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? MOTION: Describe the motion that in the model that explains your observations Rocks of Earth’s crust vary in density: granite is less dense, then basalt, peridotite and iron   Molten lava erupts from volcanoes.   Mohorovic found that EQ wave velocities change at about 50 km.   EQ P waves are reflected, bent, velocity decreases and S-waves are stopped.   Earth has a north and south magnetic pole. 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 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. Earth has an OUTER CORE composed of liquid IRON that is flowing creates a magnetic field. 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 The inner core is SOLID iron and nickel Density of Earth’s Rocks Lab Magma video clip Earthquake P and S waves Compass, magnets Rock Lab data Meteorite samples

So….Earth’s 4 layers were determined by physical properties…. Temperatures and pressures (both increase and change with greater depth) 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

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

Re-melted, destroyed, recycled Two distinct types of crust Continental Crust Characteristic Oceanic Crust 35-50 km Thickness 5-12 km Granite (light) Composition Basalt (dark) to 3.8 billion yrs. Geological age to 150 million yrs 2.7 Density 3.0 Ave. +1,000 m Elevation Ave. - 3,000 m No Re-melted, destroyed, recycled Yes Deformed 33% Current distribution 67% *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? silicon (Si) 2. oxygen (O2) 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/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. Crust Mantle Outer Core (check) Liquid Pressure Most-least Temp. Crust Mantle Outer Core Inner X 4 4 X X 3 3 X 2 2 X 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 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 Inner Core Outer Core Mantle Crust Lithosphere Asthenosphere