Transcript File
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 •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 •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 Copy the picture. Outline: Crust- brown Mantle- red Core- orange Lightly color Earth’s physical divisions. Use a different color for each. Pangea Theory •All continents originally one land mass: Pangea 245 million years ago •Wegener’s Hypothesis: continental driftsingle 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; continentaloceanic; 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 Deformation: Stress on Rocks •Compression- forces squeeze rock; occurs at convergent boundaries •Tension- forces stretch rock; occurs at divergent boundaries •Folding- rock bends because of stress 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) 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 S Waves •Shear/ secondary waves •Second fastest •Stretch rock sideways •Cannot travel through liquid/ bend around the outer core 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 Seismographs determine: •Magnitude: the size of the earthquake (Richter Scale) •Depth: how deep the earthquake was •Location: where the earthquake occurred