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Transcript
POS Unit 5: Planet Earth Topic 4 The Moving Crust Our earth is made up of different layers: 1. Atmosphere “vapour” (air) 2. Hydrosphere “water” (oceans, rivers, lakes) 3. Lithosphere “rocky” (land) 4. Asthenosphere “weak” (molten layer under lithosphere, the mantle) 5. Biosphere: living layer (plants/animals) *Although the earth may seem very large, the layers we inhabit, and require for our very survival are extremely thin. Our planet is more fragile (viewed from the moon) than we think. As small as we are, humans can bring about major environmental changes. How thin is the earth’s crust, the lithosphere? It is like the shell on an egg, or the skin of an apple …very thin relative to the rest Inside our planet Layers: Oceanic and Continental Crust (lithosphere) 5km-60 km deep Mantle (1000-4000oC) (asthenosphere) upper (more solid) and lower mantle (more liquid) layer of molten rock, reason for movement of tectonic plates, volcanoes, earthquakes Core (5500-6000oC) Outer-liquid iron Fe and nickel Ni (responsible for our magnetic field Inner-solid *relative temperatures Question: Why is the center of the earth solid? * The inner core should be a gas, seeing how the temperature is so high (materials expand as particles move farther apart) but the high pressure keeps the inner core solid Alfred Wegener Hmm… did they ever fit together? Movement The crust is moving, as it floats in pieces on the mantle Why is the crust moving? Convection currents! Movement: Continental drift Pieces: tectonic plates But why are they moving? Convection Currents The SUPERCONTINENT PANGAEA *Pick out the continents *Why is Asia mostly under water? Gondwanaland/Laurasia How old is the earth? 4.5 billion years When did the dinosaurs go extinct? 65 million years ago Continental Drift Evidence: 1-Shapes fit together supercontinent Pangaea -broke into Laurasia and Gondwanaland 2-still moving today measure distances, see the trenches, areas of sea floor spreading 3-common fossils Present day Three major types of movement Transform Fault Slipping past eachother The San Andreas Fault California, US Converging Plates Moving towards eachother 2 options: Mountain building (continental crust crashing into continental crust) Subduction (continental crust sliding on top of oceanic crust) Results: Earthquakes Volcanic eruptions Mountain formation Convergence of Tectonic Plates: Continental and Oceanic crust Ring of Fire (Pacific) The Pacific oceanic crust is subducting underneath the continental crust of surrounding plates This causes widespread earthquakes and volcanic activity Ex) Japan, Philippines, California, Seattle (Mt. St. Helens) *Convection Currents Hot gases/liquids rise, as the particles of that material become less dense, and float on the colder, more dense liquids/gases https://www.youtube.com/watch?v=ryrXA GY1dmE 1. Sea floor spreading 2. Subduction 3. Mountain formation *Convergent or divergent? Mid Atlantic Ridge Sea-floor spreading Pushing apart North and South America from Africa and Europe at a rate of ~2cm a year Divergent boundaries Diverging plates Sea-floor spreading Summary Geysers-Old faithful Yellowstone National Park Deep Ocean Vents Activities Activity pg 386 Give me a clue Answer Q’s #1-4 in your journals Glue map pieces in your journal “fitting together” Activity pg 388 What do the rocks tell us? Answer Q’s 1-3 and “What did you find out?” in your journal Activity pg 389 The Spreading Sea Floor Answer “What did you find out” questions #1-3 in your journals Tape/staple the paper into your journal Assignments Vocabulary Update journals Topic 4 Evidence of plate tectonic movement Technologies Topic 4 Q’s pg 394 #1-5 Faces of Earth Video Disc A, Episode 1: Building the planet 0:00-3:00 Intro 3:00 (skip)- Avaris camera- high altitude plane, lydar camera START 8:20 Formation of earth in space 4.5 billion years ago 10:20 magnetic field + aurora, need it to keep the atmosphere/hydrosphere/biosphere 16:00- beginning of atmosphere/hydrologic cycle=hydrosphere 17:30=life 3 billion years ago, cyanobacteria’s waste product was oxygen (1st photosynthesis!) ozone 20:00-skip iron, other more complex life 26:00 extinctions Faces of Earth cont. Disc A, Episode 1: Building the planet 26:00 PT permian extinction: 95% of all life! Volcanism, Pangaea, altered atmosphere Noah’s ark? 28:00 65 million years ago KT Cretaceous/Tertiary extinction Asteroid Dinosaurs, 50% of all life 30:00 Fossil fuels Coal formation by compressed peat (plant debris) Natural Gas and Oil by microorganisms in the oceans 33:00 (stop) rocks for oil + gas research, seismic Faces of Earth cont. Disc A, Episode 2: Shaping the planet START 0:00 Intro: Divergent boundary in Ethiopia (Iceland only other one on land), plate tectonics 5:00-9:40 skip, tribe, monitoring, GPS 11:00 tectonic plates 13:00 mid Atlantic ridge 14:00 ice age 15:00-18:30 skip salt 18:30 convergent mountain building, subduction 23:00 volcanoes : Mt Vesuvius (Pompeii, Herculaneum) 27:00 normal fault 28:00 skip prediction 33:40 Himalayas, seismo, earthquakes 38:00 California, San Andreas Fault 42:00 P, S waves 44:00 END Faces of Earth Disc B Episode 1: Assembling America Mount Rainier erupts, Seattle WA Subduction, water in volcanoes=explosive Cascade range Earthquake + seismograms Ultralight aircraft over scab-land (monster flood) Salt lake Utah Yellowstone Geysers…some truth to supervolcano Great Lakes Appalachian mountains (Himalaya sized in Pangaea) 31:00 comet crashed Faces of Earth Disc B Episode 2: A human world (boring!) Weather, climates, ice ages Ice cores Caused by change in earth’s orbit around the sun, or wobble of the earth’s axis Cultural evolution as part of environmental change Metallurgy, mining Global warming … now it is us who are changing the face of earth by construction + demolition