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Transcript
Earth’s Layered Structure The story so far…… Evidence of Earth’s Layers and their composition PHENOMENON: What did you observe? What evidence do you have? OBJECTS: Define the system. What objects are interacting? Rocks of Earth’s crust vary in density: granite is less dense, then basalt, peridotite and iron Density of Earth’s Rocks Lab Molten lava erupts from volcanoes. Mohorovic found that EQ wave velocities change at about 50 km. Magma video clip EQ P waves are reflected, bent, velocity decreases and S-waves are stopped. Earthquake P and S waves Earth has a north and south magnetic pole. Compass, Temperature, density and velocity changes at certain depths: (100 km, 1000 km, 3000 km, 5000 km) Ave. density of the crustal rocks ; granite, basalt, peridotite is 3.0 g/cc. Yet the average density of the entire Earth is 5.4 g/cc Meteorites formed from the same materials at the same time as the terrestrial planets. Some of them are rocky and some are metallic EQ waves were found to reflect, bounce off “something” solid in the center MOTION: Describe the motion that in the model that explains your observations EARTH’S CRUST is made of rocky material got “sorted” by density when Earth was a young molten planet. More dense iron sank to center and less dense basalt and granite are on top. Magma suggests that there is liquid, MANTLE of molten rock under the solid, rocky crust There is a boundary between the solid crust and the liquid (magma) mantle layer. magnets Earth has an OUTER CORE composed of liquid IRON that is flowing creates a magnetic field. Rock Lab data The Earth’s INNER CORE must be very dense metal (iron 7.9 g/cc and nickel 8.9 g/cc) to average out to 5.4 g/cc Meteorite samples The inner core is SOLID iron and nickel The Earth’s Interior (pg. 72) Mantle: Outer core: Lithosphere Continental Crust Ocean Crust Inner core: Earth’s layer are Determined by these properties: 1. 2. 3. Top Earth elements: 1. 2. 3. 4. 5. Asthenosphere So….Earth’s 4 layers were determined by physical properties…. 1. Temperatures and pressures (both increase and change with greater depth) 2. Physical properties (density, chemicals and elements) 3. Mechanical behavior (how the material moves or doesn’t move: solid or liquid) Earth’s Main Layers • • • • Lithosphere/crust Mantle Outer Core Inner Core Outer core Inner core Crust / Lithosphere (pg. 72) • • • • • “litho-” stone, “-sphere” circle Contains the crust and upper mantle Relatively cool Rigid, brittle, shell Depth – Ave. 100 km or 60 miles Continental Crust • Cold, brittle, fractures (earthquakes) • Averages 35-40 km (25 miles ) thick – Can exceed 70 km (40 mi) in mountains! • Rock types: – Upper crust is mostly light, silicate rocks such as granite rock – Up to 4 billion years old! – 2.7 g/ml density Oceanic Crust • 7 km (5 miles ) THIN • Composed of dark, igneous rock – Basalt (black, ocean basin) – 180 million years young (or less) 3.0 g/ml density • • • • upper mantle 100 km to 660 km Soft, solid/liquid, weak in structure, constantly moving Asthenosphere (asthenos- weak) Interaction between lithosphere and asthenosphere • But the lithosphere sits “floats” on top of the asthenosphere. – Lithosphere (land) gets moved (like a person being moved on an escalator) Mantle • The region that lies between the crust and the outer core • Thickest of the Earth’s layers • Over 70% of Earth’s volume • Down to 2900 km (1800 miles) • Mostly solid, but… – High temps. and pressure cause it to behave in a plastic (putty) manner. (like thick, hot asphalt) Volcanic MAGMA comes from the mantle Outer Core • • • • • molten (liquid) IRON and nickel (alloy) MOVES / FLOWS like a liquid about 10% sulfur (S) Density: 11 g/cm3 Convective flow of the liquid magnetic iron causes the Earth’s magnetic field Inner Core • • • • Radius 1216 km (754 miles) size of our moon Mostly IRON (Fe) Spins? Extremely high temperature (+3700°C or 6700°F) • Yet it doesn’t melt, it’s Solid! • Immense pressure of the overlying layers prevent the iron from melting. – Average density of 14 g/cm3 Earth’s Layers Solid Liquid Pressure Temp. (check) (check) Most-least Crust X Mantle X Outer Core Inner Core X Most-least 4 4 X 3 3 X 2 2 most most Earth’s Layers Review Name that layer! 1.________: Solid iron and nickel most dense; highest temperature due to intense pressure 2. ________: Liquid iron and nickel, flows to produce Earth’s magnetic field 3._________: Most 70% (thickest layer)Compounds rich in iron, silicon, magnesium, olivene, peridotite; molten magma originates here 4.________: Rigid layer of lighter rocks 5. ________________: Crust and uppermost mantle 6. ________________: Lithosphere floats on a thin, slush-like layer of the mantle (UPPER MANTLE). Lava lamp Answers Inner Core 1.________: Solid iron and nickel most dense; highest temperature due to intense pressure Outer Core 2. ________: Liquid iron and nickel, flows to produce Earth’s magnetic field Mantle 3._________: Most 70% (thickest layer)-Compounds rich in iron, silicon, magnesium, olivene, peridotite; molten magma originates here Crust 4.________: Rigid layer of lighter rocks Lithosphere 5. ________________: Crust and uppermost mantle Asthenosphere 6. ________________: Lithosphere floats on a thin, slushlike layer of the mantle (UPPER MANTLE). Lava lamp