Earth’s Layered Structure

PHENOMENON: What did you observe? What evidence do you have? OBJECTS: Define the system. What objects are interacting? MOTION: Describe the motion /model that explains your observations Rocks of Earth’s crust vary in density: granite is less dense, then basalt, olivene and iron Ave. density of the crustal rocks ; granite, basalt, olivene is 3.0 g/cc. Yet the average density of the entire Earth is 5.4 g/cc Molten lava erupts from volcanoes. EQ waves were found to reflect, bounce off “something” solid in the center EQ P waves are reflected, bent, velocity decreases and S-waves are stopped. Earth has a north and south magnetic pole. Temperature, density, thickness and P/S wave velocity changes at certain depths: (100 km, 1000 km, 3000 km, 5000 km) Meteorites formed from the same materials at the same time as the terrestrial planets. Some of them are rocky and some are metallic 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. 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 Magma suggests that there is liquid, MANTLE of molten rock under the solid, rocky crust The inner core is SOLID iron and nickel There is a boundary between the solid crust and the liquid (magma) mantle layer. Earth has an OUTER CORE (surrounding an inner solid core) composed of liquid IRON that is flowing and creates a magnetic field. Layers differ based on their depths and compositions (evidence from scientific collection confirms this) The Earth must have ROCKY as well as METALLIC components Density of Earth’s Rocks Lab Spaceship Earth The Universe video clip Earthquake P and S waves (classzone.com ES0402) Spaceship Earth video, Compass, magnets Meteorite samples The story so far…… Figure 8.10, table 8.2 and figure 8.11 homework

Earth’s Layers Solid (check) Liquid (check) Pressure Most-least Temp. Most-least Crust Mantle Outer Core Inner Core X44 XX33 X 2 2 X most most

Earth’s Main Layers Lithosphere/crust Mantle Outer Core Inner Core Inner coreOuter 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 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

Two distinct types of crust Continental Crust Characteristic Oceanic Crust kmThickness5-12 km Granite (light)CompositionBasalt (dark) to 3.8 billion yrs.Geological ageto 150 million yrs 2.7Density3.0 Ave. +1,000 mElevationAve. - 3,000 m No Re-melted, destroyed, recycled Yes DeformedNo 33%Current distribution67% *Origin of continental crust is the partial re-melting of original oceanic crust

Asthenosphere (asthenos- weak) upper mantle 100 km to 660 km Soft, solid/liquid, weak in structure, constantly moving

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

Most of the Earth's mass is in the mantle is composed of what 5 elements? 1.silicon (Si) 2. oxygen (O 2 ) 3. Magnesium (Mg) 4. Aluminum (Al) 5. Iron (Fe)

Outer Core molten (liquid) IRON and nickel (alloy) MOVES / FLOWS like a liquid about 10% sulfur (S) Density: 11 g/cm 3 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/cm 3

Earth’s Layers Review Name that layer! 1.________: Solid iron and nickel most dense 2. ________: Liquid iron and nickel, flows to produce Earth’s magnetic field 3._________: Most 70% -Compounds rich in iron and silicon and magnesium. 4.________: Rigid layer of lighter rocks 5. ________________: Crust and uppermost mantle 6. ________________: Lithosphere floats on a thin, slush-like layer of the mantle. Lava lamp Inner Core Outer Core Mantle Crust Lithosphere Asthenosphere