How do we know about the different layers of Earth's interior when we've never been there?

Transcription

1 Layers of the Earth Layers of the Earth How do we know about the different layers of Earth's interior when we've never been there? Oct 11 6:41 AM Make a note: These layers are inferred based on seismic (earthquake) data. CRUST Forms the Earth s outer skin Contains Oct 18 8:48 AM 1

2 CRUST It is 5 40 km thick Thickest on land called the: Continental Crust CRUST Thinnest on ocean floor called the: Oceanic Crust Made up mostly of Basalt Made up mostly of Granite CRUST The oceanic crust is more dense than the continental crust. CRUST Density of the oceanic crust is 3.0 g/cm 3 Density of the continental crust is 2.7 g/cm 3 O = Si = Al = Fe = Ca = Na = K = Mg = Chemical composition: Oxygen Silicon Aluminum Iron Calcium Sodium Potassium Magnesium CRUST Oct 20 8:36 AM 2

3 Thickest layer of the Earth 40 km 2,900 km below the Earth s surface MOHO Discontinuity (surface where seismic waves change velocity) Boundary between the and the Discovered by Croatian seismologist Andrija Mohorovicic (~1910) Velocity of seismic waves relate to the density of the material they move through (higher density = faster waves) Waves accelerate at MOHO MOHO Discontinuity (surface where seismic waves change velocity) Boundary between the and the Discovered by Croatian seismologist Andrija Mohorovicic (~1910) Velocity of seismic waves relate to the density of the material they move through (higher density = faster waves) Waves accelerate at MOHO crust mantle 3

4 Mantle is sub divided into three sections: Rigid Mantle Plastic Mantle Stiffer Mantle Rigid Mantle Solid layer of very hot rock just below the crust aka The rigid mantle (upper mantle) and ALL of the crust form Lithosphere the Greek: "stone / rock" Plastic Mantle Less viscosity than the rigid mantle resistance to flow Viscosity: ASTHENOSPHERE Makes up the Greek: "weak" LITHOSPHERE floats on top of ASTHENOSPHERE 4

5 Stiffer Mantle Returns to a more solid mantle all the way to the core Outer (liquid) Core Inner (solid) Core CORE Mantle chemical composition: Si, O, Fe, Mg CORE Outer (liquid) Core: Molten metal of thick? and? 2,900 km to 5,150 km below Earth s surface? CORE Outer (liquid) Core: Molten metal of thick iron and nickel 2,900 km to 5,150 km below Earth s surface Pressure Section Removed 5

6 Pressure Section Removed Pressure Section Removed 2900 km 5100 km 2900 km 5100 km CORE Inner (solid) Core: Dense ball of solid metal ( iron and ) nickel 5,150 km to 6,371 km below Earth s surface 5100 km 6300 km ESRT Page 10: Reference Lines Oct 17 12:30 PM 6

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8 As depth increases: Pressure and Temperature increase However, Pressure and Temperature different at rates increase Called the Pressure and Temperature However, Pressure and Temperature different at rates increase gradient Called the Pressure and Temperature 8

9 As Temperature increases faster than Pressure, melting points increase. At lower pressure, things melt at temperatures 9

10 As Temperature increases faster than Pressure, melting points increase. At lower pressure, things melt at higher temperatures As Pressure increases faster than Temperature, melting points decrease. At higher pressure, things melt at temperatures As Pressure increases faster than Temperature, melting points decrease. At higher pressure, things melt at lower temperatures 10

11 We have a density layered planet 3 The Earth has layers chemical composition Each layer is identified by their The more dense elements settled in the Earth 11

12 3 The Earth has layers chemical composition Each layer is identified by their deeper The more dense elements settled in the Earth 12