes Seismology- study of earthquakes Seismic waves- energy waves that travel away from earthquakes Body waves (P and S) Surface Waves- travel slowly and are very destructive

P Waves Pressure/primary waves Travel through solids, liquids, and gases Fastest First waves detected

Cannot travel through liquid/ bend around the outer core S Waves Secondary waves Second fastest Stretch rock sideways Cannot travel through liquid/ bend around the outer core https://www.youtube.com/watch?v=BxtiKodKq_E

Seismographs determine: •Magnitude: the size of the earthquake (Richter Scale) •Depth: how deep the earthquake was •Location: where the earthquake occurred

https://www.youtube.com/watch?v=Gbd1FcuLJLQ

Magnitude Estimated Effects Effects of Different-Sized Earthquakes 2.0 can be detected only by seismograph 3.0 can be felt at epicenter 4.0 can be felt by most people in the area 5.0 causes damage at epicenter 6.0 can cause widespread damage 7.0 can cause great, widespread damage https://www.youtube.com/watch?v=xyKgamjegtQ

Volcanoes Magma rises because magma is less dense than the rock around it Occur at mid-ocean ridges, subduction zones, and hotspots Hotspots are not at plate boundaries https://www.youtube.com/watch?v=jG-Sy0y08GM https://www.youtube.com/watch?v=bYv6V5EJAKc